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Back to AI Flashcard MakerBiology /LGS A-Level OCR Biology - Unit 2 - Diffusion/Osmosis/Active Transport Part 3

LGS A-Level OCR Biology - Unit 2 - Diffusion/Osmosis/Active Transport Part 3

Biology26 CardsCreated about 1 month ago

This deck covers key concepts and questions related to diffusion, osmosis, and active transport, as outlined in the LGS A-Level OCR Biology curriculum.

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Why are ions only able to cross a membrane through a protein channel?

  • protein channels provide a hydrophilic channel through the membrane

  • ions cannot pass through membranes without them due to the hydrophobic centre of the phosphoplipid bilayer

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Key Terms

Term
Definition

Why are ions only able to cross a membrane through a protein channel?

  • protein channels provide a hydrophilic channel through the membrane

  • ions cannot pass through membranes without them due to t...

How can the effect of surface area on the rate of diffusion be investigated?

  • agar made with phenolpthalein and NaOH is pink as NaOH is alkai

  • cubes of different sizes are placed in HCl

  • In...

How can the effect of temperature on the rate of diffusion be investigated?

  • an artificial cell is made from dialysis tubing

  • solution is placed in cell

  • cell is placed in water bath at di...

What is the effect of a higher surface area to volume ratio on the rate of diffusion?
It increases the rate of diffusion.
What is the symbol of water potential?
Ψ
What are the units of water potential?
kPa
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LGS A-Level OCR Biology - Unit 2 - Diffusion/Osmosis/Active Transport Part 3
TermDefinition

Why are ions only able to cross a membrane through a protein channel?

  • protein channels provide a hydrophilic channel through the membrane

  • ions cannot pass through membranes without them due to the hydrophobic centre of the phosphoplipid bilayer

How can the effect of surface area on the rate of diffusion be investigated?

  • agar made with phenolpthalein and NaOH is pink as NaOH is alkai

  • cubes of different sizes are placed in HCl

  • In HCl the cubes will go colourless

  • Leave for 5 minutes

  • measure the volume of cube that is still pink

  • calculate % diffusion

How can the effect of temperature on the rate of diffusion be investigated?

  • an artificial cell is made from dialysis tubing

  • solution is placed in cell

  • cell is placed in water bath at different temperatures

  • indicators can be used to see the rate of diffusion (e.g. iodine for starch or benedict's solution for glucose)

What is the effect of a higher surface area to volume ratio on the rate of diffusion?
It increases the rate of diffusion.
What is the symbol of water potential?
Ψ
What are the units of water potential?
kPa
What is water potential?
The pressure exerted by water molecules as they collide with a membrane or container.
What is the Ψ of pure water?
0

Why does water potential decrease as solute is added?

  • when a substance is dissolved in water the kinetic energy of the water is lowered

  • because water molecules aggregate around the solute

  • movement of water molecules is partially impeded

  • so a lower pressure is exerted

What is a hypertonic solution?
Having a higher concentration of solute relative to another solution.

What is an isotonic solution?

having the same concentration of solute relative to another solution

What is a hypotonic solution?

having a lower concentration of solute relative to another solution

What is the usual water potential in animal cells?
About 50kPa

What would be the effect of placing a red blood cell in a hypotonic solution?

  • net movement of water into the cell

  • cell swells and bursts

  • causing haemolysis

  • cell contents lost, haemoglobin released

What would be the effect of placing a red blood cell in a hypertonic solution?

  • net movement of water out of the cell

  • cell shrinks and shrivels

  • becomes darker in colour as haemoglobin is more concentrated

  • crenation

What would be the effect of placing a plant cell in a hypotonic solution?

  • net movement of water into cell

  • cell becomes turgid

  • protoplast pushed against cell wall

What would be the effect of placing a plant cell in a hypertonic solution?

  • net movement of water out of cell

  • contents shrink

  • cell plasmolysed

  • protoplast completely pulled away

When a plant cell is placed in a hypertonic solution, what fills the space between the cell wall and the protoplast?
The external solution with a more negative water potential.
Why do plant cell walls not burst from osmosis?
They have strong cellulose walls which are able to resist the hydrostatic pressure.
What happens to the volume of cytoplasm when a plant cell is placed in a hypertonic solution?
Volume of cytoplasm decreases.

How can the concentration of a potato be determined?

  • weight pieces of equal size potato

  • place in different concentrations of solution

  • leave potato for the same time

  • blot potato dry and reweigh

  • calculate % change in mass

  • plot on graph

  • where line of best fit crosses 0 on x-axis shows concentration of potato

Define precision
The closeness of two or more measurements to each other.
Define accuracy
The closeness of a measured value to a standard or known value.
Define repeatability
If you repeat the experiment, how close are your results to other results you have collected.
Define reproducibility
If someone else repeats the experiment how close are their results to yours.
Describe the routes that water molecules take through the cell surface membrane
Diffuse between phospholipids, move through aquaporins.