AQA GCSE Biology - Movement in cells

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Define the term diffusion.

Diffusion is the spreading out of particles in a solution or a gas

What is a concentration gradient?

A concentration gradient is a difference in concentration between two regions.

True or False? Diffusion is an active process.

False. Diffusion is a passive process that occurs when molecules spread out due to their random movement.

What is a partially permeable cell membrane?

A partially permeable cell membrane allows some substances to pass through while preventing others from entering or leaving a cell.

Name an example of diffusion that takes place in the human lungs.

Examples of diffusion in the lungs include: oxygen diffuses from the inhaled air into the blood through the alveolar lining

True or False? The waste product urea diffuses from body cells into the blood.

True. Urea is a metabolic waste product produced in the cells. It diffuses into the blood before being excreted by the kidneys.

What is the relationship between surface area and rate of diffusion into a cell?

As surface area to volume ratio increases

What is the effect of increasing temperature on the movement of particles?

At higher temperatures particles move around faster; this is because they have more kinetic energy.

True or False? Increasing temperature decreases the rate of diffusion.

False. As temperature increases

True or False? Increasing the concentration gradient will increase the rate of diffusion.

True. As concentration gradient increases the rate of diffusion also increases.

Define the phrase surface area to volume ratio.

Surface area to volume ratio is the surface area of an object in relation to its volume.

What happens to the surface area to volume ratio as cell size increases?

As cell size increases the surface area to volume ratio decreases.

Why do multicellular organisms need exchange surfaces and transport systems?

Multicellular organisms need exchange surfaces because their small surface area to volume ratio means that exchange of substances at their body surface is too slow to meet their needs. Multicellular organisms need transport systems because of their large volume; their bodies contain many layers of cells

What are the features of an efficient exchange surface?

Features of an exchange surface include: A large surface area

True or False? The alveoli provide an exchange surface in mammals.

True. The alveoli provide an exchange surface for gas exchange between the lungs and the blood.

How do the alveoli aid gas exchange?

Alveoli facilitate gas exchange as follows: They have a large surface area

What is the function of stomata in leaves?

Stomata are tiny openings that allow air to move in and out of leaves. This decreases the diffusion distance for gas exchange inside the leaf.

What is the name of the leaf cell type across which gas exchange occurs inside leaves?

Gas exchange occurs between the leaf air spaces and the interior of the spongy mesophyll cells.

How are fish gills adapted for efficient gas exchange?

Fish gills are adapted for gas exchange as follows: Many filaments covered in lamellae increase the surface area

True or False? Villi in the small intestine of mammals have a large surface area but are not well supplied with blood.

False. The villi in the small intestine do have a large surface area

Define the term osmosis.

Osmosis is the diffusion of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution)

True or False? Only water can move by osmosis.

True. Only water can be transported by osmosis.

What type of concentration difference leads to osmosis?

The type of concentration difference that leads to osmosis is a difference in water concentration between two regions. This can also be referred to as water potential.

True or False? Osmosis only occurs across a partially permeable membrane.

True. Osmosis must take place across a partially permeable membrane. If water moves in any other way

Define the term dependent variable.

The dependent variable is the variable that is measured during an investigation.

What is the independent variable in the practical that investigates osmosis using potato cylinders?

The independent variable in the osmosis and potato practical is the solute concentration of the solution in which the potato cylinders are placed.

In the osmosis and potato practical

why is it important to dry the potato cylinders before weighing?

Why is it important that all pieces of potato have the same surface area when measuring the effect of concentration of salt or sugar solution on the mass of plant tissue?

It is important that all pieces of potato have the same surface area when measuring the effect of concentration of a solution on the mass of plant tissue because surface area affects osmosis

True or False? Potato cylinders placed in distilled water should gain mass due to osmosis.

True. Potato cylinders placed in distilled water will gain mass due to the movement of water into the cells by osmosis. This will occur because distilled water has a higher water concentration than potato cell cytoplasm.

Give one example of a control variable in the osmosis and potato practical.

Examples of control variables in the osmosis and potato practical include: Volume of (e.g. sucrose) solution

True or False? When a potato cylinder placed in a sucrose solution does not change in mass

this indicates no overall movement of water.

What is the purpose of repeating the osmosis experiment with multiple potato cylinders?

Repeating the experiment with multiple potato cylinders allows for the identification and exclusion of anomalous results when calculating the mean.

What is the equation used to calculate the percentage change in mass for each potato cylinder?

The equation used to calculate the percentage change in mass for each potato cylinder is: percent change in mass = ((final mass - initial mass) ÷ initial mass) × 100.

When plotting a graph of the results of the osmosis and potato experiment

how can the concentration of sugar/salt inside the potato cells be estimated?

Define the term active transport.

Active transport is the movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration; this requires energy.

True or False? Active transport is the movement of particles down a concentration gradient.

False. Active transport moves particles against a concentration gradient.

Which cellular process releases energy for active transport?

Energy for active transport is released during the cellular process of respiration.

Why do root hair cells use active transport?

Root hair cells use active transport to move mineral ions from a region of lower concentration in the soil to a region of higher concentration inside the cell cytoplasm.

How does active transport aid glucose absorption in the small intestine?

Active transport allows glucose to be transported into the bloodstream from the lumen of the small intestine when the concentration of glucose in the blood is higher than that in the intestine.

Compare the energy requirements of diffusion

active transport and osmosis.

How do diffusion

active transport and osmosis differ in terms of concentration gradients?

Which cell transport mechanism(s) can only take place across a cell membrane?

Cell transport mechanisms that can only take place across a cell membrane are: Osmosis