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A Level H1 Biology Practice Paper 1

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TuitionGoWhere Practice Paper - Biology H1 A-Level

TuitionGoWhere Secondary School (AI)

Subject: Biology H1
Level: A-Level
Paper: PRACTICE Paper 2
Duration: 2 hours
Total Marks: 80 marks

Name: _________________ Class: _________ Date: _________

Instructions to Candidates

Answer ALL questions
Write your answers in the spaces provided
Show all working for calculation questions
Use appropriate biological terminology throughout
Refer to figures and tables where indicated
Quality of written communication will be assessed

Section A: Structured Response Questions [60 marks]

Question 1 [12 marks]

Fig. 1.1 shows the structure of a generalized animal cell as seen under an electron microscope.

[THIS IS FIGURE: Diagram of an animal cell with structures labeled A through F]

(a) Name the structures labeled A, C, and E. [3]

A: _________________________________________________

C: _________________________________________________

E: _________________________________________________

(b) State two functions of structure B in the cell. [2]

(i) _________________________________________________

(ii) _________________________________________________

(d) Describe the role of structure F in protein synthesis. [4]

Question 2 [15 marks]

Fig. 2.1 shows the cell cycle of a typical mammalian cell.

[THIS IS FIGURE: Circular diagram showing cell cycle phases labeled with letters P, Q, R, S, T]

(a) (i) With reference to Fig. 2.1, identify the phase where DNA replication occurs. [1]

(ii) State what happens during phase T. [2]

(b) A student added radioactive thymine to cells at the beginning of phase Q. Explain in which phase the radioactivity would first be observed in the nucleus. [3]

[THIS IS FIGURE: Graph showing DNA content vs time with points labeled 1-4]

Explain the changes in DNA content from point 1 to point 4. [6]

Point 1 to 2: _________________________________________________

Point 2 to 3: _________________________________________________

Point 3 to 4: _________________________________________________

(d) State three differences between mitosis and meiosis. [3]

(i) _________________________________________________

(ii) _________________________________________________

(iii) _________________________________________________

Question 3 [18 marks]

A student investigated the effect of different concentrations of sucrose solution on potato tissue.

The student cut potato cylinders of equal size and placed them in different concentrations of sucrose solution for 2 hours. The results are shown in Table 3.1.

Table 3.1

Sucrose concentration (mol dm⁻³)	Initial mass (g)	Final mass (g)	Change in mass (g)	Percentage change in mass (%)
0.0	2.45	2.89	+0.44	+18.0
0.2	2.52	2.71	+0.19	+7.5
0.4	2.48	2.48	0.00	0.0
0.6	2.51	2.31	-0.20	-8.0
0.8	2.46	2.17	-0.29	-11.8
1.0	2.49	2.11	-0.38	-15.3

(a) Name the process responsible for the change in mass of the potato cylinders. [1]

(b) Explain why the potato cylinders gained mass in distilled water (0.0 mol dm⁻³). [3]

(ii) Explain how you determined this from the results. [2]

(d) Predict the percentage change in mass if the potato cylinders were placed in 1.2 mol dm⁻³ sucrose solution. Explain your prediction. [3]

(e) Describe how you would modify this experiment to investigate the effect of temperature on the rate of water movement. [4]

(f) State two variables that should be controlled in this investigation. [2]

(i) _________________________________________________

(ii) _________________________________________________

(g) Suggest two sources of error in this experiment and how they could be reduced. [2]

(i) _________________________________________________

(ii) _________________________________________________

Question 4 [15 marks]

Fig. 4.1 shows the structure of an enzyme and its substrate.

[THIS IS FIGURE: Diagram showing enzyme with active site and substrate molecule]

(a) Explain how enzymes increase the rate of biochemical reactions. [4]

(b) Fig. 4.2 shows the effect of pH on the activity of two different enzymes, A and B.

[THIS IS FIGURE: Graph showing enzyme activity vs pH for enzymes A and B, with different optimal pH values]

(i) State the optimum pH for enzyme A and enzyme B. [2]

Enzyme A: _________________________________________________

Enzyme B: _________________________________________________

(ii) Suggest where in the human body enzyme A and enzyme B might be found. Give reasons for your answers. [4]

Enzyme A: _________________________________________________

Reason: _________________________________________________

Enzyme B: _________________________________________________

Reason: _________________________________________________

(d) State two other factors that affect enzyme activity. [2]

(i) _________________________________________________

(ii) _________________________________________________

Section B: Extended Response Question [20 marks]

Question 5 [20 marks]

(a) Describe the structure and properties of biological membranes and explain how they control the movement of substances into and out of cells. [12]

(b) Discuss the importance of membrane transport processes in maintaining cellular homeostasis. [8]

END OF PAPER

Answers

TuitionGoWhere Practice Paper - Biology H1 A-Level - Mark Scheme

Total: 80 marks

Section A: Structured Response Questions [60 marks]

Question 1 [12 marks]

(a) Name the structures labeled A, C, and E. [3]

A: Cell/plasma membrane [1]
C: Mitochondrion/mitochondria [1]
E: Nucleus [1]

(b) State two functions of structure B in the cell. [2] [Structure B = Endoplasmic reticulum]

Protein synthesis (if rough ER) [1]
Lipid synthesis [1]
Transport of materials through the cell [1]
Calcium storage [1] [Accept any 2 valid functions]

Folding increases surface area [1]
More space for electron transport chain/ATP synthase [1]
Increases ATP production/efficiency of cellular respiration [1]

(d) Describe the role of structure F in protein synthesis. [4] [Structure F = Ribosome]

Site of protein synthesis/translation [1]
mRNA binds to ribosome [1]
tRNA brings amino acids to ribosome [1]
Peptide bonds formed between amino acids [1]
Ribosome moves along mRNA reading codons [1] [Accept 4 points for full marks]

Question 2 [15 marks]

(a) (i) With reference to Fig. 2.1, identify the phase where DNA replication occurs. [1]

Phase R/S phase [1]

(ii) State what happens during phase T. [2]

Mitosis occurs [1]
Cell division/cytokinesis [1]
Formation of two daughter cells [1] [Accept 2 points for full marks]

(b) A student added radioactive thymine to cells at the beginning of phase Q. Explain in which phase the radioactivity would first be observed in the nucleus. [3]

Radioactivity first observed in phase R/S phase [1]
Thymine is incorporated during DNA replication [1]
DNA replication occurs during S phase [1]

Point 1 to 2:

DNA content doubles [1]
Due to DNA replication during S phase [1]

Point 2 to 3:

DNA content remains constant [1]
No further DNA replication occurs during G2 phase [1]

Point 3 to 4:

DNA content halves [1]
Due to cell division/separation of sister chromatids [1]

(d) State three differences between mitosis and meiosis. [3]

Mitosis produces 2 cells, meiosis produces 4 cells [1]
Mitosis produces diploid cells, meiosis produces haploid cells [1]
Mitosis produces genetically identical cells, meiosis produces genetically different cells [1]
Mitosis involves one division, meiosis involves two divisions [1]
Crossing over occurs in meiosis but not mitosis [1] [Accept any 3 valid differences]

Question 3 [18 marks]

(a) Name the process responsible for the change in mass of the potato cylinders. [1]

Osmosis [1]

(b) Explain why the potato cylinders gained mass in distilled water (0.0 mol dm⁻³). [3]

Water potential of distilled water is higher than potato tissue [1]
Water moves from high to low water potential [1]
Water enters potato cells by osmosis [1]

0.4 mol dm⁻³ [1]

(ii) Explain how you determined this from the results. [2]

No change in mass at this concentration [1]
No net movement of water/equilibrium reached [1]

(d) Predict the percentage change in mass if the potato cylinders were placed in 1.2 mol dm⁻³ sucrose solution. Explain your prediction. [3]

Greater decrease than -15.3% / approximately -18% to -20% [1]
Higher concentration creates greater water potential gradient [1]
More water will move out of potato tissue [1]

(e) Describe how you would modify this experiment to investigate the effect of temperature on the rate of water movement. [4]

Use the same concentration of sucrose solution [1]
Place potato cylinders at different temperatures [1]
Measure mass change at regular time intervals [1]
Control other variables (pH, pressure, surface area) [1]

(f) State two variables that should be controlled in this investigation. [2]

Size/surface area of potato cylinders [1]
Volume of sucrose solution [1]
Temperature [1]
Time [1]
pH [1] [Accept any 2 valid variables]

(g) Suggest two sources of error in this experiment and how they could be reduced. [2]

Water on surface of cylinders - blot dry before weighing [1]
Evaporation - cover containers [1]
Measurement errors - use more precise balance [1]
Variation in potato tissue - use same potato/multiple replicates [1] [Accept any 2 valid error sources with solutions]

Question 4 [15 marks]

(a) Explain how enzymes increase the rate of biochemical reactions. [4]

Enzymes lower activation energy [1]
Provide alternative reaction pathway [1]
Form enzyme-substrate complex [1]
Active site complementary to substrate [1]
Substrate converted to product more easily [1] [Accept 4 points for full marks]

(b) (i) State the optimum pH for enzyme A and enzyme B. [2]

Enzyme A: pH 2 [1]
Enzyme B: pH 8 [1]

(ii) Suggest where in the human body enzyme A and enzyme B might be found. Give reasons for your answers. [4]

Enzyme A: Stomach [1]
Reason: Stomach has acidic pH (due to HCl) [1]
Enzyme B: Small intestine/pancreas [1]
Reason: Small intestine has alkaline pH (due to bile/pancreatic juice) [1]

pH affects ionization of amino acid side chains [1]
Changes in enzyme shape/conformation [1]
Active site no longer complementary to substrate [1]
Enzyme may denature at extreme pH [1] [Accept 3 points for full marks]

(d) State two other factors that affect enzyme activity. [2]

Temperature [1]
Substrate concentration [1]
Enzyme concentration [1]
Presence of inhibitors [1]
Presence of cofactors/coenzymes [1] [Accept any 2 valid factors]

Section B: Extended Response Question [20 marks]

Question 5 [20 marks]

(a) Describe the structure and properties of biological membranes and explain how they control the movement of substances into and out of cells. [12]

Mark Scheme:

Phospholipid bilayer structure [1]
Hydrophilic heads face outward, hydrophobic tails inward [1]
Fluid mosaic model with embedded proteins [1]
Cholesterol affects membrane fluidity [1]
Selective permeability [1]
Simple diffusion for small, non-polar molecules [1]
Osmosis for water movement [1]
Facilitated diffusion using channel/carrier proteins [1]
Active transport against concentration gradient using ATP [1]
Endocytosis and exocytosis for large molecules [1]
Role of membrane proteins as transporters [1]
Importance of concentration gradients [1]

[Award marks for clear explanations linking structure to function. Maximum 12 marks.]

(b) Discuss the importance of membrane transport processes in maintaining cellular homeostasis. [8]

Mark Scheme:

Definition of homeostasis [1]
Regulation of water balance through osmosis [1]
Control of ion concentrations (Na+, K+, Ca2+) [1]
Maintenance of pH through ion transport [1]
Glucose uptake for energy metabolism [1]
Removal of waste products [1]
Regulation of cell volume [1]
Maintenance of membrane potential [1]
Examples of consequences when transport fails [1]

[Award marks for clear discussion with examples. Maximum 8 marks.]

Quality of Written Communication:

Clear, logical structure
Appropriate use of biological terminology
Good use of examples
Coherent arguments linking transport to homeostasis