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Transcript
VCE Biology Unit 1: Course Content Revision: Unit 1 Biology Cells Basic Cell Theory: All organisms are made up of cells All cells come from previously existing cells Distinguish between eukaryotic cells and prokaryotic cells o Eukaryotic cells have a membrane bound nucleus and other membrane bound organelles o Prokaryotic cells lack a membrane bound nucleus Be able to recognise the main organelles within cells Cell wall Cell membrane Nucleus Mitochondrion (pl mitochondria) Chloroplast Endoplasmic reticulum Ribosome Golgi body and vesicles Vacuole Structure of the cell membrane: that it is a phospholipid bi layer with proteins embedded. Protein channel Phospholipid bi layer The membrane is SEMI PERMEABLE, allowing some materials to cross and not others. Materials that cross the membrane will cross in one of the following ways: If the molecules are small and non charged they can pass through small pores in the membrane eg. oxygen, carbon dioxide, water If the material is lipid soluble it can dissolve in the lipid bilayer and cross their membrane by diffusion eg. Alcohol, ether, anaesthetic The molecules or ions can be carried across by transport proteins along a concentration gradient by facilitated diffusion eg. Glucose into a red blood cell. The molecules or ions can be carried across by transport proteins actively (against a concentration gradient). This requires the input of ATP (energy) by the cell. eg. Uptake of glucose from the intestine, reabsorption of glucose and amino acids from the kidney proximal convoluted tubule of the kidney nephron, uptake of many mineral ions from the soil solution. The function of each of the major organelles: The role of chloroplasts with regard to photosynthesis and the role of the mitochondria in relation to aerobic respiration are of particular importance. Cell specialization: Relate the number and type of each organelle present in a specialized cell to the overall function of the particular cell type. Distinguish between plant cells and animal cells. Plant cells have a cellulose cell wall and a large permanent vacuole (not just vacuole) which are not found in animal cells. SOME plant cells also have plastids such as chloroplasts (if they are photosynthetic cells), chromoplasts (for storage of colourful pigment- petal cells), or leucoplasts(to store starch- eg. Cells in banana, or potato) NOT all plant cells are photosynthetic thus not all plant cells make their own food. e.g. cells of the epidermis, cell in the cortex and pith of the stem. Not all plant cells contain chloroplasts- but if the cell does contained chloroplasts it cannot be an animal cell. 1 VCE Biology Unit 1: Course Content Side note: Keep in mind that cell types other than plant cells have cell walls. Single celled organisms (kingdom: Protoctista) that are “plant like” eg. Euglena, have cell walls and these are also made of cellulose. The reason they are not members of the Plant kingdom is that they are only one cell big and by definition plants are multicellular organisms showing tissue specialization. Fungi are NOT plant cells, yet they do have a cell wall. Their cell wall is composed of chitin, rather than cellulose as it is in a plant cells. Bacteria also possess a cell wall; however it is composed of a complex polysaccharide other than cellulose.) Microscopy skills: in particular magnification, size, scale, field of view, sharpening images, getting more contrast in the image(e.g. Adjusting the diaphragm aperture)and benefits of staining materials need to be understood. Definitions of diffusion and osmosis: application of these processes. Note that Osmosis refers to movement of only WATER across a SEMI PERMEABLE membrane, along a concentration gradient. The terms hypotonic, hypertonic and isotonic and the effect of placing both plant and animal cells in each type of solution. The terms turgid, plasmolysed and flaccid with respect to plant cells. You should be able to recognise cells in each state above and label parts of a plant cell accordingly. A very good understanding of the concept of large exposed surface area and surface area to volume ratio is required. Be careful with the expression of this ratio. Eg. All exchange surfaces have a relatively large surface area. Single cells organisms or flat organisms have a large expose body surface to their body volume. NOTE: While a large surface area to volume ratio is often a structural adaptation- sometimes it is an advantage to have a relatively small surface area to volume ratio. Eg. A desert frog will be fairly spherical in shape, and will have a relatively small skin surface(compared to its volume) over which water can be lost via evaporation from its body, which is very advantageous in an environment that is very dry, and where water is thus scarce. Energy in cells: ATP: form of energy available for immediate use by cells. ATP is formed from ADP and inorganic phosphate during the process of respiration. (the energy to produce ATP comes from the breakdown of organic compounds usually glucose (or could be fatty acids or amino acids). ATP is produced by the process of respiration which can be anaerobic (in the absence of oxygen) or aerobic respiration Equation for aerobic respiration C6H12O6 + 6O 2 Glucose 6CO2 oxygen + 6H2O + 36ATP carbon dioxide water energy (Anaerobic respiration involves the breakdown of glucose without oxygen. It occurs in the cytosol, produces less ATP ( 2 molecules instead of 36) and additional products ( lactic acid in animal cells, and ethanol and CO 2 in plant cells) Plant nutrition Structure and Function Green plants can make all the materials they need from oxygen, carbon dioxide, water and inorganic nutrients (mineral ions) Plants manufacture organic matter (glucose, amino acids, fatty acids) via photosynthesis 6CO2 + Carbon dioxide 12H2O water chlorophyll light C6H12O6 + glucose 6O2 oxygen Or 6CO2 Carbon dioxide + 6H2O water chlorophyll light C6H12O6 + glucose 2 6O2 oxygen + water 6H2O VCE Biology Unit 1: Course Content The top equation is actually a better representation of the process (because it shows that water is both a reactant and product in the process), but if you are having difficulty remembering this equation and find simplified one easier (as it is the reverse of aerobic respiration equation) then remember this one. CO2 needed comes from two sources: the CO2 produced by plant cells via respiration and if more is needed in addition to this it is taken up from the air surrounding the plant through openings called stomata (via diffusion) H2O needed comes from the soil solution via xylem in roots and stem (as do mineral ions) Light: The blue and red wavelengths of light are the main wavelengths used in photosynthesis Role of the roots and root hairs: active uptake of most mineral ions, uptake of water by osmosis along a water concentration gradient. Role of the stem and the leaves and the structure of each. Location of tissues in vascular bundles (xylem/phloem/cambium) in each, location of pith, cortex and epidermis in stem and root. Location and appearance of cuticle (this is the waxy non cellular layer that reduces water loss from a leaf surface), epidermis, palisade mesophyll, spongy mesophyll, guard cells (2 making up each stoma) Distinguish between monocotyledons and dicotyledons in terms of root, stem structure and leaf venation. Transport of carbohydrates (in the form of sucrose) is in phloem via translocation. Phloem structure (sieve tube cell and companion cells) and process of translocation from source to sink. Transport of water and mineral ions is in xylem (via transpiration). Xylem structure and movement of water in xylem (e.g. adhesion, cohesion, root pressure, evaporation from the leaf surface) Wilting occurs when water loss from a plant exceeds water uptake. When might this happen? Adaptations of plants that help reduce water loss. (thick cuticle, stomata that open during the night, rather that during the day) Plants store carbohydrates (usually as starch), lipids and proteins. Animals make use of these stores for their own nutrition. Structure and function in animals Nutrition: Nutrients are substances obtained from the surrounding environment, which are required by an organism to carry out its normal functions of activity, maintenance and reproduction. Carbohydrates are made of chains of monosaccharides: Amylase is the enzyme group that digests starch. Cellulase breaks down cellulose. Lipids – triglycerides are composed of a glycerol unit and three fatty acids. ( not in a chain) Lipases break down lipids into their building blocks. Proteins are composed of amino acids and are broken down by protease enzymes. Nucleic acids are composed of nucleotides and are broken down by nucleases. Animals cannot make their own organic molecules. They must obtain them in their food. Their diet must provide carbohydrates, essential amino acids, vitamins and minerals. Water is also essential. The process of digestion is to break down complex food substances into molecules small enough to enter cells. Chemical digestion involves specific enzymes breaking apart food molecules. Mechanical digestion is the physical breakdown of food into smaller pieces. Its purpose is to increase the surface area available for enzymes action. Unlike chemical digestion, mechanical digestion does not chemically change food molecules. The mammalian digestive system consists of the mouth, oesophagus, stomach, small intestine(duodenum then ileum), and large intestine and associated glands (salivary glands: secrete saliva, the pancreas secretes: bicarbonate ions and enzymes and the liver: produces bile which is stored in the gall bladder). Food ingestion, mechanical digestion and chemical digestion of starch occur in the mouth. Different types of teeth are present in the mouth. Each type; e.g. canine (tearing), incisor (biting), molar(grinding) have a special structure to enable them to perform a particular role. Food passes along the oesophagus and intestine by peristalsis. Chemical digestion of protein begins in the stomach, which is strongly acidic, providing the correct pH for the action of the digestive enzyme pepsin that operates in the stomach. (due to HCl that is released). (gastric lining of stomach secretes pepsinogen (inactive form of the enzyme pepsin) which becomes the active enzyme pepsin). The gastric lining of the stomach also secretes mucus, which coats the living of the stomach and offer protection against the acid and enzymes inside the stomach. 3 VCE Biology Unit 1: Course Content Bile(made in the liver), which emulsifies fats/lipids, is released into the duodenum via the bile duct. Bile is NOT an enzyme and doesn’t chemically break fats down. Emulsification is a physical process that forms large masses of lipid into small globules, thus increasing the surface area of fat exposed for chemical breakdown by lipase. Chemical digestion of lipid begins in the small intestine. (your text book talks about gastric lipase. At this point in your study we will not consider gastric or lingual lipase) Enzymes secreted from the wall of the small intestine and from the pancreas catalyse the further chemical breakdown in the small intestine. Final digestion of food occurs in the small intestine, which is usually slightly alkaline (due to bicarbonate ions released by the pancreas). Most of the enzymes that function in the duodenum are secreted by the pancreas. Only a few are produced in the wall of the small intestine.(one of these is lactase) Most absorbed substances are actively absorbed across the wall of the small intestine. Structure of villus (and microvilli….you should be able to distinguish between these)and its relation to function of the intestine needs to be considered. ( What materials are absorbed into capillary or lacteal) . Water, lipids and alcohol diffuse passively. Most absorption occurs in the small intestine. Further absorption of some materials occurs in the large intestine, particularly of water, and vitamins. (bacteria which naturally inhabit the colon produced some vitamins.) Large intestine consists of the colon(ascending, transverse and descending colon AND the rectum). Storage of faeces is the role of the rectum and elimination is controlled by the anal sphincter muscle. Cellulose is the major component of plants, but animals do not produce the enzyme cellulase required for its digestion. Some microorganisms are able to ferment cellulose and enable herbivores to obtain adequate nutrition from plant matter. In herbivores these microorganisms are often located in specialize parts of the alimentary canal such as the caecum. Symbiotic bacteria in humans supply important vitamins. Long-term treatment with antibiotics can cause vitamin deficiencies. The complexity of an organism’s digestive system can be related to its diet. Organisms that feed of food that requires little digestion (quite simple compounds) will have a very simple digestive system, focused mainly on the function of absorption. Those that have whose food requires a great deal of processing will have more complex systems. Some organisms don’t need a digestive system of any kind. What kind of organisms might this apply to? Secretions of different glands alter the pH along the length of the alimentary canal, so that it is at an optimal ph for the functioning of specific enzymes that are present in each part. Enzymes are biological catalysts that speed up the rate at which a reaction occurs, without being altered in the process. Enzymes are thus reusable. Each enzyme is specific for its particular substrate (substance that it acts on). It has a unique active site. The active site is the part of the enzyme that fits precisely with a particular substrate, like a lock and key. Products are formed. Enzymes can catalyse build up reactions(anabolic enzymes) or breakdown reactions (catabolic enzymes) All enzymes are proteins and thus their structure is damaged by excessive heat, or by alterations in pH in either direction (an increase or decrease in pH from the optimum). In the enzymes structure is permanently changed it is said to be denatured. It will no longer catalyse the reaction. Enzyme driven reactions will be slowed by lowering the temperature, but a decrease in temperature doesn’t actually change the structure of the enzyme. In animals, carbohydrates, fats and some vitamins can be stored. Glucose is stored short term as glycogen in the liver and skeletal muscle, and long term storage of glucose is as fat in adipose tissue. Protein cannot be “stored” if the diet is deficient in protein body tissues are broken down to obtain amino acids needed. 4 VCE Biology Unit 1: Course Content Transport system: Not all organisms required circulatory systems. Those that don’t are small and have a large surface area to volume ratio. Roles/functions of a circulatory system: Focus on the fact that its role is transport of materials around multicellular organisms. It is not to eliminate materials and take them up, these are the roles of other body systems. The circulatory system provides the link between the various tissue of the body and between body systems. What in particular is transported and where needs to be summarized. Open versus closed circulatory systems: how are they similar and how do they differ? Blood: composition: plasma, erythrocytes (red blood cells), leucocytes (white blood cells) and platelets. The structure and function of the various components. A rough idea of the proportions of each. The structures of a red blood cell and how it suits it to its function (outline role of haemoglobin, why it looses its nucleus, why it is so small and flexible? ) What materials are carried to cells in plasma, and on red blood cells Which materials are carried from cells to body in plasma Transport of oxygen and carbon dioxide by blood How the composition of the blood changes as it passes through a bed of capillaries and exchange of material occurs between the tissue and the blood within the capillaries. Mammalian heart- composing muscle type, structure of heart and how it related to the function of each chamber; blood vessels that lead to and from the heart. Function of the heart, how blood moves through the heart and the function of valves. Heart beat: systole(contraction) and diastole(relaxation) Heart rate can be altered by the action of nerves and or hormones and hear beat is controlled by the pacemaker. Relate heart rate to body functioning. The fact that heart rate needs to alter to accommodate changes in the needs of body tissues in the rate of delivery of cellular needs e.g. oxygen/nutrients and removal of waste e.g. carbon dioxide and urea. Compare 4 chambered heart of mammal with 3 chambered heart of frog and 2 chambered heart of fish. Why aren’t they all the same? Structure and function of veins/capillaries/arteries and how structure relates to their function. Be able to distinguish these blood vessels based on both structure and function A brief outline of the role of the lymph system. What are its main structures and roles? Excretion: define excretion in terms of elimination of metabolic waste(carbon dioxide and nitrogenous waste in particular) If these are not removed effectively death will result. Respiratory system: removal of carbon dioxide (also uptake of oxygen) common features of all respiratory surfaces: thin(so gases can pass through quickly and efficiently), moist(gases can only pass across is they are dissolved in liquid), have a large surface area(so gas exchange occurs quickly enough(fast RATE) to meet metabolic demands of organism) additional feature of respiratory surface of multicellular organisms- blood supply(usually in capillaries) in close contact with the respiratory surface. describe movement of oxygen and carbon dioxide across respiratory surface by diffusion. (each will diffuse from where its molecules are in high concentration to where its molecules are in comparatively low concentration. structure and function of mammalian respiratory system: nose, trachea, bronchi, bronchioles, alveoli(lungs) (especially consider role of the hairs, mucus, ciliated cells, cartilage found in various parts of the system) Be able to recognise structure of respiratory system in a picture Breathing: inhalation and exhalation - especially the role of diaphragm muscle and intercostal muscles Gills: how are they similar and different to lungs? Why don’t we have gills instead of lungs? Transport of oxygen and carbon dioxide around the body, especially the role of haemoglobin and bicarbonate ions. 5 VCE Biology Unit 1: Course Content Excretory system: Location and general function of kidney, ureter, bladder, urethra, urinary sphincter muscle. Role of the excretory system (its importance) Structure and function (simple function only) of the nephron: recognize glomerulus, bowman’s capsule, tubules(proximal convoluted tubule in particular), loop of Henle, collecting duct. Consequence of damage to different parts of the nephron Specialised cells of the kidney tubule and how their structure is suited to their function- in particular the presence of microvilli and no. of mitochondria Composition of filtrate versus composition of urine Composition of blood in glomerulus versus filtrate and urine Significance of different lengths of loop of Henle in terms of concentration of urine that can be produced. (how effectively water can be reabsorbed back into the bloodstream Excretion by plants: No excretory system, few metabolic wastes, mainly storage in tissues that are to be dropped from the plant. Reproduction Asexual reproduction: Cell cycle Mitosis and Interphase (G1, synthesis, G2) Mitosis: process of cell division where by a parent cell produces two daughter cells. These daughter cells are genetically identical to each other and to the parent cell from which they were formed. (The parent cell no longer exists, as its matter has been shared between the daughter cells). A 2n cell produces two 2n cells. Mitosis involves different phases: proprase, metaphase, anaphase, telophase. The order and basic outline of each stage should be known and you should be able to recognize each from a photo or diagram. Chromosomes carry the genetic information: be familiar with their basic anatomy: double stranded chromosome, chromatid, single stranded chromosome, centromere The number of chromosomes present in a “normal” (somatic) body cell is called the DIPLOID number or 2n. Cells of this type have two of each chromosome present. The number of chromosomes present in a gametes such as an egg or sperm(where only one of each chromosome type is present) is called the HAPLOID number or n. Mitosis is the process involved in normal growth and also in asexual reproduction: Asexual reproduction: Reproduction of a new individual from one parent without the fusion of gametes. Offspring are genetically identical to each other and to the parent organism from which they are formed 1. In eukaryotic organisms (organisms whose cells contain a membrane bound nucleus) this process basically involved the process of mitosis. Examples: Vegetative propagation in plants: Cuttings: parts of stems of plants Horizontal stems: Runners: running horizontally over the ground eg. Strawberries Rhizomes: running horizontally under the ground eg. Bracken fern Tubers: swollen end of rhizome (stem tuber) eg. Potato swollen root (root tuber) eg.Dahlia Bulbs: modified stem enclosed by fleshy scale like leaves eg. Onion , garlic Suckers: vertical growth sprout upwards from the root to give rise to new plants- eg. Black berries, poplars Spores: reproductive structures formed through mitosis: ferns 6 VCE Biology Unit 1: Course Content In animals: Regeneration Budding Binary fission Parthenogenesis Artificial asexual reproduction: CLONING 2. In prokaryotic organisms (organisms who cell does not contain a membrane bound nucleus) the cell simply splits into two. E.g Binary Fission Benefits of asexual reproduction: Quick: producing large numbers of offspring over a short time frame Only requires One parent to be present Requires little energy. Good survival rates in a stable environment Problem with asexual reproduction: No genetic diversity. In cases where there in environmental change there is less chance that a suitable variant will be present in the population who is able to survive the change. This could result in a species becoming extinct. (ie. One out all out) Sexual reproduction Involves the fusion of two haploid gametes to form a diploid zygote, and produces genetically unique offspring. These gametes can come from one parent only, or two different parents. Haploid gametes are formed by the process of meiosis. Number of gametes produced is related to the chance of successful fertilization. Number of offspring produced is related to the chance that individual offspring will survive until reproductive age and reproduce. 7