🍄 | Unit 3 & 4 | Movement in and out of Cells & Biological Molecules

Question 1

What is diffusion?

Answer 1

Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration, down a concentration gradient, as a result of random particle movement.

Question 2

Definition of “partially permeable”

Answer 2

some molecules are allowed to cross easily, where as other molecules with difficulty or not at all.

Question 3

How permeable is the cell membrane of a cell?

Answer 3

The cell membrane of every cell is partially permeable. This restricts the free movement of molecules that are diffusing.

Question 4

Diffusion enables cells to…

Answer 4

∘ get rid of some of their waste products
∘ obtain many of their requirements for nutrition, growth, etc.
∘ allow gas exchange for respiration

Question 5

Diffusion in the small intestine

Answer 5

Absorption - the movement of digested nutrient molecules through the small intestine wall and into the blood

Question 6

Diffusion in leaves

Answer 6

∘ Oxygen from the air spaces between mesophyll cells to the mitochondria in all the plant cells.

∘ Carbon dioxide from the air spaces between mesophyll cells to the chloroplasts of mesophyll cells.

Question 7

Definition of “Brownian Motion”

Answer 7

Brownian motion is the random movement of particles caused by large collisions with smaller, often invisible particles.

Question 8

How do substances move in and out of cells?

Answer 8

Substances move in and out of cells by diffusion.

Question 9

Where does the energy for diffusion to take place come from?

Answer 9

The energy for diffusion comes from the kinetic energy of the random movement of particles.

Question 10

How are cells adapted to speed up diffusion of molecules in and out of them?

Answer 10

They’re structure has adapted in a way that increases the surface-area-to-volume ratio of the cell. (eg. epithelial cells in the small intestine, root hair cells in plants - both have extensions of the cytoplasm)

Question 11

Factors affecting the rate of diffusion

Answer 11

∘ Distance
∘ Temperature
∘ Concentration gradient

Question 12

Is a dilute solution a region of high water potential or a region of lower water potential?

Answer 12

A dilute solution is a region of higher water potential.

Question 13

IS a concentrated solution a region of high water potential or a region of lower water potential?

Answer 13

A concentrated solution is a region of lower water potential.

Question 14

How does water diffuse in and out of cells?

Answer 14

Water diffuses in and out of cells by osmosis.

Question 15

What happens to a plant cell when it is put in a concentrated solution?

Answer 15

The water in the plant cell moves out of the cell by osmosis. The cell plasmolyses and decreases in mass, becoming flaccid.

Question 16

What happens to a plant cell when placed in distilled water?

Answer 16

The water moves into the plant cell by osmosis, and the cell swells and increases in mass. It becomes turgid as a result of the turgor pressure on the cell walls of the plant.

Question 17

How does distance affect the rate of diffusion?

Answer 17

The smaller the distance molecules need to travel, the faster diffusion will occur

Question 18

How does temperature affect the rate of diffusion?

Answer 18

The higher the temperature, the more kinetic energy particles will have, resulting in more collisions between molecules and the cell membrane.

Question 19

How does the concentration gradient affect the rate of diffusion?

Answer 19

The greater the difference in the concentration on either side of the diffusion site, the faster diffusion will occur.

Question 20

Why are water potential and osmosis in the uptake of water important?

Answer 20

The water potential in the soil must be higher than the water potential in the roots, to ensure that water diffuses into the plant and enters the plant cells.
This will apply turgor pressure to their cell walls, making them turgid, which will help them support the plant’s structure.

Question 21

Why are water potential and osmosis important in animal cells and tissues?

Answer 21

If there is a higher water potential inside the animal cells than outside, water in the cells will diffuse out by osmosis. This causes a dramatic decrease of water in the blood, which is not healthy for the animal.

Question 22

Where does the energy for diffusion come from?

Answer 22

The energy for diffusion comes from the kinetic energy of the random movement of molecules and ions.

Question 23

Differences in osmosis of plants and animals

Answer 23

∘ animal cells can be permanently damaged by osmosis,
plant cells cannot be permanently damaged
∘ In plants, the cell walls give the cell structural support
With water loss, animal cells can shrink,
With too much water, animal cells can burst

Question 24

How do protein molecules move particles across a membrane during active transport?

Answer 24

Carrier proteins