Topic 2

Question 1

Amino Acids - structure

Answer 1

• H(2)NCHRCOOH
• amine (H2N) + carboxylic acid (COOH)
• peptide bond
• condensation reaction

Question 2

Protein Structure- primary

Answer 2

• SEQUENCE and NUMBER of AMINO ACIDS in polymer

- determined by genes

Question 3

Protein Structure - secondary

Answer 3

• INTERACTIONS between amino acids
  
  1. alpha helix - globular proteins, soluble
  2. beta pleated sheet - fibrous proteins, insoluble

Question 4

Protein Structure - tertiary

Answer 4

• determines WHAT structure DOES

Question 5

Protein Structure - quaternary

Answer 5

• only for proteins with MORE THAN ONE POLYPEPTIDE

- eg haemoglobin, collagen

Question 6

Mucus Regulation - too runny

Answer 6

1. NA IONS OUT of MUCUS through Na pump (ENaC) into tissue fluid
2. POTENTIAL DIFFERENCE created - due to raised Na conc in tf
3. ELECTRICAL GRADIENT formed causing Cl to MOVE put of MUCUS into tissue fluid - diffuse between gap in cells
4. WATER drawn OUT of cell by osmosis into tissue fluid

Question 7

Mucus Regulation - too sticky

Answer 7

1. Cl IONS OUT of TISSUE FLUID through CFTR channel into mucus
2. ELECTRICAL GRADIENT between mucus and tf
3. Na ions diffuse out of tf into mucus
4. WATER drawn out of cell INTO MUCUS - osmosis

Question 8

Mucus Regulation - cystic fibrosis

Answer 8

• CFTR missing or non functional
  1. Cl ions can’t pass into mucus
  2. Na pump not blocked so Na drawn into tissue fluid
  3. Cl follows it into tf (electrical gradient)
  4. mucus becomes even thicker

Question 9

Nucleotides - structure

Answer 9

Phosphate, Deoxyribose (sugar), Organic base (A,T,C,G)

- joined by condensation reaction

Question 10

Polynucleotides

Answer 10

• Strand joined by phosphodiester bond
• two strands form DOUBLE HELIX - joined by hydrogen b
• antiparallel structure

Question 11

Transcription - process

Answer 11

Copying a gene’s DNA sequence to make an RNA molecule

1. RNA polymerase attaches to DNA
2. Hydrogen bonds between bases break
3. Template strand transcribed - mRNA molecule w/ same base sequence as DNA coding strand
4. Complementary RNA nucleotides align into position
5. Phosphodiester bonds form
6. mRNA molecule produced

Question 12

Translation - process

Answer 12

Turning sequence of bases into sequence of amino acids

1. mRNA attaches to ribosome
2. tRNA molecules comp base pair w/ mRNA
3. Next tRNA molecule binds to mRNA and peptide bond forms between the two amino acids
4. the ribosome moves along mRNA
5. first tRNA molecule leaves - leaving the amino acid

Question 13

Nature of Genetic Code - triplet code

Answer 13

• Non overlapping

- Degenerate - several code for same aa

Question 14

DNA replication - process

Answer 14

1. DNA unwinds - H bonds break
2. free DNA nucleotides line up alongside DNA strand - H bonds form
3. DNA polymerase links adjacent nucleotides w/ phosphodiester bonds - forming new comp strand (original strand as template)
4. Two new DNA molecules formed - semiconservative replication

Question 15

Genetic Screening

Answer 15

Amniocentesis
- insert needle into amniotic fluid to collect foetal cells
- 15-17 weeks
- 1% chance miscarriage
Chronic Villus Sampling
- Placental tissue removed through wall of abdomen or vagina
- 8-12 weeks
- 1-2% chance miscarriage

Question 16

Non Invasive methods of screening

Answer 16

Non-Invasive Prenatal Diagnosis
- analyse DNA fragments in mothers blood plasma - some DNA from embryo
- 7-9 weeks
- no miscarriage risk
Preimplantation Genetic Diagnosis
- IVF
- cell removed and tested - then implanted
- low success and live birth rate rate (30%)