VCE Unit 1 Biology

1. VCE Unit 1 Biology Revision Notes

2. This unit of study has explored the following ideas: • cell structure • cell functioning • composition of cells • internal and external environments of cells • cell replication • common requirements of living things • reproduction Key Knowledge

3. The Cell Theory states that: • All organisms are made up of cells and/or the products of cells • All cells are derived from pre-existing cells • The cell is the smallest organisational unit of a living thing • Prokaryotic cells are relatively small and primitive. They lack membrane bound organelles. The DNA is free floating in the cytoplasm. Bacteria and cyanobacteria are prokaryotic. • Eukaryotic cells are relatively larger and more complex, containing membrane bound organelles including a nucleus. Protists, Fungi, Plants and Animals are all eukaryotic. Cell Structure

4. Cell Organelles • Nucleus – Controls cell activities • Mitochondrion – site of aerobic stages of cellular respiration • Ribosomes – site of protein synthesis • Endoplasmic reticulum – protein synthesis and transport within the cell • Golgi Body – packaging of substances in preparation for secretion from cell • Chloroplast – site of photosynthesis • Lysosomes – produce digestive enzymes within cells • Vacuoles – storage sacs for dissolved substances • Cell Wall – contributes to structural support of the plant • Plasma Membrane – partially permeable, flexible barrier controlling what comes in and goes out of the cell Cell Functioning

5. Photosynthesis • This process occurs in the chloroplasts of plant cells as they contain the pigment chlorophyll • Converts inorganic substances and light energy into the organic energy store – glucose. • This is an endergonic process requiring a net input of energy (Anabolic) 6CO2 + 12H2O  C6H12O6 + 6O2 + 6H20 • Cellular Respiration • This process occurs in the cytosol and mitochondria of all living things • Glycolysis – occurs anaerobically in the cytosol releasing 2 ATP • Krebs Cycle – occurs within the mitochondria releasing 2 ATP • Electron Transfer – occurs within the mitochondria releasing 32 – 34 ATP • This is an exergonic process requiring a net output of energy (Catabolic) C6H12O6 + 6O2  6CO2 + 6H20 + 36 – 38 units of ATP Cell Functioning

6. Enzymes • Proteins made by the cell to act as biological catalysts • Enzymes are specific binding with the active sites of specific substrates • Enzyme activity is affected by temperature – at low temperature the enzyme is slow or dormant and at high temperature the active site changes shape and is said to be denatured. • Enzyme activity is also affected by pH. Each enzyme has a particular range of pH in which it works, above or below that the enzyme becomes denatured. Cell Functioning

7. Chemical Components • Carbohydrates – organic compounds made up of C, H, O, N providing an energy source for cells. • Proteins – organic compounds made up of C, H, O, N provide energy when consumed, structures • Lipids – organic compounds made up of C, H, O provide energy, used for energy storage, insulations, structure of membranes • Nucleic Acids – organic compounds made up of C, H, O, N, P contains the genetic code and involved in protein synthesis • Water – inorganic, all chemical reactions in organisms take place in solution • Minerals – inorganic – includes N, P, Fe, Mg – used in making organic compounds, components of haemoglobin and chlorophyll etc. • Vitamins – organic compounds, Vit C, Vit D for example operating as coenzymes Composition of Cells

8. Plasma Membranes • Diffusion • Diffusion is the movement of molecules of a substance from an area of high concentration of that substance to an area of low concentration • Osmosis • Osmosis is the movement of water from an area of low concentration of a dissolved substance to an area of high concentration of that dissolved substance. • Facilitated Diffusion. • For non-lipid soluble chemicals, such as glucose, diffusion occurs through the protein channel. • Active Transport. • For chemicals that need to be moved against a concentration gradient it is required to use energy to move such chemicals through the protein channel. • Surface Area to Volume Ratio • When substances enter or leave cells, the rate at which they move is determined by a number of factors: concentration, temperature and the SA:V – the more SA for a particular V increases the speed of movement across the membrane, Internal and External Environments of Cells

9. Purposes of cell replication • Maintenance – replace old or damaged cells • Growth – parts of or whole organisms • Cell Cycle • Interphase • G1 – pre DNA synthesis • Synthesis – the chromosomes are copied • G2 – post DNA synthesis • Mitosis • Prophase – chromosomes uncoil becoming visible and the nuclear membrane dissolves • Metaphase – chromosomes line up along the equator of the cell attaching to spindle fibres • Anaphase – spindle fibres contract, causing centromeres to split and the sister chromatids to move to the poles of the cell • Telophase – a new nuclear membrane forms and the chromosomes recoil and become indistinct. • Cytokinesis – the cell divides into two cells diving the cell contents reasonably equitably Cell Replication

10. All living things are composed of cells and therefore need to: • obtain nutrients and energy • process nutrients • distribute materials • remove wastes • exchange gases • reproduce Common Requirements of Living Things

11. Autotrophs are capable of making their own organic compounds from inorganic substances. • Plants require carbon dioxide (gained via gas exchange), water, nitrogen, sulfur, magnesium, potassium, calcium and phosphorus for healthy growth (which are gained from the soil) • To gain energy plants create glucose in photosynthesis. This occurs in two stages: • Light dependent – occurs in the grana, red and blue light absorbed and energy is used to break water molecules • Light Independent – occurs in the stroma glucose is formed Nutrition - Autotrophs

12. Heterotrophs also require energy and a range of macro and micro nutrients. However, heterotrophs are unable to create these for themselves and must consume other organisms. • This requires a digestive system: • Mouth and teeth • Oesophagus • Stomach • Small intestine • Large intestine • Rectum • Anus • Pancreas • Liver and Bile Duct • Herbivores, Carnivores & Omnivores Nutrition - Heterotrophs

13. In simple single celled organisms and small multicellular organisms distribution is achieved via diffusion. • In larger organisms systems are required to move materials around the organism. • Animals – blood, heart, arteries, arterioles, capillaries, veinules and veins. • Plants – phloem and xylem Circulation

14. In animals, respiratory surfaces need to have: • large surface area • Thin, moist and easily penetrable surface • Adequate ventilation • Efficient transport of blood to the respiratory surface • Animals need to release carbon dioxide as waste and take in oxygen. • Plants also need to exchange gases, but generally require carbon dioxide to enter and release water vapour and oxygen. • Plants control gas exchange by the opening and closing of stomata Gas Exchange

15. In animals, the waste products of cellular respiration must be excreted. • Nitrogenous wastes take the form of ammonia, urea and uric acid • The organ responsible is the kidney. • In plants, there are no specialised organs as plants produce less waste and reuse some of the waste products Waste Removal

16. Reproduction of organisms can occur via asexual or sexual means. • Asexual • Occurs in single celled and simple organisms and simple plants and animals • All new individuals are identical to parents • Does not require a mate • Lack of genetic variety • Sexual • Genetically unique individuals are formed • Fusion of haploid gametes to produce diploid zygote • Requires a male and a female • External fertilisation • Internal fertilisation Reproduction