Cell Structure in Relation to Function

Variation exists between cells of one type of tissue and between cells of different types of tissue. When cells are examined closely structures called organelles become visible.

Red Blood Cells are disk shaped with pores on either side to increase surface area to allow oxygen absorption from breathed-in air which is distributed to the cell. Xylem Cells are dead thickened with lignin, with no end walls or contents so that they can transport water and minerals to support the plant. Phloem cells have end wall pores allowing cytoplasm to connect, this allows the transport of products of photosynthesis. The root hair has a long extension to increase surface area maximising water and mineral absorption to the cell. The Skeletal muscle contains many mitochondria to provide ATP for muscle contraction to assist movement.

Uni cellular organisms have only one cell and contain the organelles they need to survive. Euglena is an example of a unicellular organism. It has a light detector, A flagellum for movement towards light and a chloroplast to carry out photosynthesis.

Plasma Membrane

Animal cells have plasma membrane, plant cells have plasma membrane and cell wall Plasma membrane is composed of protein and phospholipid in a fluid mosaic Phospholipid molecules form a double layer, one set is hydrophobic(repels water), the other is hydrophilic(attracted to water), which allows tiny molecules like water to pass through rapidly Large molecules like glucose have to pass through protein channel for exit or entry to cell Is semi- permeable

Cell Wall

Cell wall is composed mainly of cellulose Consists of chains of glucose molecules grouped together as fibres, tightly packed to make cell strong Adjoining cell walls and inter-cellular spaces provide a water-conducting pathway throughout plant cell wall takes in too much water, prevent further water uptake by making it self turgid Cell wall's function is to provide structure to the cell Is fully permeable

Transport

Diffusion is movement of small soluble molecules from high to lower concentration Osmosis is a type of Diffusion. Movement of water molecules high to low, through selectively permeable membrane Active transport is movement of molecules or ions from low to high concentration, molecules pass through membrane through protein channels and carriers in the membrane. Cell has to produce lots of energy (can be supplied by ATP). Must be respiring aerobically to produce enough ATP for active transport Bulk transport large particles into or out of the cell due to substantial movement of the plasma membrane. In exocytosis cytoplasmic vesicle created within the cell moves to the plasma membrane and fuses with it.

Hypertonic- Having a greater solute concentration than that which it is being compared with.Hypotonic- Having a lower solute concentration than that which it is being compared with.Isotonic- Having the same solute concentration to that its being compared with.

Cell Variety

Absorption and secretion of materials