b2.1 (ai generated notes) Flashcards
What is simple diffusion based on?
The size and hydrophobic/hydrophilic nature of molecules.
What do channel proteins do?
Facilitate movement down a concentration gradient.
What is active transport?
The movement of molecules against a concentration gradient using energy.
Define Osmosis.
The diffusion of water across a selectively permeable membrane from a solution of higher concentration to a lower concentration.
How is osmosis different from diffusion?
Osmosis only occurs across a membrane and involves the diffusion of water.
What type of substances are membranes impermeable to during osmosis?
Large polar substances.
What creates the regions of different solute concentrations across a membrane?
The impermeability of membranes to large polar substances.
Outline the structure of aquaporins.
Integral proteins composed of 4 monomeric subunits, each with a water channel lined with hydrophilic side chains.
What is the function of aquaporins?
Allow water to flow through the membrane while preventing ions.
Why are the channels within aquaporins hydrophilic?
To allow water to pass through the hydrophobic lipid bilayer.
How does facilitated diffusion differ from simple diffusion?
Facilitated diffusion requires carrier/channel proteins for solute movement.
What is the difference between passive and active transport?
Passive transport requires no energy and moves substances from high to low concentration; active transport requires energy and moves substances from low to high concentration.
Define active transport.
The movement of molecules against a concentration gradient, requiring energy from ATP.
What is direct active transport?
Transport where energy is released by an exergonic reaction to move molecules across membranes.
What is indirect active transport?
Movement of one solute down its concentration gradient driving the movement of a second solute against its gradient.
Give examples of when active transport is used.
- Uptake of glucose
- Removal of waste materials
- Maintenance of ion concentrations in cells
- Uptake of mineral ions in roots.
What additional components do most membranes contain?
Carbohydrates, in addition to phospholipids and proteins.
What are glycolipids?
Carbohydrates covalently bound to lipids in the cell membrane.
What are the two classifications of glycolipids?
- Glycoglycerolipids
- Glycosphingolipids.
What is the glycocalyx?
The sticky layer formed by carbohydrate groups of glycolipids and glycoproteins that protrude from the cell surface.
What role does the glycocalyx play?
IT IS THE LAYER OR GLYCOPROTEINS ANFD GLYCOLIPIDS
*
* * Cell signaling
* Cell adhesion
* Cell-cell recognition
* Protection of the cell surface.
What does the Fluid Mosaic Model state about the lipid bilayer?
It is fluid, and its fluidity depends on the nature of fatty acids and cholesterol.
What do integral and peripheral proteins contribute to?
The mosaic nature of the lipid bilayer.
Where are carbohydrates located in the membrane?
On the extracellular side of the membrane, playing a role in cell recognition.
