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VCE Unit 1 Biology. Revision Notes. 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. - PowerPoint PPT Presentation
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Revision Notes
VCE Unit 1 Biology
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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