Biology: Diffusion, Osmosis and Active Transport

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How does increasing the temperature increase the rate of diffusion?

The particles have more kinetic energy and so they move around faster

Name four molecules that can diffuse through a cell membrane

oxygen, glucose, amino acids and water

1. cut equal-sized pieces of potato 2. blot with tissue paper and weigh 3. put pieces into different concentrations of sucrose solution for a few hours 4. remove, blot with tissue paper and reweigh

Describe the brief method for investigating osmosis in a potato cells

How does increasing the surface area increase the rate of diffusion?

A larger surface area means that more particles can cross the membrane in the same amount of time

Define osmosis

A special type of diffusion where water moves from a high concentration to a low concentration (down a concentration gradient) through a partially permeable membrane.

Identify three places in the body where diffusion takes place

Across the alveoli in the lungs, across a synapse between neurones, across the wall of the small intestine.

How are mineral ions absorbed into the root hair cells?

Active transport

How is active transport different to osmosis and diffusion?

Active transport uses energy compared to diffusion and osmosis that does not. Active transport moves substances against the concentration gradient, whereas diffusion and osmosis move substances down the concentration gradient

Why do plant cells not burst when they are placed in a hypertonic solution.

Because the have a strong cell wall

If blood cells are placed in a hypotonic solution they.........?

Burst

The rate of diffusion is affected by....

Concentration gradient, temperature and surface area

Define the term diffusion

Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration (down a concentration gradient)

Give an example of where active transport occurs in humans

Glucose is absorbed from the lower gut into the blood where there is a higher concentration of glucose

percentage change in mass = start mass _______________ x 100 end mass

How do you calculate the change in mass of a potato chip when placed in a salt solution

Cells which are involved in active transport contain lots of which organelle?

Mitochondria to provide the energy for active transport

By what process does water move into a plant?

Osmosis

Which part of a plant is involved in the uptake of water?

Root hair cell

If blood cells are placed in a hypertonic solution they ..........?

Shrivel

Define the term hypotonic

The concentration of solutes outside the cell is lower that the concentration of solutes inside the cell

Define the term hypertonic

The concentration of solutes outside the cell is greater than the concentration of solutes inside the cell

Define the term Isotonic

The concentration of solutes outside the cell is the same as the concentration of solute inside the cell

Define active transport

The movement of substances from an area of low concentration to high concentration. Movement is against the concentration gradient

Why is osmosis important in plants?

To maintain plant cell turgor. (so plants can support their stems and leaves)

State two different adaptations that are found in living organisms to make gas exchange more efficient

Ventilation systems and circulating blood to help maintain a steep concentration gradient

Osmosis refers the the movement of ????? molecules

Water

Describe what happens to a cell when it becomes plasmolysed

When a plant cell loses water by osmosis, the vacuole and cytoplasm shrinks and the cell membrane pulls away from the cell wall

Where the line crosses the horizontal axis at 0% change in mass, the sucrose concentration is equal to the concentration of the contents of the potato cells. The sucrose concentration is isotonic with the cells' cytoplasm, so there is no net movement of water by osmosis

When plotting the change in mass of potato chips in different sucrose concentrations. What does the point at which the line crosses the horizontal line represent


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