Topic 2- Genes And Health Flashcards
What is the concentration gradient?
The difference in concentration between two areas.
A larger concentration gradient results in a faster rate of diffusion.
How does temperature, surface area and membrane thickness affect rate of diffusion?
Higher temperatures increase the rate of diffusion because molecules move faster at higher temperatures, facilitating quicker movement.
Larger surface area results in a faster rate of diffusion as more area allows more molecules to pass through simultaneously.
Thicker membranes slow down the rate of diffusion as a thicker barrier requires more time for molecules to pass through.
Describe these transport processes, what they’re used by and what effects their rate:
Active transport?
Diffusion?
Facilitated diffusion?
1.The movement of substances against the concentration gradient which requires energy. Energy from ATP is used to change the shape of the carrier protein and allow substances to be released on the other side.
- The surface area of a membrane and the number of carrier proteins
- The passive net movement of particles in fluids from a high to a low concentration.
Used by small (co2) or non-polar molecules (o2) to pass directly through the membrane.
- Temperature, Surface area and thickness of exchange surface. - A passive process where molecules diffuse through carrier or channel proteins across membrane down conc. gradient.
- Used by large molecules as they’re too big and polar molecules as they get repelled by hydrophobic fatty acid tails due to insolubility.
- The rate of facilitated diffusion increases with more proteins and a higher concentration gradient.
What changes occur in carrier proteins during active transport?
Energy from ATP causes the carrier protein to change shape, releasing the substance on the other side.
What was the original fluid mosaic model based on?
What were it’s issues? (2)
An electron micrograph called the ‘sandwich model’.
1. Didn’t allow hydrophilic phosphate heads to contact water
2. Didn’t keep hydrophobic, non-polar amino acids away from water.
What is the evidence from reinterpretation of fluid mosaic model EM?
Re-interpretation showed phosphate heads were more electron dense so were the darker part and the fatty acid tails were lighter and on the inside
What is the evidence for fluid mosaic model from removing proteins?
It showed 2 types of protein, some could be easily removed by increasing the ionic strength of a solution and some could only be removed with a strong detergent.
Why does evidence from removing proteins support the FM model?
As there is loosely attached peripheral proteins and integral proteins which are fully embedded.
What are the 3 steps for evidence from freeze fracture EM?
- Freeze the membrane then break between the layers
- Coat the inner fractured surface with a heavy metal.
- Use a scanning EM to get a 3D image
FICKS LAW:
What 3 properties is the rate of diffusion dependant on?
- SA: Rate of diffusion = directly proportional to surface area
- Concentration gradient to rate of diffusion is directly proportional to difference in concentration
- Thickness of exchange surface to ROD is inversely proportional to thickness of surface
What is Ficks Law equation?
ROD is directly proportional to SA X difference in concentration gradient divided by thickness of exchange surface
What does the cell membrane include? (5)
- Phospholipid bilayer
- Integral proteins
- Peripheral proteins
- Cholesterol
- Carbohydrates
• What is the structure of the phosphoripid bilayer? (3)
2 fatty acid hydrophobic tails, 1 hydrophilic negatively charged phosphate group, 1 glycerol group
What happens to the phospholipids in a wet environment?
They form a bilayer, they could form a Micelle but favour bilayer as the fatty acid tails are too bulky
Where is cholesterol found + what does it do?
- It is a lipid which sits in the core of the membrane but not in bacteria
- It makes it more rigid
What increases the fluidity of the membrane?
High temperatures increase the fluidity which increase the permeability
What is the permeability?
Semi permeable
What do glycoproteins and lipids do? (2)
- They form hydrogen bonds with water outside the cell which stabilises it
- They act as signalling receptors with active binding sites for communication molecules like hormones and drugs
What are saturated phospholipids? (2)
They have NO DOUBLE BOND and their tails are easier to compact
What are unsaturated phospholipids? (3)
- Have a double bond
- Kinked tails
- Can’t fit together nicely
Which type of saturation makes the cell membrane more fluid?
Unsaturated
How did freeze fracture EM support Model?
It showed a smooth mosaic like structure interspersed with larger particles.
What were the 3 steps of evidence from using labelled tracers?
- Lectin (molecules that bind to polysaccharides) were labelled with ferritin which can be seen under EM. 2. It was mixed with membrane samples. 3. The lectin only bound to the surface of the membrane.
How did evidence from labelled tracers support the FMM?
They showed that the membrane is asymmetrical.
What were the 3 steps of evidence from mouse + human cells?
- Label mouse membrane proteins green and humans red. 2. Fuse the cells. 3. Use microscope to view labelled protein movement.
What was observed from mouse and human cell FMM evidence and how does it support?
First, the coloured membranes stayed in their halves but after an hour at 37 degrees they completely mixed. This can only happen via diffusion so shows the membrane is fluid.
What are the 3 types of Channels?
Channel proteins, gated channels and carrier proteins.
What are channel proteins?
They are water filled channels that allow polar molecules and ions to pass through to avoid the hydrophobic layer of membrane.
What are gated channels?
A type of channel that requires a signal to open like a hormone or change in voltage.
What happens at a carrier protein?
- An ion or molecule like sugar, amino acids or nucleotides bind to the proteins site. 2. The protein changes shape to allow them to pass through.
Which side of a carrier protein has more binding?
The side with more molecules as it carries them down the concentration gradient.
What is osmosis?
The net movement of water molecules from a dilute to a concentrated solution through a partially permeable membrane.
What does isotonic mean?
Equal water potential both sides of cell membrane.
What are the 2 types of active transport?
Endocytosis and exocytosis.
What is Exocytosis?
- The bulk removal of substances from a cell using ATP. 2. Vesicles fuse with the membrane and release substances within to the surroundings like the release of insulin from the blood.
What is Endocytosis?
- The bulk transport of substances into a cell using ATP. 2. Part of the membrane buds off to become a vesicle which engulfs the substance and releases it into the cell like cholesterol into cells.
How does ATP provide energy?
Very little energy is required to break the bond holding the third phosphate
The phosphate becomes hydrated
Lots of energy is released as the bonds form between water and the third phosphate
What is the point of regulating water content of mucus?
To maintain a consistent viscosity
What happens if mucus water content is:
Too runny?
Too thick?
- It floods the airways
- It cant get beaten out of the lungs by cilia.
What are the consequences of unregulated mucus water content for CF patients? (3)
Theyre mucus is too thick so cant be beaten out of the lungs, which causes lung infections as the bacteria are trapped.
Their white blood cells break down and their DNA makes the mucus stickier.
The inflammation leads to lung damage. This is an example of a positive feedback loop
How is mucus water content regulated?
By the transport of sodium and chloride ions across epithelial cells which causes water to follow them via osmosis
What does ENaC’s stand for?
What does CFTR stand for?
- Epithelial sodium ion channels
- Cystic fibrosis transmembrane conductance regulator which is a type of gated channel
What happens when there is excess water in the mucus?
- Sodium ions are actively pumped across the basal membrane and then diffuse through open ENaC’s in apical membrane.
- The chloride ions diffuse down the electrical gradient into tissue fluid and CFTR channels close.
- Water is drawn out of cell via osmosis due to higher conc. of salts in tissue fluid
- Water is drawn back into cell
What happens when too little water in the mucus?
- Chloride ions are pumped across the membrane and diffuse out of the open CFTR channels at top of membrane.
- Sodium ions diffuse down the electrical gradient into the mucus and the ENaCs close
- The elevated salt concentration in the mucus draw water out of the cell by osmosis.
What is wrong with mucus water content regulation process in CF patients?
- The CFTR protein is non functional or absent
- The ENaC is constantly open so may let more sodium than normal in
- So water is continuously removed from mucus and drawn into the cell.
