2.3 Transport Across Cell Membranes Flashcards
What model do all membranes have
Fluid-mosaic
What are the major components to the cell membrane
- Phospholipid Bilayer
- Channel Protein
- Carrier Protein
- Glycoprotein
- Glycolipid
- Cholesterol
Name the component of the cell membrane
Phospholipid Bilayer
Name the component of the cell membrane
Channel Protein
Name the component of the cell membrane
Glycoprotein
Name the component of the cell membrane
Carrier Protein
Name the component of the cell membrane
Glycolipid
Name the component of the cell membrane
Cholesterol
Describe the arrangement of phospholipid molecules in the phospholipid bilayer
- Two layers of phospholipids
Hydrophilic heads face outside - Hydrophobic tails face inside
Describe and explain the advantages of the phospholipid bilayer in the cell membrane
- Selectively-permeable barrier
- Only non-polar molecules are able to pass through via simple diffusion
- Bilayer is fluid
- Can bend to take up different shapes, forming vesicles
Describe and explain the advantages of channel proteins in the cell membrane
- Protein through bilayers
- Allows water soluble substances through via faccilitated diffusion
Describe and explain the advantages of carrier proteins in the cell membrane
- Protein through bilayer
- Allows substances to move through via faccilitated diffusion and active transport
Describe and explain the advantages of glycoproteins in the cell membrane
- Protein with short carbohydrate chain
- Cell recognition and signalling
- Cell attachment
Describe and explain the advantages of glycolipids in the cell membrane
- Phospholipid with short carbohydrate chain
- Cell recognition and signalling
- Cell attachment
Describe and explain the advantages of cholesterol in the cell membrane
Regulates membrane fluidity
Simple diffusion: Movement of molecules
- Along concentration gradient
- From higher concentration to lower concentration
Simple diffusion: Active or passive
- Passive
- No ATP hydrolysed
Simple diffusion: Movement through what
Diffuse through phospholipid bilayer
Simple diffusion: Type of molecule
Non-polar
Faccilitated diffusion: Movement of molecules
- Along concentration gradient
- From higher concentration to lower concentration
Faccilitated diffusion: Active or passive
- Passive
- No ATP hydrolysed
Faccilitated diffusion: Movement through what
Channel and carrier proteins
Faccilitated diffusion: Type of molecule
Polar / Charged
Osmosis: Movement of molecules
- Movement of water along a water potential gradient
- From an area of high water potential
- To an area of low water potential
Osmosis: Movement of molecules regarding solute concentration
Low to high solute concentration
Osmosis: Passive or active
- Passive
- No ATP hydrolysed
Osmosis: Movement through what
Water channel proteins (aquaporins)
Water IN by osmosis : Cell apperance
Turgid
Water IN by osmosis : Cytoplasm
Hasn’t shrunk from cell wall
Water IN by osmosis : Cell in what solution
Hypotonic
Water IN by osmosis : Water potential of cell and solution
Solution has higher water potential than cell
Water IN by osmosis : Net movement of water
Into the cell by osmosis
Water OUT by osmosis : Cell appearance
Plasmolysed
Water OUT by osmosis : Cytoplasm
Shrunk from cell wall
Water OUT by osmosis : Cell in what solution
Hypertonic
Water OUT by osmosis : Water potential of cell and solution
Solution has a lower water potential than the cell
Water OUT by osmosis : Net movement of water
Out of the cell, by osmosis
Water potential of pure water
0kPa
Water potential of a solution more concentrated than pure water
Less than 0kPa
Relationship between water potential and solute concentration
More concentrated solute = lower water potential
Active Transport: Movement of molecules
- Against concentration gradient
- From lower concentration to higher concentration
Active Transport: Active or passive
- Active
- Requires ATP hydrolysis
Active Transport: Movement through what (+description)
- Carrier protein
- Protein changes shape, as substrate binds
What occurs when a substrate binds to a carrier protein
Protein changes shape
Describe exocytosis
Fusion of a vesicle with the cell-surface membrane
Describe endocytosis
Engulfment of molecules by cell-surface membrane to form vesicles
State the ways in which cells adapt to increase the rate of transport across a membrane
- Increased number of channel and carrier proteins
- Folded membrane
- Increased number of mitochondria
Describe how increasing the number of channel/carrier proteins increases the rate of transport across a membrane
More faccilitated diffusion / active transport
Describe how a folded membrane increases the rate of transport across a membrane
Increases surface area
Describe how an increased number of mitochondria increases the rate of transport across a membrane
Supply more ATP for active transport