Chapter 4 - Transport Across Cell Membranes Flashcards
What is the basic structure of a cell surface membrane?
- Phospholipid bilayer with hydrophilic heads and hydrophobic tails
- Glycoprotein
- Channel proteins that span the membrane
- Carrier protein that do not span the whole membrane
- Glycolipid
What is the function of cholesterol in a cell surface membrane?
- Binds to hydrophobic tails
- Supports to make more rigid
- Strength and support as no cell wall or other surrounding cells
What are the properties of phospholipids in cell surface membranes?
- Hydrophobic inwards, hydrophilic outwards
- Can slide over each other
- Non polar molecules can diffuse through
Define diffusion
The net movement of molecules from high to low concentration in a passive process
What are the three things that affect diffusion?
- Concentration gradient
- Diffusion distance
- Surface area
Define facilitated diffusion
The passive movement of molecules across a membrane via a specific transmembrane protein from high to low concentration
Summarise the role of a protein channel in facilitated diffusion
- Transports small, polar molecules
- They bind to the channel causing it to change shape and allowing it to pass
Summarise the role of a carrier protein in facilitated diffusion
- Molecules binds to the protein (large)
- Causes it to change shape and release to other side
Why are the structure of proteins important in facilitated diffusion
- Specific tertiary structure
- Complementary to the molecule it transports
Summarise the process of active transport
- Against a concentration gradient
- Use of ATP via a carrier protein
Summarise co-transport
- Via a carrier protein
- Moves 2 molecules at one
- One goes down and one goes against the gradient
Summarise how glucose is absorbed into the blood of the ileum
- Sodium is actively transported by Na/K carrier protein into blood
- Lowers concentration gradient in cell and creates a gradient
- Sodium moves into cell by facilitated diffusion and brings a glucose molecule against the gradient
- Glucose then diffuses into the blood by facilitated diffusion
Define osmosis
The passive movement of water molecules from a high to low water potential across a partially permeable membrane
What does a high water potential have?
- High % of water
- Low % of solute
- Low solute conc
- Hypotinic
What does a low water potential have?
- Low % of water
- High % of solute
- High solute con
- Hypertonic
