Level 2 NCEA Cell Structure

Cells Structure
1. Cell membrane
  1. separates cell & environment
  2. 2 layers of lipid molecules (phospholipid bilayer)
    1. bilayer is fluid -> allows proteins to move
  3. controls entry/exit of substances in & out of the cell
  4. semi-permeable- allows passage of only certain substances
    1. oxygen, carbon dioxide, glucose, freely diffuse
2. cytoplasm
  1. jelly_like fluid
    1. water, ions in solution, small molecules & proteins
  2. where most of chemical reactions occure
  3. supports organelles
3. nucleus
  1. largest organelle in cell- double membrane
    1. membrane connected to ER
  2. many large pores- pass of materials in and out
  3. contains genetic material
  4. controls cell activities and processes
4. Mitochondria
  1. oval shape- increases S.A: Vol ratio
    1. so more oxygen can diffuse into mitochondria faster
  2. found in large numbers in cells that need a lot of E
    1. e.g. sperm, muscle, liver
      1. cells lining kidney tubules- very active- reabsorb substances by active transport
  3. inner membrane forms folds: cristae
    1. increases surface area for enzymes to work on
  4. aerobic respiration
  5. outer membrane controls exit/entry of materials
  6. matrix: fluid filled space inside mitochondria
5. Endoplasmic Reticulum
  1. network of membranes running through cytoplasm
  2. rough endoplasmic reticulum
    1. ribosomes attached- protein production
    2. common in cells that make and secrete proteins
      1. e.g. digestive cells to produce enzymes
  3. smooth endoplasmic reticulum
    1. production of lipids
    2. common in cells that produce steroid/hormones
      1. e.g. oestrogen, progesterone, testosterone
  4. functions as a transport system
    1. carries materials within cell from nucleus -> outside of the cell
6. ribosomes
  1. site of protein synthesis
  2. made in nucleus
  3. attached to ER
    1. making proteins for use inside the cell
  4. free in cytoplasm
    1. proteins for outside the cell
      1. secreted or used in cell membrane
  5. made of 2 subunits to form the protein-synthesising unit
7. Golgi body
  1. consists of stack of membrane sacs- cisternae
  2. after being synthesised most molecules pass through golgi body
  3. transports and stores lipids from ER
  4. modifies chemicals transported to it from ER and secretes
8. vacuoles
  1. fluid filled spaces surrounded by a membrane
  2. storage
    1. toxic substances- later excreted from cells
    2. water, sugars, proteins, salts
    3. animal cells- food vacuoles
    4. organic compounds, amino acids, inorganic ions
    5. pigments
      1. e.g. for petals
9. Lysosomes
  1. small vacuoles containing digestive enzymes
    1. membrane prevents enzymes from digesting cells itself
  2. releases enzymes
    1. digest/destroy worn-out organelles within the cell
    2. digest material taken into the cell
    3. e.g. break down ovum membrane to allow sperm head entry
10. PLANT CELLS ONLY
  1. Cell wall
    1. made of many tiny cellulose fibres made of thousands of cellulose molecules
    2. fibres at right angles
      1. provide strength
    3. provides support to the cell
      1. allows it to be turgid without bursting
  2. Chloroplasts
    1. found in photosynthetic cells
      1. plant leaves and stems
    2. site of photosynthesis
    3. contains grana
      1. grana=piles of flattened membranes called thylakoids
      2. contains chlorophyll
        chlorophyll converts light E -> ATP
      3. have increased surface area for light absorption
        increases rate of photosynthesis
    4. fluid=stroma
      1. contains enzymes involved in final stages of photosynthesis
      2. have large starch granules
        form a temporary store for products of photo synthesis
11. cilia and flagella
  1. cilia
    1. hair like short found in large numbers
    2. create currents
      1. move chemicals about/over suface of cell
        e.g. in the trachea
      2. move the cell
  2. projecting from surface of some animal/plant cells
  3. flagella
    1. whip-like 'tails'
    2. usually singular
    3. move the cell
      1. e.g. sperm

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Level 2 NCEA Cell Structure

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