genes and health Flashcards
(59 cards)
1
Q
why can large polar molecules not move through cell membranes
A
- too large
- no channel/ carrier proteins
- repelled by hydrophobic fatty acid tails
2
Q
compare and contrast diffusion and active transport
A
- both move molecules through cell surface membrane
*in both molecules can move through proteins
*diffusion is down a concentration gradient but active transport is against - diffusion does not require ATP but active transport does
3
Q
compare and contrast endocytosis and exocytosis
A
- both involve vesicles
- both involve energy from ATP
- exo involves substances leaving cell but endo involves substances entering cell
- exo involves vesicles fusing w cell surface membrane but endo involves forming vesicles from cell surface membrane
4
Q
what are the functions of glycoproteins found in the cell surface membrane?
A
- cell recognition
- antigens
- receptors on cell surface membrane
5
Q
how does the structure of a phospholipid molecule contribute to the partial permeability of a cell surface membrane?
A
- contains a polar head and non polar fatty acid chains
- allows non polar molecules to pass through
*polar molecules cannot move through
6
Q
what is meant by the term gene?
A
- sequence of bases in DNA
*that codes for a sequence of amino acids
7
Q
what is the role of tRNA in the production of proteins?
A
- tRNA molecules transport amino acids to the ribosome
- tRNA molecule has an anticodon that binds to a complementary codon on the mRNA
*each tRNA carries a particular amino acid - tRNA bonds to ribosome
8
Q
how does the primary structure of a protein allow it to be soluble in water
A
*sequence of amino acids determines the folding of the polypeptide
* forming a globular structure
*hydrophobic R groups located in the centre of the protein
* hydrophilic R groups located on the outside of the protein
* water forms h bonds with hydrophilic groups
9
Q
what effect does removing one base from a DNA sequence have on the protein structure? (deletion)
A
- could effect every codon
- like to affect the position of the stop/ start codon
- results in diff sequence of amino acids
10
Q
what effect does changing one base for another in a DNA sequence have on the protein structure? (substitution)
A
- only effects one codon
- may not affect the sequence of amino acids
- may code for the same amino acid due to the degenerate nature of the genetic code
11
Q
what is the importance of primary structure for functioning of enzymes?
A
- determines interaction between amino acids
- primary structure determines folding and tertiary structure
- affecting the shape of the active site
12
Q
what is the effect on an increase of temperature on enzyme activity?
A
- more kinetic energy available
- so more frequent collisions between between enzyme and substrate
- more enzyme- substrate complexes formed
- but when too high, enzyme denatures
- so substrate no longer fits active site
13
Q
why are enzymes described as biological catalysts?
A
they are proteins which reduce activation energy of biological reactions
14
Q
how can a single base mutation lead to an altered primary structure?
A
- changing a base results in a change in the triplet code
- this changes the codon in the mRNA
- resulting in a different amino acid sequence
15
Q
what happens to proteins that become extracellular enzymes after translation until they are released from the cell?
A
- folded in the RER
- transported in vesicles
- modified in the Golgi apparatus
- exocytosis
16
Q
compare and contrast transcription with DNA replication
A
- both involve formation of phosphodiester bonds
- both involve DNA helicase unzipping the DNA
- transcription uses RNA nucleotides but replication uses DNA nucleotides
- transcription uses RNA polymerase but replication uses DNA polymerase
- transcription produces a single strand of mRNA but replication produces double stranded DNA
- replication produces identical copies but transcription produces a complementary copy
17
Q
how does a change of one amino acid lead to a change in the structure and properties of haemoglobin?
A
- different primary structure
- different R group
- tertiary structure will change
- due to change in disulphide bridges
- haemoglobin may not bind to oxygen
18
Q
how could a frameshift mutation result in the production of a protein with a shorter primary structure?
A
- changes the triplet code
- introducing a new stop codon
- coding for a shorter sequence of amino acids
19
Q
how is mRNA synthesised at a template strand of DNA?
A
- RNA nucleotides align with complementary bases on DNA
- RNA nucleotides joined together by phosphodiester bonds
20
Q
what is the difference between the structure of DNA and RNA?
A
- DNA is double stranded but RNA is single stranded
- DNA contains deoxyribose but RNA contains ribose
- DNA contains T but RNA contains U
21
Q
how do nucleotides join together to form DNA?
A
- condensation reaction
- phosphodiester bonds
- DNA polymerase
22
Q
why are men with cystic fibrosis less likely to be able to release sperm?
A
- sperm duct blocked with mucus so sperm cannot leave testes
23
Q
why do people with cystic fibrosis require a higher energy diet?
A
- enzymes cannot enter intestine because pancreatic duct blocked with mucus
- digestion is less efficient
24
Q
why are people with cystic fibrosis more likely to develop problems in the pancreas?
A
- pancreatic enzymes trapped behind mucus damage pancreatic cells such as those that produce insulin
- cysts form in pancreas
25
why does cystic fibrosis affect the rate of oxygen uptake in the lungs?
* thick sticky mucus
* cannot be moved by cilia
* restricting air flow through bronchi
* increasing diffusion distance/ reducing surface area for gas exchange in the alveoli
26
why is thicker mucus produces if the functioning of the CFTR channel protein is impaired?
* Cl- cannot enter mucus/ leave cell
* Na+ do not move into the mucus/ out of the cells
* so water moves out of mucus by osmosis
27
what is the role of mRNA in protein synthesis?
* carries genetic code for a protein
* binds to ribosome
* complementary tRNA anticodon binds to mRNA codon
* sequence of bases on mRNA determines sequence of amino acids
28
how do Cl- move through the basal membrane? (into cell)
* active transport
* against conc grad
* energy from ATP
29
how do Cl- move through the apical membrane? (out of cell)
* facilitated diffusion
* down conc grad
30
explain direction of movement of water molecules caused by Cl- moving into mucus
* higher concentration of Cl- in the mucus than the tissue fluid
* water would move into the mucus by osmosis
* from a higher concentration of free water molecules to a lower concentration in the mucus
31
chorionic villus sampling
* cells taken from placenta
* 10-14 weeks
* earlier diagnosis
32
amniocentesis
* amniotic fluid containing cells
* 14-20 weeks
* lower risk of miscarriage
33
Why did meselson and stahl accept one model for DNA replication and reject the other?
Semi conservative model was accepted
Gen 1 has a single band halfway between 15N and 14N
Because DNA has one strand with 15N and one with 14N
In semi conservative, further generations would have no band at 15N
34
Describe how DNA is organised in a bacterial cell
Large circular DNA
Not associated with histone proteins
Small plasmids
Located in the cytoplasm
35
Explain the role of the enzyme ligase in DNA replication
Joins sections of DNA together
By forming phosphodiester bonds
Between phosphate and sugar
36
describe the roles of transcription and translation in the synthesis of a globular protein by a muscle cell
gene for the protein is transcribed
complementary base pairing between RNA nucleotides and DNA
mRNA leaves nucleus and attaches to a ribosome
pairing between codons on mRNA and anticodons on tRNA
tRNA provides specific amino acids
sequence of bases determines the primary structure of the protein
37
compare and contrast the structure of a DNA double helix with the structure of tRNA
both contain nucleotides/ phosphate group, pentose sugar and base
both contain phosphodiester bonds/ h bonds between bases
DNA is double stranded but tRNA is single stranded
DNA contains deoxyribose sugar/ thymine but tRNA contains ribose/ uracil
tRNA has a specific amino acid binding site
38
describe the role of the CFTR protein in ensuring that the mucus produced in the lungs has the right consistency
Cl- leave cells thru CFTR protein
Na+ leave cells
increasing solute conc in mucus
water moves out of the cells and into the mucus by osmosis
39
which statistical test is used to determine if a difference is significant?
students t test
40
give reasons for the variation in the lung volumes of healthy individuals
diff height/ weight/ mass
diff gender/ sex
diff age
41
give 2 diffs between endocytosis and exocytosis
exo involves molecules/ substances leaving the cell but endo involves molecules/substances entering the cell
exo involves vesicles fusing w cell surface membrane but endo involves the formation of vesicles
42
explain how phospholipids form a cell surface membrane
hydrophilic parts/phosphate groups associate w water
hydrophobic parts/ fatty acids associate with each other/ repel water
a bilayer forms w hydrophobic parts pointing towards each other
43
explain why individuals w a smaller sa: vol will tire more easily than healthy individuals
increased diffusion distance for gas exchange
reduction in oxygen uptake
less oxygen for aerobic respiration
leading to more anaerobic respiration causing fatigue
44
explain why the phospholipids are arranged in 2 layers in a cell surface membrane
hydrophilic region/ phosphate head/ polar region orientated towards water
hydrophobic region/ fatty acids tail away from water
need 2 layers as aqueous solution either side of cell membrane
45
describe the function of carrier proteins in a cell surface membrane
involved in facilitated diffusion
from a high to low conc
movement of large/ polar molecules
involved in active transport
needs ATP to move molecules against conc grad
46
describe how glucose enters muscle cells thru the cell membrane
carrie proteins
facilitated diffusion
47
explain why different mutations in the CFTR gene can lead to differences in the severity off the symptoms of cystic fibrosis
diff effect on the protein produced
chloride ion transport affected by the extent of changes to the protein
varying the thickness/ stickiness of the mucus
48
why do children w cystic fibrosis need to be given dietary supplements and digestive enzymes
thicker stickier mucus
blocks pancreatic duct
prevents enzymes digesting carbs/ proteins/ lipids
reduced absorption of products of digestion into the blood
less amino acids/ vitamins/ minerals slows growth rate
digestive enzymes/ dietary supplements would increase growth rate
49
what does the CFTR gene code for
a channel protein
50
why may a couple choose not to have choronic villus sampling
test result may be inaccurate
increased risk of miscarriage
false pos may lead to termination of healthy foetus
51
explain what is meant by an inherited recessive disorder
caused by a faulty allele
only expressed in the homozygous condition
52
state what is meant by the term allele
alternative form of a gene
found at the same locus
53
what does interferon do
inhibit viral replication inside cells
54
compare and contrast the molecular structures of globular and fibrous proteins
both are chains of amino acids joined by peptide bonds
both contain h bonds/ ionic/ disulphide bridges
globular proteins have hydrophilic groups on the outside where as fibrous have hydrophobic
globular have tertiary or quaternary structure whereas fibrous have little or no tertiary structure
globular are folded into compact shapes whereas fibrous have long chains
55
describe how a peptide bond is formed
condensation reaction
between amine group/ NH2 and the carboxyl group/COOH of adjacent amino acids
56
name elements not found in carbohydrates which may be in R groups
nitrogen
sulfur
57
name the products formed when several amino acids are joined together
polypeptide
water
58
describe the structure of collagen
primary structure described as a repeating amino acid sequence
three polypeptide chains
chains coiled around each other
cross-linking between the chains
59
describe the primary structure of a protein
sequence of amino acids
joined together by peptide bonds
