A-Level Biology Key Concepts

Question 1

Which organelle is the site of aerobic respiration in eukaryotic cells?

Accepted Answer

Mitochondrion

Answer

Chloroplast

Answer

Ribosome

Answer

Golgi apparatus

Question 2

During the light-dependent reactions of photosynthesis, what is the role of photolysis?

Accepted Answer

Splitting water molecules to release electrons, protons, and oxygen

Answer

Breaking down glucose into pyruvate

Answer

Fixing carbon dioxide into organic molecules

Answer

Reducing NADP to form NADPH without water

Question 3

In DNA replication, what is the function of DNA helicase?

Accepted Answer

Unwinding the double helix by breaking hydrogen bonds between base pairs

Answer

Joining Okazaki fragments on the lagging strand

Answer

Adding complementary nucleotides to the template strand

Answer

Proofreading newly synthesised DNA for errors

Question 4

What type of transport moves glucose into epithelial cells of the small intestine against its concentration gradient?

Accepted Answer

Co-transport (secondary active transport) with sodium ions

Answer

Simple diffusion

Answer

Facilitated diffusion through channel proteins

Answer

Endocytosis

Question 5

Which statement correctly describes the role of tRNA in translation?

Accepted Answer

It carries specific amino acids to the ribosome and has an anticodon that pairs with mRNA codons

Answer

It carries the genetic code from the nucleus to the cytoplasm

Answer

It forms the structural component of ribosomes

Answer

It catalyses the formation of peptide bonds between amino acids

Question 6

In a food chain, approximately what percentage of energy is typically transferred from one trophic level to the next?

Accepted Answer

10%

Answer

50%

Answer

90%

Answer

1%