Topic 1

Question 1

What are the subcellular structures of animal cells and briefly describe their roles

Answer 1

1. Nucleus - contains GM of cell and controls the activites of the cell
2. Cytoplasm - where chemical reactions take place
3. Cell membrane - controls what goes in an out of cell and holds cell together
4. Mitochondria - where most respiration reactions take place
5. Ribosomes - involved in protein synthesis

Question 2

What are the 3 extra subcellular structures in plant cells and briefly describe their roles

Answer 2

1. Rigid cell wall - supports and strengthens cell
2. Large vacuole - contains cell sap and maintains internal pressure to support cell
3. Chloroplasts - where photosynthesis occurs (contains chlorophyll)

Question 3

What are the 5 subcellular structures of bacteria cells

Answer 3

1. Chromosomal DNA (lying free in cytoplasm)
2. Ribosomes
3. Cell membrane
4. Plasmid DNA (can be passed between bacteria)
5. Flagellum

Question 4

How are sperm cells adapted to their function?

Answer 4

1. Long tail to swim to egg
2. Lots of mitochondria in middle section to provide energy for distance
3. Acrosome with enzymes in it to digest into membrane of the egg
4. Contains a haploid nucleus

Question 5

How are egg cells adapted to their function?

Answer 5

1. Have nutrients in cytoplasm to feed the embryo
2. Has a haploid nucleus
3. After fertilisation, membrane changes shape to stop sperm getting in. This ensures offspring gets right amount of DNA

Question 6

How are ciliated epithelial cells adapted to their function?

Answer 6

They have cilia on the top surface of the cell to move substances along the surface of a tissue. e.g. to move mucus up to throat and away from lungs

Question 7

Why are electron microscopes useful? (compare them to light microscopes)

Answer 7

• They have a higher magnification and resolution than light microscopes, so they allow us to see things in more detail. e.g. like the internal structure of mitochondria and chloroplasts
• This has allows us to have a great understanding of how cells work and the role of subcellular structures

Question 8

rank the 4 unit sizes in order of smallest to biggest? (starting from picometer)

Answer 8

Picometre, nanometre, micrometre, millimetre

Question 9

Recall the 2 magnification equations

Answer 9

Magnification = image/actual

Magnification = eyepiece*objective

Question 10

Give 2 features of an enzyme (hint: active site and specificity)

Answer 10

1. They have an active site, which is joins onto a substrate to catalyse a reaction
2. They have a high specificity for their substrate

Question 11

What three factors affect the rate of a reaction

Answer 11

1. Substrate concentration (to an extent)
2. pH
3. Temperature

Question 12

How does an enzyme denature? (what happens in the enzyme that causes it to denature)

Answer 12

Some of the bonds holding an enzyme together break. This changes the shape of the active site, so that a substrat will no longer fit. (enzyme therefore denatures)

Question 13

Give the eqation to calculate the rate of a reaction

Answer 13

rate = 1000/time

Question 14

Describe the function of the three different types of enzymes and give an example for carbohydrases:

• Carbohydrase
• Protease
• Lipase

Answer 14

1. Carbohydrases - converts carbs into simple sugars e.g amylase breaks down starch into maltose and other sugars
2. Proteases - convert proteins into amino acids
3. Lipases - convert lipids into glycerol and fatty acids

Question 15

Why are enzymes useful for the body?

Answer 15

They help break down molecules that are too big to pass through our digestive system, so that they can be absorbed into the bloodstream and pass into cells, in order to be used by the body

Question 16

Why are enzymes useful for plants?

Answer 16

When plants need energy, enzymes break down starch into smaller molecules. These can then be respired to transfer energy to be used by the cells

Question 17

Describe the test for sugars?

Answer 17

(benedicts reagent test)

Add benedicts to a sample and hear it in a water bath at 75 degrees. Coloured precipitate will form if sugars are present

Blue Giants Yell On Buses (colours)

Question 18

Descrie the test for starch

Answer 18

Add iodine to a sample.

• if it turns blue/black, then starch is present
• if it remains browny-orange, theres no starch present

Question 19

Describe tahe test for lipids

Answer 19

Emulsion test

• Shake the test substance with ethanol for a min till it dissolves, pour solution in water
• If lipids are present, they will precipitate out of the liquid and show as a milky emulsion

Question 20

Decribe the test for proteins

Answer 20

Biuret test

1. Add a few drops of potassium hydroxide solution to make solution alkaline
2. Then add copper sulfate solution (blue)
3. • If proteins are present , solution turns purple
   • If proteins are not present, solution remains blue

Question 21

Describe the calorimetry experiment

Answer 21

1. Weigh food and place onto mounted neede
2. Measure set volme of water into a boiling tube and measure temp of water before experiment
3. light food under the boiling tube and keep relighting until food wont relight anymore
4. Measure temp of water in the end

Question 22

What are the two equations to calculate the amount of energy in food

Answer 22

1. Energy in food = mass of water * temp change * 4.2
2. Energy per gram of food = energy in food/mass of food

(1 cm^3 is equal to 1g of water)

Question 23

Define active transport

Answer 23

The movement of particles from an area of low to high concentration) against a concentration gradient, which uses energy transferred by respiration

Question 24

Give an example of active transport

Answer 24

When theres a lower conc of nutrients in the gut than in the blood, the nutrients move into the blood. This is essential to stop us starving

Question 25

What must you keep the same in the potato experiment?

Answer 25

- The type of potatoes - the age of the potatoes - the volume of solution

Question 26

What is the equation to calculate percentage change?

Answer 26

Percentage change = ((final mass - initial mass)/initial mass) * 100

Question 27

Describe the experiment to investigate the effect of pH on enzyme activity

Answer 27

1. Heat water to 35 degrees 2. Add 3cm^3 of buffer solution with a specific pH and 3cm^3 of amylase solution to a test tube. Put boiling tue into beaker and wait for 5 minutes 3. Add 3cm^3 of starch to the boiling tube and mix sultions before starting a stopclock 4. Drop solution into wells of a spotting tiles with iodine, and record how long it takes for the amylase to break down the starch. (you'll know when the colour of the iodine remains brown again)