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Examples of this relationship are discussed here. Ciliated cells Function To sweep mucus, in which dust and bacteria are trapped, up the bronchi and trachea towards the throat where it is swallowed. How they are adapted to this function Ciliated cells are found lining the walls of the trachea wind-pipe in the respiratory tract. Each cell bears a fringe of minute projections cilia.
The singular of cilia is cilium. How they are adapted to this function The outer part of the cell wall of each root hair cell i. This root hair: To conduct water and ions dissolved salts from the roots to the stem, leaves, flowers and fruits. Xylem vessels are elongated dead cells forming long, narrow tubes, stretching from the roots, via the stem, to the leaves. They are stacked end to end like drain pipes.
Their walls have been strengthened by the addition of the chemical lignin.
As the lignin in the walls builds up, it eventually kills the xylem vessels. There is then no layer of cytoplasm to restrict the flow of water and dissolved salts. Xylem vessels are part of the vascular bundles Figure 2. Vascular bundles help to strengthen a stem since they work like iron reinforcements in concrete pillars. The inner structure of a plant leaf includes two specialised types of cell known as mesophyll cells. These may be long, thin cells that carry electrical impulses from the receptor organs to the central nervous system, or from the central nervous system to the organs that are required to respond the effectors see Chapter 13, Figure Neurones in the central nervous system, especially the brain, are more compact.
The lower cells are called spongy cells and the upper layer are the palisade mesophyll cells Figure 2. The palisade mesophyll cells form the main photosynthesising tissue of the leaf, helped by the fact that they: The cytoplasm of red blood cells contains the pigment hemoglobin, which combines in the lungs with oxygen to become oxyhemoglobin.
This gives them a very large surface area for oxygen absorption. Points 2, 3 and 4 are also relevant to their other function of carrying carbon dioxide. Sperm and egg cells Together known as gametes, these are the cells used in sexual reproduction. They are produced by a form of cell division meiosis that halves the number of chromosomes they possess, that is they become haploid.
In this way, when they unite at fertilisation, the full number of chromosomes the diploid number is restored. Sperms are released in millions at a time to increase the chances of fertilisation. What features do root hair cells and red blood cells have in common and what common purpose do these features serve? One cell working on its own would achieve very little in an individual plant or animal, thus it is usual to find many similar cells lying side by side and working together, performing the same function.
A tissue is therefore: Examples of tissues: Different types of tissue often work together in order to achieve a combined function.
Several tissues working together to perform specific functions form a structure called an organ. Examples of organs: Several different organs may be necessary in order to carry out a particular function. A group of organs with related functions working together in order to perform a particular body function is called an organ system. Examples of organ systems: Worked example Explain how the terms cell, tissue and organ may be applied to the structure of a leaf.
Answer It is easiest to begin with the fact that leaves are made up of a large number of cells. This would then be followed by some different examples of types of cells found in a leaf — for example, palisade cells and, if you have looked up leaf structure, you could include spongy cells, epidermal cells and cells found in the vascular bundles e. The answer should then refer to the fact that the cells are modified for different. Make a list of two different types, other than those mentioned in the text, of cell, tissue, organ and organ system.
Check with your teacher that you have correctly classified you chosen examples. The cells are found working beside many other similar cells, each one of which is modified in the same way and performs the same function.
Such a group of cells forms a tissue — for example, the palisade tissue for making starch during photosynthesis and the xylem tissue for bringing water and ions into the leaf and for supporting the leaf. A leaf thus contains a number of groups of different cells, each group performing its own job, but with each group performing one of the necessary functions of a leaf. Thus, the leaf is an organ, since it have several tissues working together performing specific functions.
Biologists deal with specimens with a wide variety of sizes.
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If a specimen is rare, then a description of it is invaluable to other biologists in particular and other people in general. A drawing is often the best way to record observations, but such a drawing is of little value if it does not give an indication of the size of the object being observed. All drawings of biological specimens should, therefore, include a reference to the magnification of the drawing.
When drawing, measure in mm — avoid cm — so give a measurement as 5 mm rather than 0. Clearly state the linear dimension measured from the drawing over the matching linear dimension measured on the specimen when calculating the magnification, e.
Chapter summary You have learnt the component parts of a cell. You have also learnt how plant and animal cells are similar and how they differ. You know how cells, tissues, organs and organ systems are related. You have learnt how cells are modified to perform different functions. You have also learnt what is required when drawing a specimen. Name the chemicals responsible in each case for the colour of the two cells: Cell A and Cell B. In Table 2. Photosynthesis occurs in the situated in the of the cell.
It uses carbon dioxide absorbed in the leaf. With reference to the kidney, ureters and bladder, explain the difference between the terms organ and organ system.
Movement in and out of cells Learning outcomes By the end of this chapter you should understand the processes responsible for the movement of substances into and out of cells:. Chemicals must be able to move from one part of a cell to another, into and out of a cell and from one cell to another if an organism is to remain alive. Diffusion relies on the fact that all molecules are in a constant state of random kinetic motion, but before diffusion can occur, there must be a concentration gradient of the molecules, that is, a region of their relatively high concentration immediately beside a region of their relatively low concentration.
Diffusion can then be defined as the net movement of molecules and ions from a region of their higher concentration to a region of their lower concentration, down a concentration gradient as a result of their random movement. The energy that causes the movement of chemicals is the kinetic energy that results from the movement of molecules and ions.
Only those molecules small enough to pass through the cell surface membrane are able to pass in and out of a cell. Oxygen first diffuses in solution from the photosynthesising cells into the water film surrounding the cells. The loss of water vapour in this way is called transpiration. In animals 1 The movement of oxygen after it has dissolved in the moisture lining the air sacs of the lungs through the walls of the air sacs alveoli into the blood.
In all the examples given here — apart from water vapour, the substance that diffuses has first dissolved in water i. How many examples of diffusion can you think of — first in the world around you, then in plants and in animals? Check your list with your teacher to see how many of your examples were correct. This is achieved by the absorbing structure being long and thin e. The effect of surface area Apparatus: A petri dish Three cork borers of different sizes Two medium-sized beakers Two dropping pipettes Safety goggles and thin protective gloves Materials:.
Following the instructions on the bottle, dissolve some agar in hot water. When it has dissolved, using a pipette, add a few drops of phenolphthalein indicator to the agar solution. Pour the pink agar solution into the petri dish and allow it to cool and set in a refrigerator.
Wearing the gloves and goggles, fill the second beaker to a depth of at least 3 cm with the. For this reason, respiratory surfaces, for example, the walls of the alveoli in the lungs that absorb oxygen and release carbon dioxide are only one cell thick. Using each cork borer, in turn, bore out three cylinders of agar from the petri dish. If you have trouble in removing the agar from the cork borers, you can, instead, using a sharp blade, cut the agar into three different-sized cubes, which you should measure carefully.
The effect of temperature The investigation of surface area previously can be adapted to demonstrate the effect of temperature on diffusion.
As before Method: Wearing the gloves and goggles, fill three beakers with the hydrochloric acid each to a depth of 3 cm. Place one of the three beakers in the container of ice and water, one on the bench at laboratory temperature and one in the water bath, leave for 10 minutes. Bore three cylinders of agar each with the same cork borer or, cut three identical cubes of agar, as described previously. Results and explanation: Thus diffusion occurs faster the higher the temperature.
The effect of concentration gradient Investigation 2 can be adapted to demonstrate this effect. Although these concentrations are suggested, the investigation should work well enough with three other differing concentrations.
As in Investigation 2, but no container of ice and water or a water bath are required. All three beakers should be kept at the same laboratory temperature. Bore three cylinders each with the same borer, or cut three identical cubes of agar.
The agar in the most concentrated acid is first to lose its colour and last to lose its colour in the least concentrated. The effect of distance This can be easily investigated by using two glass containers of significantly different volume. Each is filled with water, then placed side by side and left for the water to become still.
Two of three drops of a concentrated solution of potassium permanganate are added, at the same time, to both containers, and the time is noted. The containers are then observed until the water in each of them is uniformly purple in colour and the time for each is recorded.
It takes longer for the water in the larger container to become uniformly coloured. It is not just that the potassium permanganate has further to travel, but also that its concentration gradient is progressively declining as it spreads out in the container.
The effect of distance can also be demonstrated by spraying aerosol deodorant, or fly-killer at one side of a classroom, and asking students to note the time taken before they can smell it. The further away they are, then, perhaps not surprisingly, the longer it takes for the chemical to reach them by diffusion through the air.
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The pores in the cloth would form no obstruction to the movement of the molecules in either direction. All cell membranes are partially permeable, therefore water will move into or out of cells by osmosis depending on the concentration gradient of water molecules inside and outside the cell. Dilute solutions, which have a relatively large number of water molecules, are said to have a high water potential i.
Concentrated solutions, with fewer water molecules, are said to have a low water potential. During osmosis, since water molecules are in a constant state of motion, they will be moving through the partially permeable membrane in both directions, but always more will be moving from where they are in greater concentration towards the lower concentration.
Osmosis can then be defined as the net movement of water molecules from a region of higher water potential a dilute solution to a region of lower water potential a concentrated solution , through a partially permeable membrane. This specialised case of diffusion is called osmosis and the separating membrane is described as partially permeable. The cell sap of root hair cells has relatively low water potential. Soil water has a relatively high water potential.
Thus water will move into the vacuole of root hair cells by osmosis Figure 3. The cell wall offers no obstruction to the passage of water, since cellulose, of which it is made, is completely permeable. But, where the walls of neighbouring cells touch, water can pass into the root by simple diffusion — through the cellulose of the cell walls. Osmosis will thus cause water to move into that cell from the root hair cell.
This process continues. Visking tubing partially permeable membrane tightly tied at the bottom and around the glass tube. The pressure caused by the water pushing outwards on the cell wall turgor in plant cells helps:. The effect of osmosis on plant cells The intake of water by osmosis Water will always tend to enter plant root cells by osmosis, since soil water will always be likely to have a higher water potential than cell sap Figure 3.
As the vacuole thus increases in volume, it increasingly presses the cytoplasmic lining of the cell against the flexible, box-like cell wall. This pressure is called turgor pressure and it gives plant cells a firmness called turgidity. This can be demonstrated in the laboratory using a piece of Visking tube that has been tied tightly at its lower end, that contains sucrose solution, and is tied tightly at its upper end to a piece of glass tubing.
The apparatus is then supported in a beaker of water as shown in Figure 3. The water potential inside most animal cells is often the same as the solution in which the cells are naturally bathed.
See Chapter 12, Kidney Function. Thus there is little movement of water by osmosis into or out of the cell. However, a red blood cell placed in a solution with a relatively high water potential, starts to take in water by osmosis, and since there is no cell wall to resist the increased pressure that results, the cell bursts. The loss of water by osmosis Plant cells placed in a solution of relatively low water potential, lose water from their vacuoles.
As a result they lose their internal pressure since the cytoplasm is no longer being forced against the inelastic cell wall. They become soft Figure 3. When a cell loses its internal pressure, it is said to be flaccid. Animal cells placed in solutions of lower water potential, lose their shape and what turgidity they have, as water moves out of their cytoplasm. Animal cells placed in a solution with a high water potential e. They have no inelastic cell wall to resist the intake and to make them turgid, so they burst.
Pressure is no longer exerted on cell walls the cell becomes flaccid and decreases in length and width. Such a condition is called plasmolysis. This ensures that the concentration of chemicals in the cell cytoplasm remains constant and, therefore, so too is the rate of metabolism.
Two large potatoes Two containers e. Then cut all the strips to the same length and record that length. Fill one beaker to within 2 cm of the top with water, and the other with a concentrated sucrose or sodium chloride solution. Submerge three of the potato strips in each of the beakers. For the strips in the sucrose or salt solution, the water potential of the cell sap is higher than the water potential of the solution, thus water has moved out of the cells.
The cells have decreased in size and lost their firmness. Thus the strips are shorter and are soft to the touch. The strips in the water will have increased in length and will be firm to the touch; those in the sugar or salt solution will have decreased in length and be soft to the touch.
For the strips in water, the cell sap in the cells of the potato will have a lower water potential. Loss of water from cells makes stems soft and no longer able to support the plant and leaves curl and are less able to photosynthesise. When a plant has access to water and absorbs it by osmosis, its cells become firm as the water enters the cell vacuoles and presses outwards on the cell walls. Like the potato strips, the tissues of the plant become firm and, when this happens in the stem and leaves, the plant is supported and held upright and the leaves are firm and held open to the sunlight for photosynthesis.
Place a fruit sweet between your teeth and your cheek and leave it there for about a quarter of an hour without biting or sucking it. Then remove it and feel the inside of your cheek with your tongue.
Write down a description of how it feels and attempt an explanation. Why, when a plant cell and an animal cell are both placed in water, does only the animal cell burst? Note the texture of the strips. Why do the leaves and stems of a plant shoot, whose cells have started to undergo plasmolysis, begin to droop?
Sometimes, a living cell may be in need of a chemical, even though there is a lower concentration of it outside than inside the cell. In such a case, the chemical would have to be absorbed against a concentration gradient.
This can be achieved only with the use of energy released by respiration inside the cell in conjunction with the cell membrane. This energy allows the cell to absorb the chemical through the cell membrane and prevent any of the chemical already inside the cell from leaving. This process is called active transport and is defined as the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.
The energy released in respiration is stored in the chemical ATP in the mitochondria. Cells that undergo active transport characteristically have a large number of mitochondria. Ions are thus absorbed by root hair cells by active transport.
The situation also arises in the small intestine of an animal, when digested food such as glucose is absorbed by the epithelial cells of the villi by active transport. This is achieved by proteins, called carrier proteins, that are bedded in the cell membrane Figure 3.
They are the same thickness as the membrane and thus they are in contact with the surrounding of the cell on the outside and the cytoplasm of the cell on the inside. Energy is used to open up a channel on the part of the molecule facing the outside of the cell. The molecule or ion to be absorbed enters the channel and binds to a special site in the centre of the carrier protein molecule.
Each carrier protein will bind to only one particular molecule. Thus, like enzymes, they are specific. Further energy is then used to close off the opening to the outside of the cell, and to open up a similar channel, this time into the cytoplasm of the cell.
The carrier protein then reverses the process, again using energy so that it is available to take in another molecule. Describe how the structure of a cell membrane is adapted to the process of active uptake. These molecules fit loosely together leaving minute channels between them extending from the outside of the cell to the cell cytoplasm.
Suggest how these channel proteins may play a part is the processes of diffusion and osmosis. Answer The question calls first for a realisation that there is a special structural feature of the cell membrane making it able to undergo active uptake. All energy within a cell is initially released by respiration and, in this case,.
First the carrier protein opens to the outside and allows the molecule to be absorbed to attach bind to the protein. Only one type of molecule will bind as the site is not suitable for any other molecule.
The protein then changes shape again again using energy — closing the outer opening, and opening into the cytoplasm of the cell. The molecule is released into the cell cytoplasm, then changes shape again, closing to the inside and opening to the outside ready to bind with another molecule to be absorbed.
Note that the complete cycle of carrier protein movements is described as a continuous process. The channel proteins would provide the pores. However, the size of the pores might prevent larger molecules from entering. Chapter summary You have learnt how cells are involved in the processes of diffusion, osmosis and active transport. Describe what will happen to the tubing and its contents over the next 20 minutes. The structure of important chemicals found in organisms, including fats, proteins, carbohydrates and DNA.
The structure of the different chemicals that organisms use in their nutrition How to carry out food tests to detect their presence.
Carbohydrates Carbohydrates are organic chemicals containing the elements carbon, hydrogen and oxygen only.
The ratio of atoms of hydrogen to atoms of oxygen in a carbohydrate molecule is always 2: Carbohydrates with large molecules, such as starch, glycogen and cellulose, are insoluble.
They are synthesised in living organisms by linking together molecules of simple sugar glucose. Large carbohydrate molecules can be broken down into simple sugars. Smaller carbohydrate molecules are soluble and occur as: Fats are organic chemical substances that contain the elements carbon, hydrogen and oxygen only. This time, however, the ratio of H to O in the molecule is very much higher than 2: They are all insoluble in water and are formed by the joining of a glycerol molecule with fatty acid molecules.
Proteins Proteins contain the elements carbon, hydrogen, oxygen and nitrogen and often other elements such as sulfur and phosphorus. They are large, usually insoluble, molecules that are built up from simple, soluble units known as amino acids, of which up to 20 are used in the production of protein in living organisms.
Figure 4. Amino acids are of different sizes and shapes, thus, when linked together to form protein molecules, the proteins formed will also be of different shapes. The tests are shown in Table 4. This structural difference is very important when the protein in question is an enzyme since part of the molecule, known as the active site is of exactly the right shape to fit the molecule the substrate molecule of the chemical reaction that it will catalyse.
Answer a It is best to split this part into its two natural sections — similarities and differences. The first similarity is that they are both sugars and they are both soluble so that they can be more easily moved from place to place within an organism.
They will therefore both also be carbohydrates — a term you should explain. The clue is, again, in the word: Some carbohydrates can be very large molecules, but these sugars are comparatively small ones.
The differences are that one, glucose, is a simple sugar and is the basic unit of many larger carbohydrates such as starch. Sucrose is a complex sugar and one molecule of sucrose C12H22O11 is approximately twice as big as one molecule of glucose C6H12O6. Glucose is a reducing sugar but sucrose is neither a reducing nor a simple sugar.
You are asked how you would distinguish between them, so you will need to give a description of the test and state the result you would expect. NB If you mention a bunsen burner for heating, you would be advised also to mention the use of goggles. How test is carried out a dried sample of the substance to be tested is mixed with ethanol, which is then poured into a testtube of water.
When performing ethanol emulsion test, the test is more reliable if a dried sample is used, but if it is not possible to dry the sample, then the ethanol drained from it may already be cloudy, indicating the presence of a fat. How test is carried out add equal volumes of solution 1 and 2 to a solution of the substance to be tested.
Biuret 1 contains sodium hydroxide that is harmful to the skin and thus appropriate safety precautions should be taken. State the observed colour and the conclusion you draw from that result. Another DNA Chromosomes, situated in the nuclei of all living cells except bacteria, which have no true nucleus have, as their major component, the chemical substance DNA. There are only four bases, known by their initial letters A, T, C and G, and the sequence in which they occur in one of the two DNA strands is responsible for the sequence of amino acids in the protein molecules that are made in the cell.
Since the sequence of bases on a DNA molecule is likely to be different for each sexually produced individual, it follows that no two individuals will make protein molecules with exactly the same sequence of amino acids. What word is used for organisms containing only one cell?
Give an example of a one-celled organism. What word is used for organisms made of many cells? What structure controls the passage of substances into and out of a cell?
In what state must all chemicals be before they can enter or leave a cell? What is the jelly-like substance where chemical reactions occur in a cell? What is the correct term for the chemical reactions in a cell? Whereabouts in a cell are chromosomes found? What do chromosomes contain? Of what chemical are chromosomes made? DNA What makes up protoplasm? What is the space in the centre of a plant cell? What does the space in the centre of a plant cell contain? What is the name of the box in which a plant cell is contained?
Biology Notes.pdf - CIE IGCSE BIOLOGY(0610 Contents...
What chemical is this box made of? Name the green structures in photosynthesising cells. What pigment do they contain? V Preface Here is how you can test yourself on the labels to a diagram.
VI People vary as to how long they can work at a stretch. You may find the following advice useful: Preface 2. Finally, good luck with your revision. This method can work. I know, because it did so for me! Ian J. Burton 4. VII Classification Learning outcomes Learning outcomes — set the scene of each chapter, help with navigation through the book and give a reminder of what's important about each topic.
By the end of this chapter you should understand: The characteristics of some invertebrates How to use the binomial system for naming organisms Viruses, prokaryotes bacteria , protoctists and fungi How living organisms are classified The construction and use of a dichotomous key The characteristics of some vertebrates 1.
Glossary terms — terms in green can also be found in the Glossary Breathing and respiration are not the same thing. An animal that gets its energy by eating plants is an herbivore or primary consumer.
Progress check How to use this book Practical skills — reinforce your practical knowledge and skills with clear explanations and diagrams. Progress check questions — check cytoplasm. How the iris muscles alter the shape of the lens Answer Note that the complete cycle of carrier protein Near and distant objects 1 2 3 effect of work to Diffusion requires pores in the membrane before molecules can enter. Chapter summary 1 Light sensitive cells in the retina detect the light intensity.
IGCSE Biology Revision Guide
The characteristics of living organisms The characteristics of some invertebrates How to use the binomial system for naming organisms Viruses, prokaryotes bacteria , protoctists and fungi How living organisms are classified The construction and use of a dichotomous key The characteristics of some vertebrates 1. TIP Plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water. The binomial system is useful because: Progress check 1. How many bases are there?
Chapter 1 Classification For many years, the classification of organisms was based on studies of their morphology, that is, their outward appearance, for example, the number and type of limbs, or the shape of the flowers produced by a plant. The distinguishing features of these two kingdoms are as follows: All fish share the following characteristics Figure 1. Worked example All arthropods have the following features: One pair of antennae One pair of legs per segment first pair of antennae each one divides other limbs underneath abdomen head and thorax cephalothorax Figure 1.
A birds B insects C mammals D reptiles Occupying a position below the plants and animals in the evolutionary tree, the prokaryotes, protoctists and the fungi each form their own kingdoms see earlier.
Other features present in cells 3 The nucleic acid is surrounded by a protein coat known as the capsid. Ribosomes are: Protoctista Prokaryotes are truly living organisms, with the following characteristics Figure 1. These are a group of largely microscopic, truly living organisms. DNA no nucleus Figure 1. An organism possesses xylem but never produces flowers.
Which of the following will it be? Yes No go to 2 go to 3 2 Does it have a nucleus? Yes No protoctist bacterium 3 Does it have hyphae? Yes No fungus go to 4 4 Does it have cell walls? Yes No plant animal When identifying one organism from amongst a large number of possibilities, the most effective dichotomous key asks questions that each time divides the remaining possibilities into roughly equal halves.
Six different geometrical shapes, identified by the letters A to F are shown in Figure 1. You are able to list the five classes of vertebrate and know how to distinguish between them.
You have learnt the differences between the two classes of flowering plant. You have learnt how to use and also to construct a dichotomous key for identifying organisms.
A B C As an example, the appropriate boxes for arthropod A have been ticked for you. Chapter 1 Classification Exam-style questions Figure 1. One pair of antennae One pair of legs per segment a Name two other groups of arthropod. It is a carnivore that lives on land and, 14 compared with most other arthropods, its outer body covering is thin and permeable.
The structure of animal and plant cells and the differences between them How certain plant and animal cells are adapted to the functions they perform 2. This contains a number of chromosomes made of the chemical DNA. NB Cytoplasm and nucleus together may be referred to as protoplasm. Progress check 2. DNA DNA forms genes that are responsible for programming the cytoplasm to manufacture particular proteins.
Matrix outer membrane inner membrane Mitochondrion Figure 2. Sap vacuole The importance of this structure is to contain a solution more concentrated than the solution in the 17 Similarities and differences between plant and animal cells are shown in Table 2.
TIP Chapter 2 Cells soil water around the plant. Cut a cube of fresh liver, in section, approximately 1. Chapter 2 Cells Progress check 2. Functions 1 To conduct water and ions dissolved salts from the roots to the stem, leaves, flowers and fruits.
Support 1 Their walls have been strengthened by the addition of the chemical lignin. TIP Chapter 2 Cells How they are adapted to these functions Vascular bundles help to strengthen a stem since they work like iron reinforcements in concrete pillars. To carry oxygen around the body. Function 1 2 3 The cytoplasm of red blood cells contains the pigment hemoglobin, which combines in the lungs with oxygen to become oxyhemoglobin.
They have a biconcave shape, increasing their surface area for absorption still further. The sperm This is the male gamete, it is made of: B They contain many fibrils. C They have strengthened cell walls. D They possess many cilia. The egg cell or ovum This is the female gamete with the following features: The increasing order of cell organisation found within any living organism is thus: P the eye Q the muscles in the intestine wall Different types of tissue often work together in order to achieve a combined function.
R a flower Which shows the level of organisation in these three structures? TIP Remember, if the specimen is large, then the magnification will almost certainly be less than 1. Progress check 3. Some examples of diffusion are described here. A petri dish Three cork borers of different sizes Two medium-sized beakers Two dropping pipettes Safety goggles and thin protective gloves Materials: This process continues glass tube sucrose solution rises in the glass tube as water passes from the beaker through the partially permeable membrane by osmosis water enters vacuole by osmosis vacuole increases in volume and pressure pushes against cytoplasm cytoplasm pushes against cell wall — stretching the cell and making it firm turgid Figure 3.
The pressure caused by the water pushing outwards on the cell wall turgor in plant cells helps: Chapter 3 Movement in and out of cells until water molecules reach the xylem vessels in the centre of the root and are then transported away to the stem. For the strips in water, the cell sap in the cells of the potato will have a lower water potential The effect of the gain or loss of water on a plant Loss of water from cells makes stems soft and no longer able to support the plant and leaves curl and are less able to photosynthesise.
Which part of Figure 3. All energy within a cell is initially released by respiration and, in this case, the energy is used to move the carrier proteins. Chapter 3 Movement in and out of cells Worked example Diffusion requires pores in the membrane before molecules can enter.
You have learnt how to demonstrate these processes experimentally. You have learnt how these processes are important to living structures. You have also learnt about the factors that affect them.
Exam-style questions 1 Describe how different substances in a leaf move by diffusion during a hour period. The structure of important chemicals found in organisms, including fats, proteins, carbohydrates and DNA 4.
Progress check 4. How test is carried out Chapter 4 The chemicals of life This structural difference is very important when the protein in question is an enzyme since part of the molecule, known as the active site is of exactly the right shape to fit the molecule the substrate molecule of the chemical reaction that it will catalyse. TIP Progress check 4. What reagent has been used and what chemical is present? Result Table 4. Another 36 important constituent of foods is vitamin C and there is a test that is used to decide whether a food contains vitamin C.
Cambridge University Press Education. Published on Oct 26, This is the characteristics of life is the viruses.
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The chemical reaction unlocks thesize then stop, there will be many organisms living together. In some chemicalothers energy forgrows conversion into other formsthroughout is while continuously their way they will all be interconnected by way of different respiration. Only A network of interconnected food chains is known as in size. Growth inbacteria dry massWhile by an all food chains and thus all food webs begin This includesinvolves energy froman theincrease respiration of with aDry producer, food webs may begin with several and fungi thatineventually decay dead increase cell number ororganisms.
In order to maintain or Inincrease a food chain or food web, producers are eaten by their numbers, all organisms have the ability to make consumers. Much of the energy is still present in the faeces and more the same A consumer in a food chain is an organism that gets its some in theof nitrogenous wastekind. This energy is available to decomposers. An animal that gets its energy by eating plants is an herbivore or primary consumer.
Five trophic levels are usually the limit for a food chain Figure Thus all consumers above the level of herbivore, that is, all meat eaters, are carnivores. The longer the food chain, the less the energy available to the top carnivore at the end of the chain.
Magnesium is the central atom in a chlorophyll molecule. Plants lacking in magnesium ions are unable to make chlorophyll and thus their leaves are yellow in colour a condition known as chlorosis. Photosynthesis produces the carbohydrate with its stored chemical energy. Almost all other forms of life rely on carbohydrate, although plants may convert this carbohydrate into protein or fat before it is passed on.
Progress check Images formed to prevent 1 The circular ciliary muscles relax, increasing their Culture solutionsare not converted into on this part of the retina the growth of culture circumference. Method: single-celled solution impulses and relayed to the brain. This region green algae Two seedlings or small cuttings, with the same 2 The suspensory ligaments are pulled tight.
We are not number of leaves, are selected from a quick usually ofheld theinblind since the blind Figure 6. How to use this book Practical skills — reinforce your practical knowledge and skills with clear explanations and diagrams. It is easier to see the outline of an object in dim light by looking to the side of it.
Can you explain why this is? Therefore, it is more accurate to call it the iris reflex. Progress check questions — check cytoplasm. That feature is the presence of carrier proteins.
Since they have to work against a concentration gradient there may be a lower concentration of the chemical to be absorbed outside than inside the cell then energy must be used. All energy within a cell is When a person is respiration viewing aand, near object: initially released by in this case, movements is described as a continuous process. How the iris muscles alter the shape of the lens Answer Note that the complete cycle of carrier protein Near and distant objects 1 2 3 effect of work to Diffusion requires pores in the membrane before molecules can enter.
Theiris channel would The has proteins an antagonistic arrangement provide the pores. However, the size of the pores radial muscles. Water is a small molecule and thus could enter by osmosis, and the pores may be too small to allow larger molecules to enter — making the membrane semi-permeable.
Chapter summary 1 Light sensitive cells in the retina detect the light intensity.
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With reference to diffusion and osmosis, explain the results of this experiment. Explain how a plant root absorbs from the soil: i water  ii essential mineral ions that are in very short supply.
The publishers would be grateful for any omissions brought to their notice for acknowledgement in future editions of the book. The authors and publishers acknowledge the following sources of copyright material and are grateful for the permissions granted. The one group of organisms that does not show all the characteristics of life is the viruses. Thus they are considered to be on the border between living and non-living. It is thus defined as an action by an organism or part of an organism causing a change of position or place.
This is a chemical reaction that takes place in living cells. The glucose molecule contains energy in the form of chemical energy, which is converted into other forms for use in doing work — such as electrical energy in nerve impulses.
This is the ability to detect and respond to changes in the environment known as stimuli. The stimuli may be from the internal environment — for example, the effect of hormones on a cell or tissue, or from the external environment — for example, light. The internal environment is a term that refers to the conditions inside an organism. Sensitivity is also the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses. It is customary for organisms to start life small in size and gradually become larger with time.
Some organisms grow to a certain size then stop, while others grows continuously throughout their lives. Growth is defined as a permanent increase in size. Growth involves an increase in dry mass by an increase in cell number or cell size or both.
Dry mass is the mass of all the components within an object except any water present. In order to maintain or increase their numbers, all organisms have the ability to make more of the same kind. This is the removal from organisms of toxic materials and substances in excess of requirements. In order to provide the raw materials and the energy for all the other characteristics of life listed previously, organisms must take in energycontaining materials that are required for growth and development.Jared Diamond.
This is the removal from organisms of toxic materials and substances in excess of requirements. Both names are always underlined when handwritten and appear in italics in print. Andy Hirsch. Please review your cart. Plants lacking in magnesium ions are unable to make chlorophyll and thus their leaves are yellow in colour a condition known as chlorosis. This can be demonstrated in the laboratory using a piece of Visking tube that has been tied tightly at its lower end, that contains sucrose solution, and is tied tightly at its upper end to a piece of glass tubing.
NB Some prokaryotes contain a loop of DNA called a plasmid — a feature sometimes employed in biotechnology. How they are adapted to this function Ciliated cells are found lining the walls of the trachea wind-pipe in the respiratory tract. Dry mass is the mass of all the components within an object except any water present.