AQA A-LEVEL BIOLOGY COMPLETE QUESTIONS AND
ANSWERS WITH VERIFIED SOLUTION GRADE A+
1. The theory of endosymbiosis suggests that:
A. Chloroplasts and mitochondria were once free-living bacteria.
B. Viruses are a major cause of cancer.
C. Plants evolved from animal-like ancestors.
D. All eukaryotic cells were originally prokaryotic.
Answer: A) Chloroplasts and mitochondria were once free-living
bacteria.
Rationale: The theory of endosymbiosis posits that mitochondria and
chloroplasts originated from free-living prokaryotes that were engulfed
by early eukaryotic cells.
2. The process by which a DNA molecule is copied to form two
identical molecules is called:
A. Replication
B. Transcription
C. Translation
D. Duplication
Answer: A) Replication
Rationale: DNA replication is the process by which a DNA molecule is
copied to produce two identical molecules, ensuring genetic material is
passed on during cell division.
,3. What is the main purpose of the process of fermentation?
A. To produce oxygen
B. To regenerate NAD+
C. To produce ATP
D. To produce glucose
Answer: B) To regenerate NAD+
Rationale: Fermentation allows glycolysis to continue by regenerating
NAD+ when oxygen is not available.
4. In the human circulatory system, where does oxygenated blood first
enter after being pumped from the lungs?
A. Left atrium
B. Left ventricle
C. Right atrium
D. Right ventricle
Answer: A) Left atrium
Rationale: Oxygenated blood from the lungs enters the left atrium
before being pumped into the left ventricle for distribution to the body.
5. Which of the following describes a homogenous mixture?
A. Blood
B. Sand and water
C. Oil and water
, D. Salad dressing
Answer: A) Blood
Rationale: Blood is a homogenous mixture because its components
(plasma, red blood cells, white blood cells, and platelets) are evenly
distributed.
6. In which stage of the cell cycle does DNA replication occur?
A. G1
B. S phase
C. G2
D. M phase
Answer: B) S phase
Rationale: DNA replication occurs during the S phase of interphase,
ensuring each daughter cell receives a full set of chromosomes.
7. Which of the following is true about the DNA structure?
A. It is made up of a single strand of nucleotides.
B. The two strands are held together by hydrogen bonds between
complementary base pairs.
C. The sugar-phosphate backbone is found in the interior of the helix.
D. Each strand contains only one type of nucleotide.
Answer: B) The two strands are held together by hydrogen bonds
between complementary base pairs.
ANSWERS WITH VERIFIED SOLUTION GRADE A+
1. The theory of endosymbiosis suggests that:
A. Chloroplasts and mitochondria were once free-living bacteria.
B. Viruses are a major cause of cancer.
C. Plants evolved from animal-like ancestors.
D. All eukaryotic cells were originally prokaryotic.
Answer: A) Chloroplasts and mitochondria were once free-living
bacteria.
Rationale: The theory of endosymbiosis posits that mitochondria and
chloroplasts originated from free-living prokaryotes that were engulfed
by early eukaryotic cells.
2. The process by which a DNA molecule is copied to form two
identical molecules is called:
A. Replication
B. Transcription
C. Translation
D. Duplication
Answer: A) Replication
Rationale: DNA replication is the process by which a DNA molecule is
copied to produce two identical molecules, ensuring genetic material is
passed on during cell division.
,3. What is the main purpose of the process of fermentation?
A. To produce oxygen
B. To regenerate NAD+
C. To produce ATP
D. To produce glucose
Answer: B) To regenerate NAD+
Rationale: Fermentation allows glycolysis to continue by regenerating
NAD+ when oxygen is not available.
4. In the human circulatory system, where does oxygenated blood first
enter after being pumped from the lungs?
A. Left atrium
B. Left ventricle
C. Right atrium
D. Right ventricle
Answer: A) Left atrium
Rationale: Oxygenated blood from the lungs enters the left atrium
before being pumped into the left ventricle for distribution to the body.
5. Which of the following describes a homogenous mixture?
A. Blood
B. Sand and water
C. Oil and water
, D. Salad dressing
Answer: A) Blood
Rationale: Blood is a homogenous mixture because its components
(plasma, red blood cells, white blood cells, and platelets) are evenly
distributed.
6. In which stage of the cell cycle does DNA replication occur?
A. G1
B. S phase
C. G2
D. M phase
Answer: B) S phase
Rationale: DNA replication occurs during the S phase of interphase,
ensuring each daughter cell receives a full set of chromosomes.
7. Which of the following is true about the DNA structure?
A. It is made up of a single strand of nucleotides.
B. The two strands are held together by hydrogen bonds between
complementary base pairs.
C. The sugar-phosphate backbone is found in the interior of the helix.
D. Each strand contains only one type of nucleotide.
Answer: B) The two strands are held together by hydrogen bonds
between complementary base pairs.
