the panda is black and white, like a bear in shape, but different. Things to remember in the last hour before the exam: Life processes at the cellular level (This is not a revision sheet – you’ve done that by now - it’s a list of things you might want to remind yourself about …)
1. Cell parts. Most structures/organelles common to animal and plant cells. [P] = plants only Cytoplasm – transparent jelly – cells activities occur here Cell/plasma membrane – regulates movement of materials in/out of cell. SELECTIVELY permeable. Phospholipid bilayer. Phosphate heads (hydrophilic) face inside cell/outside cell. Fatty acid tails of lipids (hydrophobic) to interior. Small molecules e.g. water diffuse through. Larger ones transported via protein channels.
Nucleus – cell “control centre”, controls metabolism via enzymes. Contains genetic info - DNA. Chromosomes only visible when cell is dividing. Contains nucleolus – makes RNA and ribosomes. Cell wall [P] – protects cell – gives strength and support. Is permeable and made of cellulose. Controls turgidity (can resist high internal pressures without stretching). Chloroplasts [P] – site of photosynthesis, contain chlorophyll - green light-trapping pigment. Elongated shape maximises S.A. to volume ratio, increasing uptake of CO2 and H2O uptake and output of O2 and glucose (photosynthetic capacity). Chlorophyll molecules embedded in grana (stacks of thylakoid membrane) – more S.A. = more chlorophyll = max. amount of light captured = more photosynthesis. Surrounded by stroma – enzymes and water.
Large (central) vacuole [P] – large and permanent structure containing cell sap (salts, sugars, & amino acids). Salts in sap produce strong tendency for water to enter cell (by osmosis) keeping cell turgid. Vacuole displaces cytoplasm to edges of cell – meaning chloroplasts are close to CO2 and light. Also short gas diffusion distances.
Mitochondria – site of aerobic respiration. Enzymes attached to cristae (membranes...
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