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36 Cards in this Set

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Function of a cell surface membrane?

Barrier between cell and its environment, controlling what comes in and out

What are membranes made up of?

Lipids, proteins and glycoproteins, glycolipids

Describe the fluid mosaic model?

Fluid because the phospholipids are constantly moving and mosaic because of the way the proteins are scattered through the bilayer like a mosaic

Describe a phospholipid?

Barrier to water soluble substances


Hydrophilic head and a hydrophobic tail


In a bilayer


Does not allow water soluble substances like ions and polar molecules

What does cholesterol do in a phospholipid bilayer?

Gives the membrane stability


It binds to the hydrophobic tail and causes them to pack closely together, makes the membrane more rigid

What does cholesterol do in a phospholipid bilayer?

Gives the membrane stability


It binds to the hydrophobic tail and causes them to pack closely together, makes the membrane more rigid

What happens to membranes in a temperature below 0 degrees?

Dont have much energy so they don’t move as much, therefore they pack closer together, channel proteins and carrier proteins denature , increasing permeability, ice crystals may form and pierce the membrane making it even more permeable

Definition of diffusion?

Net movement of particlrs from an area of high concentration to an area of low concentstion

Is diffusion a passive process?

Yes

What factors affect the rate of diffusion?

How high a concentration graduent is


Thickness of the exchange surface


Surface area

Why does facillitated diffusion happen?

Large molecules diffuse slowly through and charge particles because they are water soluble diffuse slowly

What helps facilitated diffusion happen?

Carrier proteins and channel proteins

Is facilitated diffusion a passive process?

Yes

How do carrier proteins work?

Large molecule attaches


Protein changes shape


Then releases it on the other side

How do carrier proteins work?

Large molecule attaches


Protein changes shape


Then releases it on the other side

How do channel proteins work?

Charged particle diffuses down its concentration gradient across the channel

Factors affecting the rate of facilitated diffusion?

Height of the concentration gradient


Number of channel or carrier proteins

Definition of osmosis?

Diffusion of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential

Definition of osmosis?

Diffusion of water molecules across a partially permeable membrane from an area of high water potential to an area of low water potential

Definition of water potential?

Is the likelihood of water molecules to diffuse in or out of a solution

What is the water potential of pure water?

Zero

What is the water potential of pure water?

Zero

What happens if you add a solute to pure water?

Water potential becomes negative

What is an isotonic solution?

Two solutions with the same water potential

What is an hypotonic solution?

Solution with a higher potential than the cell, cell will swell

What is a hypertonic solution?

Lower water potential than the cell


Cell will shrink

Factors affecting rate of osmosis?

Water potential gradient


Thickness of exchange surface


Surface area

What is a serial dilution?

Create a set of solutions that decrease in concentration by the same factor each time

How to make a serial dilution?

1. Line uo 5 test tubes


2. Add 10cm3 of the 2M sucrose solution to the first test tube and 5cm3 of distilled water to the others.


3. Then using a pippette draw 5cm3 of the solution and add it to the next one. Now have 10cm3 of the solution, so now that one is 1M


4.repeat the process three more times to create solutions of 0.5M,0.25M,0.125M

How to work out the scale factor?

Concentration of the solution/concentration od the solution you want to make

How to calculate the percentage change in mass in the potato chips?

1. Use a cork borer to cut potato into identically sized chips. Measure mass.


2. Place one group into each sucrose solution for 20 mins.


3.remove chips and pat dry. Weigh each group and calc percentage change.

What to do after you have weighed the potato chips a second time?

Produce a calibration curve by plotting percentage change in mass against concentration

Differences between active transport and facilitated diffusion?

Active transports moves solutes from low to high concentrations, whereas facilitated high to low


Active transport needs energy

What do co transporters do?

Bind two molecules and use the concentration gradient of one to move the other molecule agaisnt its own

Explain the absorption of glucose?

Na+ are actively transported out of epithelial cells in to the blood, this creates a conc gradient of sodium ions


This causes Na+ to diffuse into the epithial cells. The sodium-glucose co transporter carries glucose into the cell aswell. As a result conc of glucose inc


Glucose then diffuses into the blood

Factors affceting rate of active transport?

Speed of carrier proteins


Number of carrier proteins


Rate of respiration