Biology - Cells and movement across membranes

Question 1

What are the main parts of an animal cell?

Answer 1

The main parts of an animal cell are the nucleus, cell membrane, cytoplasm and mitochondria.

Question 2

What are the main parts of a plant cell?

Answer 2

The main parts of a plant cell are the nucleus, cell membrane, cytoplasm, mitochondria, chloroplasts, cell wall made of cellulose and vacuole

Question 3

What additional features do plant cells have that animal cells don’t?

Answer 3

-Chloroplasts
-Cell wall made of cellulose
-Large central vacuole

Question 4

What is the function of a cell membrane - where is it found?

Answer 4

Controls the movement of substances into and out of the cell - Plant and animal cells

Question 5

What is the function of a cytoplasm - where is it found?

Answer 5

Jelly-like substance, where chemical reactions happen - Plant and animal cells

Question 6

What is the function of a nucleus - where is it found?

Answer 6

Carries genetic information and controls what happens inside the cell - Plant and animal cells

Question 7

What is the function of a mitochondria - where is it found?

Answer 7

Where respiration takes place, releasing energy for the cell - Plant and animal cells

Question 8

What is the function of a large central vacuole - where is it found?

Answer 8

Contains a liquid called cell sap, which keeps the cell firm - Plant cells only

Question 9

What is the function of a cell wall- where is it found?

Answer 9

Made of a tough substance called cellulose, which supports the cell - Plant cells only

Question 10

What is the function of a chloroplast - where is it found?

Answer 10

Contain the green pigment chlorophyll, which absorbs light energy. This is where photosynthesis occurs. - Plant cells only

Question 11

What is a light microscope?

Answer 11

It uses focused light passed through the object and two lenses to magnify an image of the object.

Question 12

What is a stage?

Answer 12

It has a hole in the centre which light can be focused up through the object.

Question 13

What is differentiation?

Answer 13

The process during which young, immature (unspecialized) cells take on individual characteristics and reach their mature (specialized) form and function.

Question 14

What is sucrose?

Answer 14

A disaccharide made from glucose and fructose. It is used as table sugar.

Question 15

What is concentration?

Answer 15

When sucrose is dissolved in water, the solute is sucrose and water is the solvent. Together they form a solution. The more sucrose particles there are in a certain volume of the solution, the more concentrated the solution is.

Question 16

What is an experiment for diffusion?

Answer 16

-Potassium permanganate is placed into a beaker of water.
-Particles diffuse from an area of high concentration to an area of low concentration.
-The contents of the beaker are now all the same concentration. The solution is now said to be in equilibrium.

Question 17

What is diffusion?

Answer 17

Diffusion is the movement of particles from a region where they are in high concentration to a region where they are in low concentration and is one of the ways substances can move across the cell membrane, into or out of the cell.

Question 18

What is a concentration gradient?

Answer 18

A concentration gradient exists when there is a region of high concentration leading to a region of low concentration:
-Going from high to low concentration is going down the concentration gradient
-Going from low to high concentration is going against the concentration gradient

Question 19

What is osmosis?

Answer 19

Osmosis is the diffusion of water molecules, from a region of higher concentration to a region of lower concentration, through a selectively permeable membrane.

Question 20

What do animal cells do because they don’t have a cell wall?

Answer 20

Animal cells do not have a cell wall. They change size and shape when put into solutions that are at a different concentration to the cell contents.

Question 21

What is an osmosis experiment?

Answer 21

Fill a Visking tubing with a mixture of starch and glucose. Visking tubing is an artificial selectively permeable membrane. Smaller molecules like water and glucose pass through its microscopic holes
larger molecules like starch and sucrose cannot pass through it. Test the water outside the Visking tubing for the presence of starch and glucose. Establish that the Visking is permeable to glucose but not to starch.

Question 22

What is active transport

Answer 22

Active transport is the movement of dissolved molecules into or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration. The particles move against the concentration gradient, using energy released during respiration.

Question 23

What is an enzyme

Answer 23

An enzyme is a protein that functions as a biological catalyst – a substance that speeds up a chemical reaction without being changed by the reaction.

Question 24

What is the lock and key model

Answer 24

In the lock and key model, the shape of the active site matches the shape of its substrate molecules. This makes enzymes highly specific – each type of enzyme can catalyse only one type of reaction (or just a few types of reactions).

Question 25

What is a denatured enzyme

Answer 25

To change the shape of an enzyme’s active site, for example because of high temperatures or extremes of pH. Denatured enzymes no longer work.

Question 26

What happens to enzymes at low temperatures

Answer 26

At low temperatures the enzymes and substrates have low kinetic energy. This results in the particles colliding less often, which means there will be fewer successful collisions between the substrate and the enzyme’s active site.

Question 27

What happens to an enzyme as the temperature increases

Answer 27

As the temperature increases, the kinetic energy increases, leading to more collisions and enzyme substrate complexes formed per unit time. This increases the rate of reaction.

Question 28

What happens if the temperature for the enzyme is too hot

Answer 28

If the temperature continues to increase past the optimum, the increased kinetic energy breaks the weak hydrogen bonds holding the enzyme’s unique active site shape. Enzyme–substrate complexes can no longer form as the substrates no longer fit into the active site. The enzyme is denatured.