Unit 1.3 Flashcards
Describe Phospholipids in a membrane in terms of structure
Hydrophillic head + Hydrophobic 3 fatty acid tails
what is the arrangement of Phospholipids?
They form a bilayer with the molecule opposite each other
The hydrophillic heads point outwards + the fatty acids point inwards
The phospholipid component allows lipid soluble molecules to cross but not water soluble
Examples of water soluble?
Na+
K+
Cl-
Po4 3-
Examples of lipid soluble?
O2
Vitamin A
Vitamin K
CO2
Describe proteins in the membrane?
vary in shape size and patern
Extrinsic?
on either surface of the bilayer but does not penetrate through the layer
what is the function of an extrinsic protein?
structural support collectively
Individually?
recongnition site for hormone attatchment
Intrinsic?
extend across both layers of the bilayer
Function?
to transport water soluble substances
if channel, allows the active transport of ions
When was the Fluid Mosaic Model invented and by who?
Singer and Nicolson
1972
What do we say about it?
fats move with respect to each other
vary in shape size and pattern
What is the glycocalyx?
a layer of carbohydrate around the membrane which contains hormone receptors or allows cell - cell recognition
What is diffusion?
the passive movement of molecules or ions down a concentration gradient from a region of high concentration to a region of low concentration
Factors affecting diffusion rate?
surface area of the membrane
nature of the diffusion molecule
(fat soluble = faster than water soluble)
non polar = faster than polar
thickness of exchange surface
(thinner the membrane, faster the rate)
Temperature - higher the temp, more kinetic energy, faster the rate
concentration gradient
(higher the diffusion, the faster the rate)
size of the molecule - smaller but faster
Equation for diffusion?
surface area x conc difference / distance of diffusion path
shape of graph?
straight line
proportional
Def of facilitated diffusion?
passive transfer of molecules or ions down a concentration gradient across a membrane, using a proton carrier in the membrane
limited by the number of ions present + the availability of channles
what does it do?
allows the diffusion of large polar molecules such as glucose or amino acids
carrier protein changes the shape to release the molecules to the other side of the membrane
shape of graph?
goes up in straight line then plateaus
Def of active transport?
the movement of molecules or ions across a membrane against the concentration gradient
using energy from the hydrolysis of ATP synthesised by the cell during respiratio
Features of Active transport?
Ions or molecules move from low to high concentration
If process requires energy, any factor affecting respiration will affect active transport
e.g cyanide
Active transport occurs in an intrinsic carrier protein
Limited by the number + availability of the carrier proteins
What are the processes using Active transport?
Muscle contraction
Nerve transmission
Reabsorption of Glucose in the nephron
Reabsorption of minerals by Plant root hairs
What does the graph look like?
Goes up then plateaus then goes straight down
Co transport?
a type of facilitated diffusion that allows molecules and ions into the cell together within the same transport protein molecule for co - transport in the ileum, kidney + nephron
what are the 3 steps?
a glucose molecule + 2 sodium ions attatched to a carrier protein in the cell membrane
the carrier protein changes shape + deposits the glucose + sodium into the cell
the glucose + sodium diffuse seperately through the cell
Glucose passes into the blood by FD + sodium = actively transported into the blood
Def of Osmosis?
the diffusion of water molecules from a region of high water potential to a region of low water potential through a selectively permeable membrane
Water potential?
the tendency of water molecules to move out of a system - measured in kPa
Pressure potential?
the pressure extended by the cell wall on the contents of the cell
Solute potential?
a measure of the Osmotic strength of a solution
Turgid?
when the entry of water = prevented as the cell wall no longer expands
Haemolysis of Red Blood cells?
Animal calls have no cell wall so as water enters the cell, the membrane can only withstand a certain pressure before it bursts
the water potential will be the same as the solute potential
if the red blood cell = placed in salt solution, the water leaves the cell + shrinks becoming crenated
What is the definition of Endocytosis?
when material is engulfed by extensions of the plasma membrane
Phagocytosis?
the uptake of solid material that is too large to be taken in by diffusion or active transport e.g Granulocytes engulf bacteria and a lysosome fuses with the vesicle which contains hydrolytic enzymes which digest the bacteria
products are absorbed into the cytoplasm
What is the def of Pinocytosis?
The uptake of liquid into vesicles which are smaller
Exocytosis?
process by which the substances leave the cell after they have been transported through the cytoplasm in a vesicle
the vesicle attaches to the plasma membrane , causing the membrane to change shape which require energy
exocytosis uses ATP, generated by respiration
