Transport in cells

What is diffusion?

The spreading out of particles in a solution or gas, resulting in net movement of particles form a region of high concentration to a region of low concentration down the concentration gradient

What is a concentration gradient?

The difference in concentration between two regions

Is diffusion an active process?

no, diffusion is a passive process that occurs when molecules spread out due to their random movement therefore it requires no energy

What is a partially permeable membrane?

A substance that allows certain substances to enter and leave the cell

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

as surface area to volume ratio increases, so does the rate of diffusion

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

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

What are the features of an efficient exchange surface?

• a large surface area

• a short diffusion distance

• a steep concentration gradient maintained by a good blood supply and a good supply of required substances

How do the alveoli aid gas exchange?

• they have a large surface area

• their walls are thin

• they have a good blood supply

• they are well ventilated

What is the function of stomata in leaves?

they have tiny openings that allow air to move in and out, which 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?

spongy mesophyll cells

What is osmosis?

The diffusion of water molecules from a region of high concentration to a region of low concentration

What is a dependent variable?

the variable that is MEASURED

What is an independent variable?

the variable that is MEASURED

In the osmosis and potato practical, why is it important to dry potato cylinders before weighing?

to remove any surface water that could affect the mass measurment

What is a control variable?

the variable that is kept the SAME

What is active transport?

The movement of particles across a membrane from a region of lower concentration to high concentration which requires energy

Which cellular process releases energy for active transport?

Respiration

Why do root hair cells use active transport?

To move mineral ions from a region of low 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?

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

Which cell transport mechanisms can only take place across a cell membrane?

• osmosis

• Active transport

Why do plants need mineral ions?

For Growth

Why are plants not able to rely on diffusion to absorb mineral ions form the soil?

The concentration of minerals is higher inside the plant cells than in the soil so the minerals would move out go yeh plants cells by diffusion

What are two ways that active transport differs from diffusion?

• active transport requires energy

• Active transport moves against the concentration gradient

How does the structure of a root hair cell help it to carry out its function?

They have elongated hairs that stick out into the soil which gives the root a large surface area for absorbing substances