Topic 1 - Key Concepts in Biology

Question 1

What are all living things made up of?

Answer 1

Cells

Question 2

What are the two types of cell?

Answer 2

• Eukaryotic (Complex, animal and plant cells)

- Prokaryotic (Simple, bacteria)

Question 3

What is a prokaryote?

Answer 3

A single-celled organism

Question 4

What do both animal and plant cells contain?

Answer 4

• Nucleus
• Cytoplasm
• Cell membrane
• Mitochondria
• Ribosomes

Question 5

What extra subcellular structures do plant cells contain?

Answer 5

• Cell wall
• Vacuole
• Chloroplasts

Question 6

What is the main structure that a bacterial cell does not contain?

Answer 6

Nucleus

Question 7

What is a specialised cell?

Answer 7

A cell with a specialised purpose

Question 8

Name three specialised cells, and give reasoning:

Answer 8

• Sperm Cell: Many mitochondria to swim, enzyme in head, has a flagellum
• Egg Cell: Nutrients in cytoplasm
• Ciliated Epithelial Cell: Have cilia on the ends

Question 9

What apparatus do we use to study cells?

Answer 9

Microscopes

Question 10

What is the most powerful microscope, and what is its magnification power?

Answer 10

Electron microscope - 2000000x

Question 11

What is the equation for total magnification?

Answer 11

Total magnification = Eyepiece lens magnification x Objective lens magnification

Question 12

What is the equation for magnification if you don’t know the lens magnifications?

Answer 12

Magnification = Image size / Real size

Question 13

What is an enzyme?

Answer 13

A catalyst produced by living things

Question 14

Why does an enzyme only catalyse one reaction?

Answer 14

Because the active site is of a shape that only fits a particular substrate

Question 15

What 3 factors affect enzyme-catalysed rates of reaction, and why?

Answer 15

• Temperature: High temp. causes denaturing
• pH: Low and high pH cause enzymes to denature
• Substrate conc.: More substrates means more active sites are filled

Question 16

What break down big molecules such as carbohydrates, proteins and lipids?

Answer 16

Catalysts

Question 17

Name the three conversions of big molecules, including the enzyme used:

Answer 17

Starch + Amylase = Maltose
Protein + Protease = Amino Acids
Lipid + Lipase = Glycerol and fatty acids

Question 18

What is the test for sugars?

Answer 18

• Add Benedict’s reagent (blue) to a sample
• Heat to 75 degrees Celsius
• If the test is positive, a precipitate either yellow, orange or red in colour will form

Question 19

What is the test for starch?

Answer 19

• Add iodine to the test sample

- If the test is positive, the sample changes from browny-orange to blue-black.

Question 20

What is the test for lipids?

Answer 20

• Add ethanol to the test substance and shake
• When it dissolves, add it to water
• If the test is positive, a milky coloured precipitate will rise above the water

Question 21

What is the test for proteins?

Answer 21

• Add potassium hydroxide to the solution
• Add copper II sulfate (blue)
• If the test is positive, the colour will change from blue to purple

Question 22

How do you test the number of calories in a food?

Answer 22

Calorimetry

Question 23

What are the steps for carrying out a calorimetry?

Answer 23

• Weigh the sample
• Measure a set volume of water
• Measure the temperature
• Heat the sample until it burns
• Hold the burning food under the water
• Measure the change in temperature

Question 24

How do you calculate the energy in food (J)?

Answer 24

Energy in food = Mass of water x Temperature change x 4.2

Question 25

How do you calculate energy per gram of food?

Answer 25

Energy per gram of food = Energy in food / Mass of food

Question 26

What are the three ways substances can move?

Answer 26

- Diffusion - Osmosis - Active Transport

Question 27

Define diffusion:

Answer 27

The net movement of particles from an area of high concentration to low concentration.

Question 28

Define osmosis:

Answer 28

The net movement of water molecules across a partially permeable membrane from an area of high concentration to low concentration.

Question 29

Define active transport:

Answer 29

The net movement of particles across a membrane AGAINST the concentration gradient. It is the only transportation method that requires energy to take place.

Question 30

What are the steps in an experiment to investigate osmosis?

Answer 30

- Prepare sucrose solutions of different concentrations - Cut a potato into equal size and weight pieces - Put the potato pieces into the sucrose solutions (e piece per solution) - Wait for at least 40 mins - Re-weigh the potatoes

Question 31

What does the graph for the osmosis practical look like? Describe what each section shows:

Answer 31

It is a curve moving down and right - Above x-axis = Higher conc in solution than potato - On x-axis = Concentrations are equal - Below x-axis = Higher conc in potato than soution