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Flashcards in ILA Deck (21)
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1

what is the process of DNA transcription?

1. topoisomerase unwinds the DNA supercoils
2. DNA helicase breaks H+ bonds and exposes the nucleotides
3. SSBs coat the DNA strands to prevent annealing
4. RNA polymerase binds at TATA promotor region
5. moves in 3' to 5' direction
6. adds one ribonucleotide at a time until stop codon is reached
7. mRNA strand is produced with poly-A tail and 5' cap

2

what is the process of splicing?

it is the removal of introns to form a fully coding strand
carried out in nucleus by splicosomes
exons are spliced back together
mature mRNA leaves nucleus via nuclear pores

3

what happens during translation?

1. mRNA binds to a ribosome which has small and large
subunits with an APE section in the large subunit
2. tRNA carries anticodons
3. tRNA binds to the ribosome
4. mRNA moves in a 3’ to 5’ direction and the anticodon
binds to mRNA
5. As each amino acid is bound the mRNA shifts along the
ribosome
6. At termination codon the ribosome detaches and mRNA is
broken down in the cytosol

4

what are single nucleotide polymorphisms (SNPs)?

• DNA sequence variation when a single nucleotide (ATCG)
differs between people
• Can result in a different codon which generates a different
protein and thus disease
• E.g. sickle cell anaemia or cystic fibrosis
• Can affect recognition/promoter/termination sequences to change the length of proteins

5

what are the subunits of haemoglobin?

2 x alpha
2 x beta

6

what is sickle cell anaemia caused by?

normal haemoglobin - HbA
sickle cell haemoglobin = HbS
affects primary structure
GAG to GTG on 17th nucleotide
(single nucleotide polymorphism)
autosomal recessive

7

what is the inheritance of sickle cell anaemia?

autosomal recessive
if both parents have it = 1/4

8

what functional changes occur i n sickle cell anaemia?

• Cells don’t live as long
• Lower affinity for oxygen
• Gets stuck in blood vessels
• Overall, leads to reduced delivery of O2 to muscles

9

what is the primary structure of proteins? What bonds are present?

chain of amino acids
covalent bonds

10

what is the secondary structure of proteins? what bonds are present?

alpha helix, beta pleated sheets
H+ bonds

11

what is the tertiary structure of proteins?

3D structure

12

what bonds occur in the tertiary structure of proteins?

van der waals
H+ bonds
electrostatic
ionic
disulphide bridges

13

what is the quaternary structure of proteins?

the overall 3D structure of protein

14

what is osmolality?

concentration of solution expressed as solute particles per kg

15

what is osmolarity?

concentration of solution expressed as solute particles per L

16

what is oncotic pressure?

pressure exerted by plasma proteins on capillary wall

17

what is osmosis?

the process by which molecules within a solvent pass through a semi permeable membrane from a high concentration to a low concentration

18

what is the role of the hypothalamus and osmoreceptors in water homeostasis?

• Osmoreceptors within hypothalamus detect when water potential in the blood is low
• Loss of water reduces their volume which triggers stimulation of nerve cells in the hypothalamus
• This triggers ADH to be released from the posterior pituitary

19

what is the role of the posterior pituitary and vasopressin in water homeostasis?

• Posterior pituitary is stimulated by the hypothalamus
• Action potentials travel down and cause ADH to be released into
the blood stream
• This then acts on the kidneys, resulting in increased fluid
retention

20

what happens in the kidney during water conservation?

In water conservation
• Urine is diluted as it moves through the loop of Henle
• It is concentrated again in the distal tubules and collecting ducts
• The descending loop is impermeable to sodium chloride and permeable to water
• The ascending loop is permeable to sodium chloride and impermeable to water
• Once dilute urine enters the distal tubules, water is reabsorbed without sodium chloride -> concentrated urine

21

what is the role of the kidney in sodium homeostasis?

• When renal blood flow is reduced, juxtaglomerular cells convert prorenin to renin
• Plasms renin then converts angiotensinogen to angiotensin I
• This is converted to angiotensin II by ACE
• Angiotensin II increases blood pressure via vasoconstriction and simulates secretion of aldosterone from the adrenal cortex
• Aldosterone causes renal tubules to increase the reabsorption of
sodium and water into the blood (and excretion of potassium)
• This increases the volume of ECF and increases blood pressure