Topic 1 - Key Concepts

Question 1

What is the function of the cell membrane?

Answer 1

Holds the cell together and controls what enters and leaves the cell

Question 2

Name 3 structures that are found in plant cells but not in animals cells

Answer 2

1) Cell wall
2) Chloroplasts
3) Vacuole

Question 3

Name the sub-cellular structures in plant cells where photosynthesis takes place

Answer 3

Chloroplasts

Question 4

What does haploid mean?

Answer 4

Half the amount of chromosomes that are in a normal cell. Haploid cells are gametes, and in humans they only have 23 chromosomes, not 23 pairs

Question 5

Give three ways in which an egg cell has adapted to its function

Answer 5

1) Contains nutrients in the cytoplasm to feed the embryo
2) Has a haploid nucleus
3) Straight after fertilisation, its membrane changes structure to stop any more sperm getting in. This makes sure that the offspring have the right amount of DNA

Question 6

What are cilia cells?

Answer 6

Specialised cells which are hair-like cells.

Question 7

What is the function of the ciliated cells that line the airway?

Answer 7

To move substances like mucus up the throat so it can be swallowed and does not reach the lungs.

Question 8

Give an advantage of using electron microscopes rather than light microscopes

Answer 8

Electron microscopes are more detailed than light microscopes, as they allow you to see sub-cellular structures

Question 9

Why do you have to use thin samples of tissue when viewing cells under a light microscope?

Answer 9

So that light can pass through the sample. If it is too thick, the sample will not be as clear and it may not work

Question 10

What equation would you use to find the size of a specimen using the magnification used and the size of the image seen through a microscope lens

Answer 10

image size (divided by) magnification

Question 11

How would you convert a measurement from mm to um?

Answer 11

x 1,000

Question 12

Which unit can be described as x 10-12m?

Answer 12

Picometre (pm)

Question 13

What part of an enzyme makes it specific to a particular substrate?

Answer 13

Active site

Question 14

Why can denatured enzymes no longer catalyse chemical reactions?

Answer 14

Because the active site has changed shape, meaning it cannot fit the substrate

Question 15

How does temperature affect enzyme activity?

Answer 15

It changed the rate of an enzyme-catalysed reaction. if it gets too hot, some of the bonds that hold the enzyme together will break, which changes the shape of the active site, so the substrate will not fit anymore.

Question 16

How could you investigate the effect of pH on the rate of amylase activity?

Answer 16

1) Put iodine sample on each well of a spotting tile
2) Using a bunsen, heat-proof mat and a tripod & gauze, put a beaker of water on top and heat the water until it is at 35 degrees
3) Use a syringe to add 3cm3 of amylase solution and 1cm3 of buffer solution with a pH of 5 to a boiling tube, and put it in the beaker of water and wait for 5 minuets
4) Add 3cm3 of starch solution of a boiling tube. mix the contents and start a stop clock.
5) Use continuous sampling to record how long it takes for the amylase to break down all of the starch. Use a dropping pipette to take a fresh sample every 10 seconds and put a drop into the well with iodine solution.
6) When the iodine remains a brown/orange, starch is no longer present

Question 17

Which two molecules are produced when lipids are broken down?

Answer 17

Fatty acids and glycerol

Question 18

Name a molecule that is formed from simple sugars

Answer 18

Carbohydrates

Question 19

What is the colour change that occurs when Benedict’s solution is added to a substance containing reducing sugars?

Answer 19

Blue - green - yellow - orange - red

The higher the concentration of reducing sugar, the further up the colour change goes

Question 20

What chemical solution is used to test the presence of starch?

Answer 20

Iodine

Question 21

How would you test for the presence of lipids in a sample?

Answer 21

Use the emulsion test

1) Shake the test substance with ethanol for 1 minute until it dissolved, then pour it into water
2) If there are any lipids present, they will precipitate out of the liquid and show up as a milky emulsion
3) The more lipid there is, the more noticeable the milky colour will be

Question 22

What is diffusion?

Answer 22

The net movement of particles from an area of higher concentration to an area of lower concentration

Question 23

What is osmosis?

Answer 23

The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to an region of lower water concentration

Question 24

What is active transport?

Answer 24

The movement of particles across a membrane against a concentration gradient using energy transferred during respiration

Question 25

What is the biuret test?

Answer 25

Test for proteins

1) Add a few drops of potassium hydroxide solution to make the solution an alkaline

2) Add some copper(II) sulfate solution which is bright blue
- If there is no protein, the solution will stay blue
- If there is protein present, the solution will turn
purple