Cell Membrane (PPT 5-7) [U1/ T1] Flashcards
What is the structure of the cell membrane?
- Double layer of phospholipids
- Embedded proteins in phospholipid layer
- Contains glycoproteins, glycolipids & cholesterol
Explain why the structure of the cell membrane is considered a fluid mosaic model?
- Fluid because the components can move
- Mosaic because the proteins embedded create a mosaic look.
What is the structure and function of Integral proteins?
S- Span both phospholipid layers generally
F- Cell to cell communication,
- Joining of cells
- Anchorage
- Enzymes
What is the structure and function of Peripheral proteins?
S- Stacked on the inside of outside of the membrane
F- Cellular communication
- Assist with structure & shape of the cell
What is the structure and function of Glycoproteins?
S- Short chain
- Carbohydrates attached to proteins & lipids on the extracellular side of membrane.
F- Act as antennae
- Recieves chemical messesges
- Marks and identifies.
What is the structure and function of Glycolipids?
S- Short chain
- Carbohydrates attached to proteins & lipids on the extracellular side of membrane.
F- Act as antennae
- Recieves chemical messesges
- Marks and identifies.
What is the structure and function of Cholesterol
S- Found within phospholipid layers
F- Provide stability, but do not affect fluidity
- Increases flexibility & rigidity of membrane
- Assists with changing temperatures
What is diffusion? Is it active or passive? Where does diffusion occur?
The net movement of substances from an area of high concentration to a low concentration
- No energy required = Passive
- Driven by concentration gradient
- Occurs across the membrane.
What is facilitated diffusion? Is it active or passive? Where does facilitated diffusion occur?
Diffusion of ions and larger polar molecules via the concentration gradient, but aided by protein channels are carriers as they cannot pass the lipid bilayer
- No energy required - passive
- Driven by concentration gradient, faster than diffusion
- Occurs through protein channels and protein carriers
What is osmosis? Is it active or passive? Where does osmosis occur?
Net diffusion of water across a partially permeable membrane from a region of higher to lower concentration of water molecules.
- Occurs from dilute to concentrated solution
- The pressure causing the water to move is called osmotic pressure.
Define these terms relating to osmosis?
1) Isotonic
2) Hypertonic
3) Hypotonic
1) Isotonic = No net movement, water concentration is the same.
2) Hypertonic = Higher concentration of solute, water will leave the cell.
3) Hypotonic = Lower concentration of solute, water will enter the cell
What are four factors that affect the rate of diffusion?
1) The concentration gradient
2) Diffusion distance
3) Surface area
4) Any physical barriers
Why is the size of a cell limited by the surface area to volume ratio?
Because as the cells size increases, the surface area decreases, this compromises the diffusion.
To thrive, cells must be small with a large SA/V ratio.
What is active transport?
The movement of dissolved molecules in or out of the cell membrane. Energy is required as substances are moved against the concentration gradient.
What is endocytosis?
The movement of materials from outside to inside the cell via a membrane bound vesicle or vacuole.
