Plasma membranes Flashcards
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- All living organisms are composed of one or more cells
- Cells are the basic functional unit of life
- All new cells arise from pre-existing cells
Whats the characteristics of the phospholipid bilayer
- Hydrophilic (polar) head faces out because surrounding this contraption is water
- Hydrophobic (non-polar) tails face each other so that only small and hydrophobic molecules an pass through.
Why is the plasma membrane considered semi-permeable?
It allows the passage of some substances but not others
Use of protein channels
Provide an alternative pathway of entry or exit for ions
Use of protein carriers
Provide an alternative pathway of entry or exit for Large molecules.
Protein carriers process
Protein carriers ‘carry’ the molecule from one side of the cell to the other. Once the molecule binds. the protein changes its shape. pulling the molecule from one side of the cell to the other.
Describe glycoprotein
Are proteins with carbohydrate rings bonded to them. Often acting as a receptor for signalling molecules.
Describe glycolipids
Are lipids with carbohydrate rings bonded to them
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- Maintain the fluidity of plasma membrane by acting as a barrier between the two flanking phospholipid molecule
- Maintains stability of plasma membrane prevents the membrane from disintegrating by phospholipid molecules randomly flying off the membrane by binding two phospholipid molecules together, acting as ‘glue’
Movement of substances
- Define passive transport
- Define active transport
- Requires no energy, moving to an area with a high concentration to a low concentration
- Is energy dependent movement of substances against the concentration gradient
Movement of substances
- Diffusion
- Simple diffusion
- Facilitated diffusion
- The net movement of a substance from a region of high concentration to a region of low concentration
- is the process by which solutes are moved along a concentration gradient in a solution or across a semipermeable membrane. If the molecules are small enough, this simple diffusion can happen across cell membranes, between the individual phospholipids that make up the membrane.
- Is the net movement of a substance through a plasma membrane via protein channels or protein carriers (no energy)
Movement of substances
-Define Endocytosis
Is the process involving the entry of substances into the cell by the formation of a vesicle from the plasma membrane
Movement of substances
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- Phagocytosis- large marcomolecules or who structures are endocytosed
- Pinocytosis- fluid with only small dissolved molecules in endocytosed
- Receptor-mediated endocytosis
Movement of substances
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- Protein is synthesised in the ribosome within the rough endoplasmic reticlulm (ER) by the process of translation
- The protein is transported along the membrane of the rough ER and is modified throughout the process
- The protein is transported via a vesicle to the golgi apparatus, where it is modified and packaged into another vesicle
Movement of substances
Define osmosis
Osmosis is the spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.
