Topic 1 - Key Concepts In Biology (both papers - important!)

Question 1

What does the nucleus do?

Answer 1

• contains genetic material that controls the activities of the cell.
• Genetic material is arranged in chromosomes.

Question 2

What does the cytoplasm do?

Answer 2

• gel-like substance where most of the chemicals reactions happen.
• It contains enzymes that control these chemical reactions.

Question 3

What does the mitochondria do?

Answer 3

• where most of the reactions for aerobic respiration takes place.

Question 4

What does respiration do?

Answer 4

• Respiration transfers energy that the cell needs to work.

Question 5

What does the cell membrane do?

Answer 5

• Holds the cell together and controls what goes in and out of the cell.

Question 6

What do the ribosomes do?

Answer 6

• Involved in translation of genetic material in protein synthesis.

Question 7

What does a cell wall do?

Answer 7

• made of cellulose.
• supports the cell and strengthens it.

Question 8

What does the large vacuole do?

Answer 8

• Contains cell sap, a weak solution of sugar and salts.
• Maintains the internal pressure to support the cell.

Question 9

What do the chloroplasts do?

Answer 9

• where photosynthesis occurs, which makes food for the plant.
• Contain a green substance called chlorophyll.

Question 10

What does chromosomal DNA do?

Answer 10

• controls the cell’s activities and replication.
• Floats free in the cytoplasm.

Question 11

What does plasmid DNA do?

Answer 11

• Small loops of extra DNA not part of the chromosome.
• Contain genes for things such as gene resistance and can be passed between bacteria.

Question 12

What does the flagellum do?

Answer 12

• A long, hair-like structure that rotates to make the bacterium move.
• Can be used to move the bacterium away from harmful substances like toxins and towards beneficial things like nutrients and oxygen.

Question 13

Define specialised cells -

Answer 13

Cells that have a structure which makes them adapted to their function.

Question 14

How are egg cells adapted to their function (3 marks)

Answer 14

1) - It contains nutrients in the cytoplasm to feed the embryo.

2) - It has a haploid nucleus (half).

3) - Straight after fertilisation, its membrane changes structure to stop any more sperm getting in.

4) - This makes sure the offspring end up with the right amount of DNA.

Question 15

How are sperm cells adapted to their function (3 marks)

Answer 15

1) - Has a long tail so it can swim to the egg.

2) - Has lots of mitochondria in the middle section to provide energy from respiration needed to swim this distance.

3) - Has an acrosome at the front of the head, where it stores enzymes needed to digest its way through the membrane of the egg cell.

Question 16

How are ciliated epithelial cells adapted to their function? (3 marks)

Answer 16

• Line surfaces of organs.
• Some of them have cilia (hair-like structures) on the top surface of the cell.
• The function of these ciliated epithelial cells is to move substances - the cilia beat to move substances in one direction, along the surface of the tissue.

Question 17

EXAMPLE of ciliated epithelial cells being adapted to their function:

Answer 17

• Lining of the airways contains these.
• These help to move mucus and particles from the air up to the throat so it can be swallowed and doesn’t reach the lungs.

Question 18

How to prepare a microscope (6 marks)

Answer 18

1) - Take a thin slice of the specimen.

2) - Take a clean slide and use a pipette to put one drop of water in the middle of it to secure the specimen in place.

3) - Use tweezers to place the specimen on the slide.

4) Add a drop of stain if the specimen is completely transparent or colourless - this makes the specimen easier to see.

5) - Place a cover slip at one end of the specimen and lower it onto the slide.

6) Press it down gently so no air bubbles are trapped under it. Then, clip the slide onto the stage.

Question 19

How to view a specimen after preparation of the microscope (4 marks)

Answer 19

1) - Select the lowest powered objective lens.

2) - Use the coarse adjustment knob to move the stage up so the slide is just underneath the objective lens. Then, looking down the eyepiece, move the stage downwards until the specimen is nearly in focus.

3) - Adjust the focus with the fine adjustment knob, until you get a clear image.

4) - Position a clear ruler on the stage and use it to measure the diameter of the circular area visible - your Field Of View.

5) - Swap to a higher-powered objective lens if you need to see your specimen with greater magnification.

Question 20

What do enzymes do?

Answer 20

• Reduce the need for high temperatures and they speed up the useful chemical reactions in the body.

Question 21

Catalyst Definition -

Answer 21

• A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction.

Question 22

What is the substrate?

Answer 22

• The molecule being changed in the reaction.

Question 23

The ‘lock and key’ hypothesis:

Answer 23

• Every enzyme has an active site.
• Enzymes only work with one substrate usually. They have a high specificity for their substrate.
• The substrate has to fit into the active site.
• If the substrate’s shape doesn’t match the active site’s shape, then the reaction won’t be catalysed.

Question 24

Define the active site

Answer 24

• the part where an enzyme joins onto its substrate to catalyse the reaction

Question 25

Effect of temperature on enzyme’s rate of reaction:

Answer 25

• A higher temperature increases the rate at first.
• But if it gets too hot, some bonds holding the enzyme together break. This changes the active site’s shape so the substrate not longer fits.
• The enzyme is said to be denatured.

Question 26

Effect of pH on enzymes

Answer 26

• if too high or too low, it can interfere with the bonds holding the enzyme together.
• changes the shape of the active site and denatures the enzyme.
• Optimum is often pH 7

Question 27

Effect of substrate concentration on enzymes

Answer 27

• The higher the substrate concentration, the higher the rate of reaction up to a point because it means that the enzyme is more likely to meet up and react with a substrate molecule.
• After a certain point, all the active sites are full, so adding more substrates makes no difference.

Question 28

What do carbohydrases do?

Answer 28

Convert carbohydrates into simple sugars.

• e.g Starch > Amylaze Enzyme > Maltose

Question 29

What do proteases do?

Answer 29

Convert proteins into amino acids.

• e.g Proteins > Protease Enzymes > Amino Acids

Question 30

What do lipases do?

Answer 30

Convert lipids into fatty acids and glycerol.

• e.g Lipid > Lipase Enzyme > Glycerol + Fatty Acids

Question 31

Test for Sugars -

Answer 31

1) - Benedict’s Reagent.

2) - Add this (blue) to a sample and heat in a 75C water bath. If the test is positive, it will form a coloured precipitate (solid particles).

3) - The higher the concentration of reducing sugar, the further the colour change goes.

• Colours (increasing sugar concentration):
• Blue > Green > Yellow > Orange > Brick Red

Question 32

Test for Proteins

Answer 32

1) - Biuret Test

2) - Add a few drops of potassium hydroxide solution to make the solution alkaline.

3) - add some bright blue copper sulfate.

• IF NO PROTEIN, STAYS BLUE.
• IF PROTEIN, TURNS PURPLE.

Question 33

Test for Lipids

Answer 33

1) - Emulsion Test

2) - Shake the test substance with ethanol for around a minute until it dissolves, then pour the solution into water.

3) - The more lipid there is, the more noticeable the milky colour will be.

Question 34

Test for Starch -

Answer 34

1) - Add iodine.

If starch is present, the sample changes from brown-orange to blue-black.

If starch is not present, it stays brown-orange.

Question 35

Energy In Food Equation (J) -

Answer 35

• Mass of water (g) x Temperature Change of Water (C) x 4.2

Question 36

Energy Per Gram of Food (J/g) =

Answer 36

Energy in food (J) / Mass of Food (g)

Question 37

Diffusion Definition -

Answer 37

• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.

Question 38

Active Transport Definition -

Answer 38

• Active Transport is the movement of particles across a membrane against a concentration gradient (from an area of lower concentration to an area of higher concentration) using energy transferred during respiration.

Question 39

Osmosis Definition -

Answer 39

• Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

Question 40

Explain the process of calorimetry (6 marks)

Answer 40

1) - You need a food that’ll burn easily - something that’s dry e.g, dried beans or pasta, will work best.

2) - Weigh a small amount of the food and then skewer it on a mounted needle.

3) - Next, add a set volume of water to a boiling tube held with a clamp)- this will be used to measure the amount of energy that’s transferred when the food is burnt.

4) Measure the temperature of the water, then set fire to the food using a Bunsen burner flame. Make sure the Bunsen isn’t near the water or it may affect your results.

5) - Immediately hold the burning food under the boiling tube until it goes out. Then relight the food and hold it under the tube - keep doing this until the food won’t catch fire again.

6) - The last thing to do is measure the temperature of the water again.

Question 41

Percentage Change =

Answer 41

((Final Mass - Initial Mass) / (Initial Mass))