Key Concepts in Biology

Question 1

Describe how sperm cells are adapted to their function. ( 4 points)

Answer 1

• haploid nucleus (contains the genes- 23 chromosomes)
• long tail & streamlined to aid swimming
• top of head has digestive enzymes to help break down the outer membrane of the egg cell
• lots of mitochondria to supply the energy to allow the sperm to move

Question 2

Describe how egg cells are adapted to their function. (3 points)

Answer 2

• surrounded by special cell membrane which can only accept one sperm cell
• lots of mitochondria to provide energy for the developing embryo
• large size and cytoplasm allow quick repeated division as the embryo grows

Question 3

Describe how ciliated epithelial cells are adapted to their function. (1 point)

Answer 3

• long hair like structures called cilia which trap bacteria on their sticky mucus surface and killed by stomach acid

Question 4

Identify the common parts of bacteria. (6 points)

Answer 4

• cytoplasm
• cell membrane
• cell wall
• chromosomal DNA (circular)
• plasmids
• flagella

Question 5

Describe the function of the cytoplasm

Answer 5

liquid substance where chemical reactions occur, contain enzymes and organelles are found in it

Question 6

Describe the function of the cell membrane

Answer 6

controls what enters and leaves the cell

Question 7

Describe the function of the cell wall

Answer 7

provides structure to the cell and is made from cellulose

Question 8

Describe the function of the chromosomal DNA

Answer 8

have no nucleus, this floats in cytoplasm

Question 9

Describe the function of the plasmids

Answer 9

small rings of DNA, code for extra genes

Question 10

Describe the function of the flagella

Answer 10

long, thin tail that allows them to move

Question 11

Describe why bacteria are classified as being prokaryotic.

Answer 11

small and lack membrane-bound nuclei

Question 12

Definition of an enzyme

Answer 12

biological catalyst that speeds up the rate of reaction without being used up

Question 13

Differences between prokaryotic and eukaryotic cells

Answer 13

prokaryotes don’t have
- a nucleus

prokaryotes have:

• chromosomal DNA
• flagellum
• cell wall

Question 14

Give examples of enzymes (3 points)

Answer 14

• carbohydrases-> amylase breaks down into maltose
• lipases
• proteases-> pepsin

Question 15

What do carbohydrases do?

Answer 15

convert carbohydrates into simple sugars

Question 16

what do proteases do?

Answer 16

Convert proteins into amino acids

Question 17

what do lipases do?

Answer 17

convert lipids (fats) into fatty acids and glycerol

Question 18

where is amylase found?

Answer 18

salivary glands, pancreas and small intestine

Question 19

where is pepsin found?

Answer 19

produced in the stomach

Question 20

where is lipase produce?

Answer 20

in the small intestine and pancreas

Question 21

Explain why catalysis by enzymes is important for life processes

Answer 21

to speed up reactions

Question 22

Describe how to test for starch in food.

Answer 22

iodine reaction -> orange to blue black

Question 23

Describe how to test for reducing sugars in food.

Answer 23

Benedicts solution-> blue to reddish brown

Question 24

State what enzyme specificity means

Answer 24

lock and key hypothesis

Question 25

an enzyme’s action is due to its…

Answer 25

active site.

Question 26

Stages of the lock and key hypothesis

Answer 26

Substrate diffuses into the active site and binds to it – the substrate must be a specific shape to fit into the enzyme
The substrate forms temporary bonds with the AA’s in the enzyme to produce an ENZYME – SUBSTRATE COMPLEX
The reaction takes place and the bonds in the substrate are broken – in this case, the larger molecule has been broken down into smaller molecules. An ENZYME – PRODUCT COMPLEX has formed
The products unbind from the active site and diffuses out
The enzyme is ready to be used again

Question 27

Definition of an enzyme

Answer 27

a biological catalyst

Question 28

How do enzymes become denatured?

Answer 28

Temperature, pH

Question 29

Describe the effect of substrate concentration on enzyme activity.

Answer 29

as substrate conc increases, rate of reaction increases to a saturation point

Question 30

Describe the effect of pH on enzyme activity.

Answer 30

too high or to low will affect amino acid chains and denature the protein

Question 31

What is diffusion

Answer 31

a form of passive transport- movement of high conc to low

Question 32

What is osmosis

Answer 32

a form of passive transport- movement of high conc to low- only applies to water across a selectively permeable membrane

Question 33

what is active transport

Answer 33

a form of transport that does require energy

Question 34

Describe what effect a mutation could have on the action of an enzyme.

Answer 34

a mutation is a change in a gene sequence, which changed the amino acid sequence, changes the shape of the protein/active site, preventing binding

Question 35

Explain the role of the active site of an enzyme.

Answer 35

specific shape, bind to substratem catalyse reactions, lock and key hypothesis

Question 36

Explain why phenolphthalein turns colourless when lipase breaks down the lipids in milk.

Answer 36

fatty acids are formed when the lipids are broken down

by lipase,and fatty acids are acidic (so the pH decreases)

Question 37

Explain why the activity of lipase changes above a temperature of 40°C.

Answer 37

an increase in temperature above 40 °C causes changes
in the shape of the active site of the enzyme.therefore the enzyme becomes denatured and no
longer functions

Question 38

Explain why enzymes can only catalyse specific reactions.

Answer 38

the active sit of an enzyme has a specific shape because of the order of amino acids, the substrate must have a shape which is complementary to the active site

Question 39

Describe what happens to the molecule produced by transcription before it is translated.

Answer 39

leaves the nucleus, through the nuclear membrane and attached to ribosome

Question 40

Explain how the lock and key hypothesis models how enzymes work.

Answer 40

 (enzyme and substrate have) complementary shapes
 substrate fits into enzyme / enzyme substrate complex formed
 reference to active site
 enzymes break (chemical) bonds / form chemical bonds / (causes) reaction to occur / make products
 Idea of products leaving enzyme (so that enzyme can be used again)

Question 41

Describe how named factors affect the rate of enzyme-catalysed reactions.

Answer 41

A description to include some of the following points Temperature
 (temperature) too low – not enough energy to make reactions occur (fast enough)
 reference to optimum temperature
 optimum for most (humans) - 37oC
 over 37oC changes enzyme shape / changes active site
shape of enzyme
 therefore rate of reaction decreases / stops
 enzymes denatured (if temperature too high)
pH
 optimum pH – around 7.3 / 6 to 8 for most enzymes
 specific optimum quoted eg pepsin – pH 2 to 3
 pH either side of optimum – changes the shape of the
enzyme / shape of the active site
 therefore rate of reaction decreases / stops
 enzymes denatured (if pH too high / too low)
substrate / enzyme concentration
 higher concentrations faster reactions
 due to more collisions
 until maximum rate reached / all enzymes being used