Transport Across Cell Membrane Flashcards
What is a Phospholipid?
Similar to lipids but have a phosphate group instead of one fatty acid.
Phosphate = hydrophilic
Fatty acid=hydrophobic
Whats the reason for a Phospholipid to have one hydrophilic end and one hydrophobic end?
Allows them to form a bi layer membrane with the phosphate pointed out
What is the Fluid Mosaic Model?
A model used to demonstrate that the Phospholipid bilayer moves like a fluid
Describe a Fluid Mosaic Model?
Hydrophilic and hydrophobic Phospholipid
Channel proteins
Receptor proteins
Cholesterol
Cytoskeleton
Glycoprotein
Glycolipids
Function of chloroplasts in Phospholipid Bilayer?
Regulate fluidity and permeability of the cell membrane to prevent phospholipids to stiffen
Increases strength of cell surface membrane
Define Diffusion?
Net movement of molecules or ions from a region from high conc to a low conc until evenly distributed
What is simple diffusion?
Normal diffusion involving limitations of the Phospholipid bilayer
What is Faciliated Diffusion?
Diffusion involving the roles of carrier proteins and channel proteins
Large,ionic or polar molecules require facilitated diffusion
Why does Faciliated Diffusion platoe on a Rate of Uptake/concentration graph?
Channel proteins decrease rate of uptake when the concentration of carrier proteins exceed no of Channel proteins
This means carrier proteins are saturated and used up
What is a channel protein?
Allows water soluble ions/molecules to diffuse through
Contains hydrophobic amino acids
What is a carrier protein?
A protein that can change shape to transfer molecules or ions from one side of the membrane to another
Factors affecting the rate of diffusion?
Concentration gradient
Particle size/charge
Temperature
Surface Area
Distance
Channel/carrier proteins
Function of Phospholipid Bilayer?
Forms a barrier to water/charged molecules and allows non polar substances though
What substances does Facilated diffusion allow?
Allows polar and charged molecules such as carbohydrates,amino acids and ions
What is osmosis
Faciliated Diffusion of water through aquaporins which go through a semi permeable membrane
From a high water potential to a low water potential
Why does faciliated diffusion increase permeability?
FD requires use of channel proteins which increase permeability
How do carrier proteins change shape?
Binding of substance to protein and hydrolysis of ATP cause carrier proteins to change shape
What is active transport?
Movement of molecules/ions from a low to high conc,against the conc gradient which requires ATP from aerobic respiration
And is an active process
What is the Sodium potassium pump?
An important example of AT,which is a cycle of removing 3 sodium ions and allowing 2 potassium ions to enter creating an electric gradient of 1-
What is ATPase and what’s the function?
ATPase is an enzyme involved in catalysing hydrolysis of ATP so potassium can enter the cell and sodium can be released
Process of Sodium Potassium Pump?(6 long steps)
Cytoplasmic Na+ binds to sodium potassium pump(channel protein)
Na+ binding stimulates phosphorylation(A phosphate from ATP attaches to CP)
Phosphorylation causes protein to change conformation,expelling 3 Na+
K+ binds to inside of CP triggering release of phosphate
Loss of phosphate restores proteins original conformation
2 K+ ions is released in cell
What’s phosphorylation?
ATP loses on phosphate and attaches to protein channel
3 locations of The Potassium/Sodium Pump and function?
Large intestine-When sodium ions move back in cell,intestine absorbs phosphate and glucose
Nerve cells-so there is an electric gradient
Kidney-helps maintain osmotic equilibrium and membrane potential in cells and stabilises membrane potential regulating cell volume
What is Co Transport?
Absorption of Sodium ions and glucose by cells in the ileum involving active transport and FD
