b1.2 what happens in cells?

Question 1

what does DNA stand for?

Answer 1

deoxyribonucleic acid

Question 2

what is DNA?

Answer 2

a polymer

Question 3

how many strands does DNA have?

Answer 3

two, forming a double helix

Question 4

what is DNA made up of?

Answer 4

nucleotides

Question 5

what makes up a nucleotide?

Answer 5

a sugar, a phosphate group and a base

Question 6

what are the 4 bases?

Answer 6

A: adenine
T: thymine
G: guanine
C: cytosine

Question 7

what is the function of DNA?

Answer 7

it contains the genetic material that determines the characteristics of an organism

Question 8

what are the complementary bases?

Answer 8

C-G
A-T

Question 9

what does a group of three bases code for?

Answer 9

an amino acid

Question 10

what are chromosomes?

Answer 10

structures made up of long molecules of DNA

Question 11

what are the two stages of protein synthesis

Answer 11

transcription and translation

Question 12

what is a gene?

Answer 12

a section of DNA that codes for a protein

Question 13

describe what happens during transcription

Answer 13

1. In the nucleus, the two DNA strand unzip around the gene to make it accessible.
2. DNA is used as a template to make the mRNA. base pairing ensures mRNA nucleotides match to their complementary bases.

Question 14

describe what happens during translation

Answer 14

1. the mRNA moves out of the nucleus to the cytoplasm and joins with ribosomes
2. amino acids join with matching triplet codes on the mRNA, in the correct order. this makes the protein.
3. the amino acids are brought to the ribosome by tRNA.
4. when the chain is complete, the protein forms a unique 3D structure

Question 15

what are enzymes?

Answer 15

biological catalysts that speed up the rate of chemical reactions without being used up or changed

Question 16

how do enzymes work?

Answer 16

• every enzyme has a uniquely shaped active site where the substrate binds onto it (the substrate is complementary to the shape of the active site)
• once bound, the reaction takes place

Question 17

how are enzymes necessary to life regarding metabolic reactions?

Answer 17

enzymes allow metabolic reactions to occur at a rate that can sustain life

Question 18

what are 3 factors that affect enzyme reactions?

Answer 18

temperature
pH
concentration

Question 19

how does temperature affect enzymes?

Answer 19

• each enzyme has an optimum temperature when the reaction goes fastest (around 37 degrees C)
• the rate of reaction increases with an
  increase in temperature
• when the temperature becomes too hot, bonds in the enzymes structure begin to break and change the shape of the active site
• the enzyme denatures and no longer works

Question 20

how does pH affect enzymes?

Answer 20

• if the pH is too high or too low it interferes with the bonds holding the enzyme together: changing the shape of the active site and can denature the enzyme
• optimum pH is usually 7

Question 21

how does enzyme concentration affect the rate of reaction?

Answer 21

• increasing the concentration increases the rate because the more enzyme molecules there are, the more likely a substrate molecule will join
• if the concentration is too high, the enzyme will no longer work