Plant cell structure (2)

Chloroplasts
1. Structure
  1. Chloroplast envolope
    1. Double plasma membrane that surrounds the organelle
    2. Highly selective with what it allows to enter and leave the chloroplast
  2. Grana
    1. Stacks of up to 100 disc-like structures called thylakoids
    2. Within the tylakoids is the photosynthetic pigment chlorophyll
    3. Some tylakoids have tubular etensions that join with thylakoids in adjacent grana
      1. Intergranal lamella
    4. Where the first stage of photosynthesis takes place
  3. Stroma
    1. Fluid filled matrix where the second stage of photosynthesis takes place
    2. Contains a number of other structures such as starch grains
2. Relationship to function
  1. Function is to harvest sunlight and carry out photosynthesis
  2. Granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes which carry out the 1st stage of photosynthesis. These chemicals are attached to the membrane in a highly ordered fashion
  3. Fluid of stroma possesses all the enzymes needed to carry out stage 2 of photosynthesis
  4. Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture proteins needed for photosynthesis
Cell wall
1. Structure
  1. Consist of a number of polysaccharides, such as cellulose
  2. Cell wall consists of microfibrils of the polysaccharide cellulose embedded in a matrix
  3. Thin layer called the middle lamella, which marks the boundary between adjacent cell walls and cements adjacent cells together
  4. 3 layers - middle lamella, primary wall and secondary wall
  5. Microfibrils are small fibres made of glycoproteins and cellulose
2. Functions
  1. To provide mechanical stength in order to prevent cell birsting under turgor pressure
  2. Mechanical strength for the plant as a whole
  3. To allow water to pass along it and so to contribute to the movement of water through the plant
  4. Cellulose microfibrils have considerable strength, allowing the cell wall to carry out its functions
Plasmodesmata
1. Function
  1. Allows neighbouring cells to link together
2. Structure
  1. Gaps in cell walls
  2. 3 main layers
    1. Cell membrane
    2. Cytoplasmic sleeve
      1. Fluid filled space through which things can be transported
    3. Desmotubule
      1. Channel of appressed ER between neighbouring cells
3. Relationship
  1. The gap allows materials to be shared
Vacuole
1. Function
  1. Creates turgor pressure for support
  2. Storage
2. Structure
  1. Fluid filled sac containing cell sap
    1. Water, amino acids, glucose, salts
  2. Tonoplast membrane
    1. Separates vacuole contents from the rest of the cell
    2. Regulates movement in and out of the vacuole
3. Types
  1. Food
    1. Stores and digests ingested food
  2. Contractile
    1. Pumps out excess water to maintain homeostasis
4. Relationship
  1. Partially permeable tonoplast membrane allows movement in and out and maintains pH and ionic concentration
  2. Enzymes capable of digesting the cell held within, which can be used for programmed cell death (apoptosis)
Root hair cells
1. Absorb water through osmosis
2. Mineral absorbtion through active transport
3. Large surface area
4. Contains carrier proteins in cell membrane for active transport

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Plant cell structure (2)

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	Created by Beth Ritchie over 10 years ago