Biology Important Questions

Question 1

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. (5 marks)

Answer 1

Micelle contains bile salts and fatty acids
Makes fatty acids soluble
Fatty acids absorbed by diffusion
Triglycerides form
Vesicles move to cell membrane

Question 2

Describe how mRNA is formed by transcription in eukaryotes (5 marks)

Answer 2

Hydrogen bonds break by DNA helicase
One strand of DNA acts as a template
Free RNA nucleotides align by complementary base pairings
RNA polymerase joins nucleotides by phosphodiester bonds
Uracil instead of Thymine
Pre-mRNA is spliced

Question 3

Describe how a polypeptide is formed by translation of mRNA (6 marks)

Answer 3

mRNA leaves via a nuclear pore to the ribosome
tRNA anticodon is complementary to the mRNA codon
tRNA brings specific amino acids
Joined by peptide bonds using ATP
Ribosome moves along the mRNA strand to form a polypeptide
tRNA released to collect another amino acid

Question 4

Describe and explain 5 ways which substances are transported across cell membranes (5 marks)

Answer 4

Diffusion - small molecules down a concentration gradient
Facilitated diffusion - down a concentration gradient via protein carrier
Osmosis - water down a potential gradient
Active transport - against a concentration gradient using ATP and carrier protein
Co-transport - 2 substances using a carrier protein

Question 5

Describe the structure of DNA (5 marks)

Answer 5

Polymer of nucleotides
Adenine, thymine, cytosine and guanine
Deoxyribose, phosphate and nitrogenous base
Double helix
Phosphodiester bonds