IB Biology Paper 1 - Fletcher - Topic 2: Molecular Biology (Possible Final questions)

1. Which of the following are connected by hydrogen bonds?

A. Hydrogen to oxygen within a molecule of water

B. Phosphate to sugar in a DNA molecule

C. Base to sugar in a DNA molecule

D. Hydrogen to oxygen between two different molecules of water

D. Hydrogen to oxygen between two different molecules of water

2. The graph below shows the effect of substrate concentration on enzyme activity. What

conclusion can be drawn about section X of the graph?

A. The enzyme has started to denature and the reaction slows down.

B. The reaction has finished and the substrate has been used up.

C. The enzyme is saturated and is working at its maximum reaction rate.

D. Some of the enzyme has been consumed and the reaction has reached a plateau.

C. The enzyme is saturated and is working at its maximum reaction rate.

3. Which type of molecule is shown in the diagram below?

A. Peptide

B. Carbohydrate

C. Lipid

D. Nucleic acid

A. Peptide

4. The percentage of thymine in the DNA of an organism is approximately 30%. What is

the percentage of guanine?

A. 70%

B. 30%

C. 40%

D. 20%

D. 20%

5. What is denaturation?

A. A structural change of a protein that results in the loss of its biological properties

B. A change in the genetic code of an organism

C. A change in the amino acid sequence of a protein causing a disruption of its 3D

shape

D. The process by which amino acids are broken down and ammonia is released

A. A structural change of a protein that results in the loss of its biological properties

6. How do cells capture the energy released by cell respiration?

A. They store it in molecules of carbon dioxide.

B. They produce glucose.

C. The energy is released as pyruvate.

D. They produce ATP.

D. They produce ATP.

7. What is the source of the oxygen released into the air as a product of photosynthesis?

A. Chlorophyll

B. Carbon dioxide only

C. Water only

D. Both water and carbon dioxide

C. Water only

8. What property of water makes it a good evaporative coolant?

A. High latent heat of evaporation

B. Relatively low boiling point

C. Volatility

D. Transparency

A. High latent heat of evaporation

9. A number of different proteins are involved in nerve function. Which of the following

does not require a membrane protein?

A. Active transport of sodium

B. Diffusion of K+

C. Diffusion of the neurotransmitter across the synapse

D. Binding of the neurotransmitter to the post-synaptic membrane

into the cell

C. Diffusion of the neurotransmitter across the synapse

10.What is the difference between galactose and lactose?

A. Lactose is a disaccharide and galactose is a monosaccharide.

B. Lactose is the product of anaerobic respiration in humans and galactose is the

product of anaerobic respiration in yeast.

C. Lactose is an enzyme and galactose is a hormone.

D. Galactose is a sugar found in milk but lactose is not found in milk.

A. Lactose is a disaccharide and galactose is a monosaccharide

11.Which type of light is least useful for photosynthesis in terrestrial plants?

A. Blue

B. Green

C. White

D. Red

B. Green

12.How many molecules of water are required to completely hydrolyse a polypeptide

made up of 23 amino acids?

A. 11

B. 22

C. 23

D. 44

B. 22

13.Which of the following is part of the process of cellular respiration?

A. Changes in the volume of the thoracic cavity

B. Exchange of gases across the surface of the alveoli

C. Exchange of gases across the surface of capillaries

D. Glycolysis

D. Glycolysis

14.Which variable has the least effect on enzyme activity?

A. Temperature

B. Light intensity

C. pH

D. Substrate concentration

B. Light intensity

15.Which substance in prokaryotes contains sulfur?

A. DNA

B. Phospholipids

C. Proteins

D. Antibiotics

C. Proteins

16.Which describes these molecules correctly?

I. and II. (diagram not included)

A. ribose and amino acid

B. glucose and amino acid

C. ribose and fatty acid

D. glucose and fatty acid

D. glucose and fatty acid

17.What sequence of processes is carried out by the structure labelled X during translation?

A. Combining with an amino acid and then binding to an anticodon

B. Binding to an anticodon and then combining with an amino acid

C. Binding to a codon and then combining with an amino acid

D. Combining with an amino acid and then binding to a codon

D. Combining with an amino acid and then binding to a codon

18.The diagram below shows a biochemical pathway in a yeast cell. Which of the

following correctly identifies a compound in the diagram?

A. I is fat.

B. II is pyruvate.

C. III is lactate.

D. IV is carbon dioxide.

B. II is pyruvate.

19.The following diagram shows a short stretch of DNA. What bases are indicated by labels Y and Z?

Adenine --- (Y)

Cytosine --- (Z)

Y Z

A. thymine adenine

B. thymine guanine

C. uracil guanine

D. uracil adenine

B. thymine guanine

20.A plant is exposed to increasing light intensity from very dim to bright light, while the

carbon dioxide concentration and temperature are kept at an optimum level. What will

happen to the rate of oxygen production?

A. It will increase exponentially.

B. It will remain constant.

C. It will decrease to a minimum level.

D. It will increase to a maximum level.

D. It will increase to a maximum level.

21.In some people, hemoglobin always contains the amino acid valine in place of a

glutamic acid at one position in the protein. What is the cause of this?

A. An error in transcription of the hemoglobin gene

B. An error in translation of the mRNA

C. Lack of glutamic acid in the diet

D. A base substitution in the hemoglobin gene

D. A base substitution in the hemoglobin gene

22.What is a role of sulfur in living organisms?

A. Formation of proteins

B. Formation of carbohydrates

C. Formation of teeth

D. Transmission of nerve impulses

A. Formation of proteins

23.Which molecules form the nucleotide marked in the diagram?

A. phosphate, deoxyribose and nitrogenous base

B. phosphorus, ribose and nitrogenous base

C. phosphorus, deoxyribose and guanosine

D. phosphate, ribose and guanine

A. phosphate, deoxyribose and nitrogenous base

24.Which enzyme catalyzes the elongation of the leading strand?

[Source: image from W K Purves, et al., (2003) Life: The Science of Biology, 4, Sinauer Associates

(www.sinauer.com) and W H Freeman (www.whfreeman.com)]

A. RNA polymerase

B. Helicase

C. DNA polymerase

D. Ligase

C. DNA polymerase

25.Which of the following is a function of cellulose in plants?

A. Storage of fat

B. Formation of mitochondria

C. Storage of energy

D. Formation of cell walls

D. Formation of cell walls

26.Which of the following is the best definition of cell respiration?

A. A process needed to use energy, in the form of ATP, to produce organic compounds

B. A process used to provide oxygen to the atmosphere

C. A controlled release of energy, in the form of ATP, from organic compounds incells

D. A controlled release of energy in the production of food from organic compounds

C. A controlled release of energy, in the form of ATP, from organic compounds incells

27.The graph below shows the effect of temperature on the separation of the strands in

DNA to form single strands. The temperature at which 50% of the DNA is single-stranded is called the melting temperature (TM).

What do the results show?

A. When the temperature reaches 85°C there are no more double-stranded DNA molecules.

B. When the temperature reaches 85°C the DNA strands start separating rapidly.

C. A TM of 85°C means that DNA is not stable at room temperature (25°C).

D. The separation of the DNA strands is directly proportional to the increase in temperature.

B. When the temperature reaches 85°C the DNA strands start separating rapidly.

28.Which diagram best illustrates the interactions between water molecules?

B. (connected by one O and one H)

29.What chemical reaction is taking place when a dipeptide becomes two amino acids?

A. Condensation

B. Hydrolysis

C. Denaturation

D. Polymerization

B. Hydrolysis

30.The base ratios in the DNA and RNA for an onion (Allium cepa) are given below.

Bases A / % G / % C / % T / %

DNA 31.8 18.4 18.2 31.3

Bases A / % G / % C / % U / %

RNA 24.9 29.8 24.7 20.6

What is the reason for the difference between these figures?

A. DNA is only found in the nucleus but RNA is found throughout the cell.

B. DNA is made entirely of double helix but RNA is not.

C. In DNA, bases A and T are complementary but in RNA, bases A and C are

complementary.

D. RNA comes in three forms but DNA only comes in one form.

B. DNA is made entirely of double helix but RNA is not.

31.Which of the following will cause an enzyme to permanently lose its properties?

I. Hydrolysis

II. Freezing to -20°C

III. Dissolving it in water

A. I only

B. II only

C. I and II only

D. I and III only

A. I only

32.What is lactase used for?

A. It is used to make sugar-free milk.

B. It hydrolyses lactose to glucose and fructose.

C. It improves the digestion of milk by some people.

D. It decreases the acidity of the milk.

C. It improves the digestion of milk by some people.

33.How can the rate of photosynthesis of a plant be directly measured?

A. By measuring the rate of oxygen produced

B. By measuring the rate of carbon dioxide produced

C. By measuring the rate of plant growth

D. By measuring the rate of light absorbed

A. By measuring the rate of oxygen produced

34.What is true of the source, products and optimum pH of the lipase found in the human

digestive system?

Source Products Optimum pH

A. salivary glands fatty acids 8

B. stomach starch 2

C. pancreas fatty acids 8

D. liver amino acids 2

C. pancreas fatty acids 8

35.Which diagram represents the polarity of a water molecule?

B O- H+ H+

36.Which of these molecules is a disaccharide?

A. Galactose

B. Sucrose

C. Cellulose

D. Ribose

B. Sucrose (fructose + glucose)

37.What is a codon?

A. A sequence of nucleotides on rRNA that corresponds to an amino acid

B. A sequence of nucleotides on mRNA that corresponds to an amino acid

C. A sequence of nucleotides on tRNA that corresponds to an amino acid

D. A sequence of nucleotides on DNA that corresponds to an amino acid

B. A sequence of nucleotides on mRNA that corresponds to an amino acid

38.What happens as an enzyme becomes denatured?

A. The enzyme works faster.

B. The enzyme works slower.

C. The enzyme can perform a new role.

D. The enzyme can make the reverse reaction proceed faster.

B. The enzyme works slower.

39.What happens during the pathway of glycolysis?

A. Glucose is broken down into pyruvate.

B. Carbon dioxide is produced.

C. More ATP is consumed than is produced.

D. Lactic acid is produced.

A. Glucose is broken down into pyruvate.

40.What is light energy used for during photosynthesis?

A. To produce carbon dioxide

B. To produce water molecules

C. To produce ATP

D. To break down sugar molecules

C. To produce ATP

41.Which molecule is shown below?

A. Glucose

B. Galactose

C. Ribose

D. Sucrose

C. Ribose

42.Blood is a water-based transport medium. Which property of water makes it a good transport medium?

A. High specific heat

B. Transparency

C. Versatility as a solvent

D. It has its greatest density at 4°C

C. Versatility as a solvent

43.What is replicated by a semi-conservative process?

A. Messenger RNA (mRNA) only

B. Messenger RNA (mRNA) and transfer RNA (tRNA) only

C. Messenger RNA (mRNA), transfer RNA (tRNA) and DNA only

D. DNA only

D. DNA only

44.Which of the following processes produces CO2?

I. Glycolysis

II. Alcohol (ethanol) fermentation

III. Lactic acid production

A. I only

B. II only

C. I and II only

D. I, II and III

D. I, II and III

45.Which of the following colours of light is absorbed the most by chlorophyll?

A. Blue

B. Green

C. Yellow

D. Orange

A. Blue

46.Which of the following chemical elements are part of biochemical molecules in living

organisms?

A. nitrogen, sulfur, phosphorus and iron

B. lead, oxygen, carbon and phosphorus

C. helium, carbon, sulfur and nitrogen

D. silicon, helium, oxygen and iron

A. nitrogen, sulfur, phosphorus and iron

47.Which of the following is an organic compound made by all plants?

A. Carbon dioxide

B. DNA

C. Lactose

D. Oxygen

D. Oxygen

48.Which of the following graphs shows the relationship between substrate concentration

and enzyme activity with a fixed concentration of enzyme?

C. (exponential rise)

49.Oxygen is produced during photosynthesis. What is the source of this oxygen inside the

plant?

A. Air spaces in the leaf

B. Carbon dioxide

C. Glucose

D. Water

D. Water

50.Which of the following chemical elements are part of biochemical molecules in living organisms?

A. nitrogen, sulfur, phosphorus and iron

B. lead, oxygen, carbon and phosphorus

C. helium, carbon, sulfur and nitrogen

D. silicon, helium, oxygen and iron

A. nitrogen, sulfur, phosphorus and iron

51.Carbon, hydrogen, nitrogen and sulphur are elements found in living cells. Which is the least common?

A. Carbon

B. Hydrogen

C. Nitrogen

D. Sulphur

D. Sulphur

52.Which of the following terms correctly describe the molecule below?

I. Monosaccharide

II. Ribose

III. Carbohydrate

A. I only

B. I and III only

C. II and III only

D. I, II and III

B. I and III only

53.A certain gene in a bacterium codes for a polypeptide that is 120 amino acids long.

How many nucleotides are needed in the mRNA to code for this polypeptide?

A. 30

B. 40

C. 360

D. 480

C. 360 (120*3)

54.What enzyme is used in transcription but not in translation?

A. DNA polymerase

B. Helicase

C. Protease

D. RNA polymerase

A. DNA polymerase

55.Which two colours of light does chlorophyll absorb most?

A. Red and yellow

B. Green and blue

C. Red and green

D. Red and blue

D. Red and blue

1 (a) State one example of a fibrous protein and one example of a globular protein.

Fibrous protein:

Globular protein:

Fibrous protein:

Collagen

Globular protein:

hemoglobin

1 (b) Compare the structure of fibrous and globular proteins.

both are polypeptides

globular proteins have tertiary structure

fibrous proteins do not (may have extended secondary structure);

globular proteins are rounded in shape

fibrous proteins are elongated;

globular proteins are (generally) soluble

fibrous tend to be insoluble;

1 (c) Amino acid polarity is an important factor in determining the functions of proteins.

Explain the importance of polar and non-polar amino acids in membrane proteins.

polar amino acids are soluble;

non-polar amino acids are soluble;

polar amino acids strongly hydrophilic and non-polar amino acids are hydrophobic;

(help to) retain protein in position in the membrane;

polar amino acids form hydrophilic channels in membranes;

transmembrane proteins have polar amino acids on either side of the membrane;

4. (a) Outline the bonding between DNA nucleotides.

hydrogen bonds between nucleotides of complementary bases;

covalent bonds between nucleotides between sugar/deoxyribose and phosphate;

4. (b) Explain how chemical bonding between water molecules makes water a valuable coolant in living organisms.

hydrogen bonding between water molecules;

breaking (hydrogen bonds) removes heat;

hydrogen bonds must break when water evaporates/vaporizes;

4. (c) Describe the movement of water across membranes.

osmosis / moves passively;

from regions of low solute/high water potential/concentration to

high solute concentration / low water potential/concentration;

passes through protein channels/aquaporins/selectively-permeable membrane;

4. (d) State the role of water in photosynthesis.

water molecules undergo photolysis/are split by light energy;

forms oxygen as a by-product;

hydrogen helps power the fixation of carbon (into organic molecules);

5. (a) State two functions of proteins, giving a named example of each.

structure—collagen;

transport—hemoglobin;

enzymes/biological catalyst —amylase/protease/lipase/catalase;

defence/immunity — immunoglobin/antibody;

movement — actin/myosin;

synthesis — ligase/DNA polymerase;

hormonal communication — insulin/luteinizing hormone; MUST be

proteinaceous

food stores — casein in milk;

pigments—opsin;

5. (b) Explain the significance of polar and non-polar amino acids.

polar amino acids have hydrophilic R groups, non-polar have hydrophobic R groups;

non-polar amino acids in centre of water-soluble proteins stabilise their structure;

non-polar amino acids cause proteins to remain embedded in membrane;

polar amino acids on surface of proteins make them water-soluble;

polar amino acids create hydrophilic channels/protein pores in membranes;

enzyme active site specificity depends on amino acids present/polar and non-polar amino acids can play a role in substrate interactions at the active site;

10. (a) Define active site.

site on surface/portion of the enzyme/protein to which the substrate binds

10. (b) Explain enzyme-substrate specificity.

enzymes fit together with substrates similar to a lock and key;

active site has shape that gives specificity;

enzymes catalyze a reaction with a specific substrate;

example of named enzyme and its substrate;

substrate held precisely in (optimum) position to make/break bonds/carry

out reaction / chemical interaction occurs between enzyme and substrate;

11. (a) State the property of stem cells that makes them useful in medical treatment.

has the ability to differentiate (into specialized tissue)

11. (b) Explain how multicellular organisms develop specialized tissues.

only some genes are expressed in each cell type/tissue;

tissues therefore develop differently/become differentiated;

example of differentiated cell and the function of tissues;

11. (c) Outline some of the outcomes of the sequencing of the human genome.

knowledge of location of human genes / position of human genes on

chromosomes;

knowledge of number of genes/interaction of genes / understanding

the mechanism of mutations;

evolutionary relationships between humans and other animals;

discovery of proteins / understanding protein function / detection

of genetic disease;

leads to the development of medical treatment/enhanced research

techniques;

knowledge of the base sequence of genes/study of variation within genome;

12. (b) State one difference between oxidation and reduction.

oxidation is addition of oxygen while reduction is removal;

oxidation is removal of H+, reduction is addition;

oxidation is loss of electrons, reduction is gain;

13. (a) State the type of bonds that

(i) connect base pairs in a DNA molecule.

(ii) link DNA nucleotides into a single strand.

(i) hydrogen

(ii) covalent / phosphodiester linkage

13. (b) Distinguish between DNA and RNA nucleotides by giving two differences in the chemical structure of the molecules.

DNA has deoxyribose, RNA has ribose;

DNA has base T/thymine, RNA has base U/uracil;

Do not accept double or single strands as chemical structure.

13. (c) Explain the role of transfer RNA (tRNA) in the process of translation.

tRNA attaches to (specific) amino acid;

tRNA (with amino acid) moves to the ribosome;

anticodon of tRNA binds with codon of mRNA;