B1.2

Question 1

What does DNA stand for?

Answer 1

Deoxyribonucleic acid.

Question 2

What is the structure of a DNA molecule?

Answer 2

DNA is a double helix made from two strands twisted around each other.

Question 3

Is DNA a monomer or a polymer? Explain.

Answer 3

DNA is a polymer — it is made of many repeating units called nucleotides.

Question 4

What are the three components of a DNA nucleotide?

Answer 4

1) One sugar molecule

2) One phosphate group

3) One organic base (A, C, G, or T)

Question 5

What forms the ‘backbone’ of a DNA molecule?

Answer 5

The sugar and phosphate group of each nucleotide.

Question 6

What are the four organic bases in DNA?

Answer 6

Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).

Question 7

What is complementary base pairing in DNA?

Answer 7

A always pairs with T, and C always pairs with G.

Question 8

How many bases code for a single amino acid?

Answer 8

A group of three bases codes for one amino acid.

Question 9

What happens when many amino acids join together?

Answer 9

They form a protein.

Question 10

What are chromosomes made of?

Answer 10

Chromosomes are structures made from long molecules of DNA.

Question 11

Why can’t DNA leave the nucleus to make proteins?

Answer 11

DNA is too large to leave the nucleus.

Question 12

What is the purpose of protein synthesis?

Answer 12

To copy and transport genetic information from the DNA to the ribosomes to make proteins.

Question 13

What happens first in protein synthesis?

Answer 13

The DNA helix is untwisted and unzipped.

Question 14

What matches to the unzipped DNA bases?

Answer 14

Messenger RNA (mRNA) nucleotides match to their complementary DNA bases

Question 15

What is the result of the mRNA nucleotides joining together?

Answer 15

They form a new strand called the template strand.

Question 16

What is the name of the process that forms the mRNA template strand?

Answer 16

Transcription

Question 17

What happens to the template strand after transcription?

Answer 17

It moves out of the nucleus into the cytoplasm.

Question 18

Where does the mRNA strand go in the cytoplasm?

Answer 18

To structures called ribosomes.

Question 19

How is the mRNA read at the ribosome?

Answer 19

In groups of three bases (codons), each coding for one amino acid.

Question 20

What is the name of the process where the mRNA is read to build a protein?

Answer 20

Translation

Question 21

What brings amino acids to the ribosome?

Answer 21

Carrier molecules called tRNA

Question 22

What happens to the amino acids at the ribosome?

Answer 22

They are joined together to form a protein.

Question 23

What determines which protein is produced?

Answer 23

The sequence of triplet base codes (codons) on the mRNA.

Question 24

What happens after the protein chain is complete?

Answer 24

The protein folds to form a unique 3D structure.

Question 25

What are enzymes?

Answer 25

Enzymes are biological catalysts — substances that speed up chemical reactions without being used up.

Question 26

What are enzymes made of?

Answer 26

Enzymes are protein molecules.

Question 27

Why is the shape of an enzyme important?

Answer 27

Each enzyme has a uniquely shaped active site that fits a specific substrate.

Question 28

What is the lock and key hypothesis?

Answer 28

The substrate fits into the enzyme’s active site because their shapes are complementary, forming an enzyme-substrate complex.

Question 29

What happens after the enzyme-substrate complex forms?

Answer 29

The reaction occurs and the products are released from the enzyme’s surface.

Question 30

What is the formula to calculate the rate of a reaction?

Answer 30

Rate = change in concentration ÷ time

Question 31

What is the optimum temperature for most enzymes?

Answer 31

Around 37°C (body temperature).

Question 32

How does temperature affect enzyme activity up to the optimum?

Answer 32

Reaction rate increases with temperature up to the optimum.

Question 33

What happens to enzymes at high temperatures above the optimum?

Answer 33

The enzyme’s structure breaks down — the active site changes shape.

Question 34

What is it called when the enzyme’s shape changes and it stops working?

Answer 34

The enzyme is denatured.

Question 35

What is the optimum pH for most enzymes?

Answer 35

pH 7, but some enzymes (like in the stomach) have a lower optimum pH

Question 36

What happens if the pH is too high or too low?

Answer 36

The forces holding the amino acid chains are affected, changing the active site’s shape.

Question 37

What is the result of an enzyme’s active site changing shape due to pH?

Answer 37

The enzyme becomes denatured and can no longer function.

Question 38

What happens to the rate of reaction as substrate concentration increases?

Answer 38

It increases because there are more substrate molecules to collide with enzymes.

Question 39

Why does increasing substrate concentration eventually stop affecting the rate?

Answer 39

All enzyme active sites become full, so adding more substrate has no further effect.

Question 40

How does enzyme concentration affect the reaction rate at first?

Answer 40

Increasing enzyme concentration increases the reaction rate.

Question 41

Why does the rate stop increasing after a certain point?

Answer 41

There are not enough substrate molecules to react with all the enzyme molecules.