Cell Transport Flashcards
(34 cards)
What are the functions of membranes?
Separate organelles so specific metabolic functions can happen
Concentration gradients form
Control entry + exit of material
Isolate enzymes
Surfaces for reaction
What do phospholipids form when submerged in water?
Micelles
Describe the structure of a phospholipid
Hydrophilic head face outwards
Hydrophobic tail face inwards
Bilayer formed
Describe the function of phospholipids
Separates contents of organelles
Barrier to larger/polar molecules + ions
Allow soluble lipids to enter/exit
Membrane = flexible + self sealing
What types of proteins are in a cell membrane? Where are they in the membrane?
Extrinsic = spans part
Intrinsic = spans entire
What are the two types on intrinsic proteins? What do they do?
Channel and carrier proteins
Transport substances across membrane
What are channel proteins?
Water filled tubes that allow water soluble ions to diffuse across membrane
What are carrier proteins?
They bind ions or molecules (eg glucose/amino acids) + change shape in order to transport them across membrane
Describe the structure of glycoproteins
Proteins with carbohydrates attached that stick out the surface
What is the function of glycoproteins?
Act as cell receptors for hormones/neurotransmitters
Act as recognition sites (antigens) -> lymphocytes can recognise own cells
Help form tissues
Describe the structure of glycolipids
Phospholipid with carbohydrate chain covalently bonded -> sticks out from surface
What is the function of glycolipids?
Sites for cell signalling (act as hormone receptors)
Act as antigens
Hold together to form tissues
Where is cholesterol found in the cell membrane?
Within bilayer between phospholipids and proteins
What does cholesterol in the cell membrane do?
Adds strength -> reduces lateral movement (decreases fluidity at high temps)
Prevents water + dissolved ion leakage (hydrophobic)
What can travel straight through the bilayer?
Small, soluble lipids
What factors affect membrane fluidity?
Temperature
Solvents
What is diffusion?
The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
What is facilitated diffusion?
A passive process that uses carrier or channel proteins to facilitate movement of larger molecules or charged particles.
What happens to carrier and channel proteins in facilitated diffusion?
Carrier: change shape
Channel: form pores specific to particle
What factors affect facilitated diffusion?
Concentration gradient
Number of carrier and channel proteins
What is active transport?
The net movement of molecules or ions from an area of low concentration to an area of high concentration using ATP and carrier proteins.
Why is active transport an active process?
Carrier proteins need ATP to change shape.
ATP-> ADP + phosphate molecule (hydrolysed) - releases energy
What is endocytosis?
Moves particles into cell by enclosing them in a vesicle made of plasma membrane
Membrane invaginates to form pocket
Pocket pinches off with help of specialised proteins
What is exocytosis?
How cell transport signals chemical or waste products from inside to outside cell in vesicles which fuse with plasma membrane.
