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21 Cards in this Set

  • Front
  • Back

Why was the name 'fluid mosaic model' given?

Fluid means that the phospholipids are constantly moving.


Mosaic describes the arrangement of the molecules in the membrane.

What does the fluid mosaic model of the cell membrane look like?

Explain the roles for phospholipids and cholesterol.

Phospholipid - Have a hydrophilic head and hydrophobic tail. The centre of the bilayer is hydrophilic because the membrane doesn't allow water-soluble substances to allow pass through it. Small, non-polar substances and water can diffuse through it.


Cholestrol - gives the membrane stability because it binds to the tails of the phospholipids, causing them to pack closely which restricts movement.

How do temperatures affect the membrane permeability?

Temperatures below 0°c - The phospholipids can't move a lot. The channel and carrier proteins in the membrane denature increasing the permeability. Ice crystals may form and pierce the membrane, making it highly permeable when it thaws.


Temperatures between 0°c and 45°c - they can move around more. As the temperature increases the phospholipids move more because they have more energy, increasing the permeability.


Temperatures above 45°c - The bilayer melts down. Water inside the cell's expands. The carrier and channel proteins denature so they can't control what leaves or enters the cell. Which evidently increases the permeability.

How can you investigate the cell membrane permeability?

What is diffusion?

It is the net movement of particles from an area of high concentration to an area of low concentration. It moves down a concentration gradient.

What is simple diffusion?

When molecules diffuse directly through a cell membrane.

Name some factors that can affect diffusion.

Concentration gradient - The higher it is, the faster diffusion will be. This will lead up to both sides of the membrane being in equilibrium; diffusion slows over time.


Thickness of exchange surface - thinner the exchange surface, the quicker the diffusion is because they'd have a shorter distance.


Surface area - Larger means diffusion will happen quicker.

What is facilitated diffusion?

Net movement of particles from a high concentration to a low concentration, using carrier proteins (carries large molecules) and channel proteins (carries charged particles).

Name factors affecting the rate for facilitated diffusion.

Concentration gradient - higher concentration gradient means that the faster the rate of diffusion is.


Number of channel or carrier proteins - if all of the proteins are occupied then that means facilitated diffusion can't happen any quicker.

What is osmosis?

Diffusion of water molecules across a partially permeable membrane, from an area of higher water potential to an area of low water potential.

What is the water potential of pure water?

Zero

What does it mean if cells are in a ... solution:


• Isotonic


• Hypertonic


• Hypotonic

Isotonic - Two solutions have the same water potential.


Hypertonic - Solutions with lower water potential than the cell.


Hypotonic - Solutions with high water potential than the cell.

Name some factors affecting the rate of osmosis.

Water potential gradient - higher the gradient, faster the rate of osmosis.


Thickness of exchange surface - thinner exchange surface, faster the rate of osmosis.


Surface area of the exchange surface - Larger surface area means more quicker osmosis occurs.

How would you make serial dilutions?

How does active transport work?

It uses energy (gained by hydrolysing ATP) to move molecules and ions across plasma membranes, usually against a concentration gradient. Carrier proteins and co-transporters are involved in active transport.

Two main differences between facilitated diffusion and active transport?

• Active transport requires energy.


• Active transport usually moves solutes from a low concentration to a high concentration.

How is glucose absorbed in the lumen?

Factors affecting the rate of active transport?

Speed of individual carrier proteins - faster they work, the faster the rate of active transport.


Number of carrier proteins present - more proteins there are, the faster the rate of active transport.


• The rate of respiration into he cell and the availability of ATP. If respiration is inhibited, active transport can't take place.

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What is the function of glycolipids and glycoproteins?

Glycolipids - help maintain stability, help cells attach to one another and act as recognition sites.


Glycoproteins - act as recognition sites, help cells attach to one another and allow cells to recognise one another.