Topic 2- genes and health

Question 1

Describe and explain the effect alcohol concentration has on membrane permeability

Answer 1

Solvents such as ethanol increase membrane permeability. Lipids dissolve in alcohol, therefore, the phospholipids in a cell membrane will easily dissolve in solutions such as ethanol. As a result, the cell membrane becomes more fluid and permeable as it starts to break down.

Question 2

Describe and explain the effect temperature has on membrane permeability

Answer 2

The higher the temperature, the greater the kinetic energy and the faster the movement and diffusion of pigment molecules. Greater kinetic energy also causes phospholipids of the membrane to become more fluid and bonds between the fatty acid tails can begin to separate so that some pigment molecules can pass through.

Question 3

Explain the effects of CF on the digestive system

Answer 3

block pancreatic duct
enzymes not released to small intestine- less digestion
enzymes begin to digest pancease= hard cysts

Question 4

Explain the effects of CF on the reproductive system, incl. both males and females

Answer 4

-female thicker mucus plug on cervix- sperm cant enter
male- the vas deferens is blockedor non existent

Question 5

Explain the effects of CF on the respiratory system

Answer 5

thicker muscus (insert why) cant be moved along by cillia
makes diffusion distance longer
less oxygen enters blood
less respiration
less energy

Question 6

Explain how a faulty CFTR protein results in thicker, stickier mucus in CF sufferers

Answer 6

-ion channel is open as well as the CFTR channel being open/non existent
-water is constantly osmosis out of the mucus

Question 7

Explain the role of the CFTR protein

Answer 7

maintain the balance of Na+ and water in mucus

Question 8

Explain how and why the hydrolysis of amylopectin/glycogen stored in a cell would impact the movement of water via osmosis

Answer 8

less water in cell, so more would enter cell theough osmosis

Question 9

Under what conditions would water move into a cell via osmosis?

Answer 9

If a plant cell is surrounded by a solution that contains a higher concentration of water molecules than the solution inside the cell, water will enter the cell by osmosis

hypotonic solution

Question 10

Under what conditions would water move out of a cell via osmosis?

Answer 10

If a cell is in a hypertonic solution, the solution has a lower water concentration than the cell cytosol, and water moves out of the cell until both solutions are isotonic

hypertonic solution

Question 11

Give a definition of osmosis

Answer 11

a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.

Question 12

Explain how saturated and unsaturated phospholipid tails affects membrane fluidity

Answer 12

unsturated=less compact= more fluidity

Question 13

Explain how the level of cholesterol affects membrane fluidity

Answer 13

more cholesterol=less movement (holds tails togther)

Question 14

Explain why the cell membrane is called a fluid mosaic

Answer 14

multiple moving components

Question 15

List the other components of cell membranes and give a function for each

Answer 15

Transmembranic Channel protien- allows larger molecules to enter the cell through
cholesterol- provides strength by holding tails together and regulates fluidity

Question 16

Explain why phospholipids form a bilayer in cell membranes

Answer 16

head is hydrophilic and faces outwards
tail is hydrophobic and faces inwards

Question 17

Describe the structure of a fibrous protein

Answer 17

-long fibers of alpha helix secondary structure
-cross linked for strength
-insoluble

Question 18

Describe the structure of a globular protein

Answer 18

-spherical 3d shape
-insoluble
-can have specific shape for function (enzymes)

Question 19

Give the formula for Fick’s Law

Answer 19

rate of diffusion= surface area x concen dif
thickness of gas exchange sufface

Question 20

Explain the anatomical adaptations in organisms with respiratory systems that maximise gas exchange (make specific reference to surface area:volume ratio, thickness of exchange surface and concentration gradient)

Answer 20

avioli in lungs

surface area: volume ratio - more space for diffusion
thickness of surface- shorter diffusion distance
higher concerntration gradient- faster diffusion rate

Question 21

Explain the role of ciliated epithelial cells in the respiratory system

Answer 21

transports mucus- traps pathogens

Question 22

Explain the role of goblet cells in the respiratory system

Answer 22

has a higher surface area due to dip shape

secrete mucin and create a protective mucus layer

Question 23

Describe how the tertiary structure of a protein forms from the secondary structure

Answer 23

provides a 3d shape as the R goups with different charge form ionic bonds, further hydrogen bonds and disulphide bridges are further support as just hydrogen isnt strong enough (written as S-S)

Question 24

Describe how the secondary structure of a protein forms from the primary structure (make reference to alpha helix and beta pleated sheets)

Answer 24

primary structure is folded as either a alpha helix or beta pleated sheet by forming hydrogen bond between the carboxyl and NH groups

Question 25

Give a definition of the primary structure of a protein

Answer 25

the order of amino acids in a polypeptide chain

Question 26

Describe how amino acids react together to form a polypeptide

Answer 26

condensation reaction between amino acids forming a peptide bond between the NH and carboxyl groups of different amino acids

Question 27

Draw the structure of an amino acid, circle and label the functional groups

Answer 27

H R OH \ | // N-C-C / | \ H H H

Question 28

Describe the structure of a DNA mononucleotide

Answer 28

- Phosphate group - Deoxyribose sugar (pentose sugar) -Nitrogen containing base

Question 29

Describe how DNA mononucleotides join together to form a DNA polymer/strand

Answer 29

Condensation reaction between sugar and the phosphate group form a sugar phosphate backbone

Question 30

Describe the structure of a RNA mononcleotide

Answer 30

- phosphate group - Nitrogen containing base - ribose sugar (pentose sugar)

Question 31

Describe how DNA forms a double helix

Answer 31

through complimentary base paring of C and G and A and T with hydrogen bonds 2 antiparallel strands join at the base

Question 32

Describe the process of DNA replication

Answer 32

1) DNA helicase unwinds and unzips DNA, breaking the hydrogen bonds between base pairs, forming two separate strands that act as a template 2) The new DNA is built up from the 4 nucleotides in the nucleus 3) The nucleotides attach themselves to the bases on the old strands by complementary base pairing 4) DNA polymerase joins the new nucleotides to each other by strong phosphodiester bonds, forming the sugar phosphate backbone 5) the two new molecules are identical to the old one 1)Helicase 2) nucleotides 3) complementary 4) polymerase 5) identical

Question 33

Explain how Meselson and Stahl's experiment refuted the conservative model of DNA replication

Answer 33

An explanation which includes the following: • The conservative model was rejected / the semi-conservative model was accepted (1) • (due to) generation 1 has a single band which is halfway between 15N and 14N (1) • • (because) the DNA has one strand containing 15N and one strand containing 1N (1) (in semi-conservative model) further generations would have {a band which is halfway between 15N and 14N / no band at 15N } (1)

Question 34

Explain how Meselson and Stahl's experiment refuted the dispersive model of DNA replication

Answer 34

• The dispersive was rejected / the semi-conservative model was accepted (1) • (due to) generation 1 has a single band which is halfway between 15N and 14N (1) • (because) the DNA has one strand containing 15N and one strand containing 1N (1) (in semi-conservative model) further generations would have {a band which is halfway between 15N and 14N / no band at 15N } (1) dispersive was not pogging because there was a spilt between the heavy and light dna

Question 35

2) Explain how Meselson and Stahl's experiment provides evidence for the semi-conservative model of DNA replication

Answer 35

They cultivated bacteria colonies in one growth medium containing heavy nitrogen (N-15) and one growth medium containing light nitrogen (N-14). they then extracted dna from the bacteria from both growth mediums and put them into separate vials. they spun these vials in a centrifuge. The dna cultivated in the heavy nitrogen settled low down in its vial, whereas the dna cultivated in the light nitrogen settled high up in its vial. The scientists then transferred some of the bacteria that had been cultivated in the heavy nitrogen into a growth medium containing light nitrogen. they let the bacteria grow for 1 generation and then extracted the dna from it. They spun this dna in a centrifuge and it settled halfway between where the n-14 and n-15 dna settled. They let the bacteria grow in the n-14 growth medium for another generation, and spun it in the centrifuge. They repeated this for 5 generations. They found that after the second generation, the amount of dna that settled at the midpoint stayed the same, but an increasing number of dna molecules began to settle at the N-14 line again. This provided evidence for the semi conservative model as it shows that after the first generation, each dna molecule was made of a split of heavy and light nitrogen as the dna settled at the halfway point between heavy and light, which disproved the conservative theory. It also provided evidence for the semi conservative model as each increasing generation began to gather at the light nitrogen line, while the number of dna molecules at the midpoint stayed the same. This shows that each generation conserves the strand of heavy nitrogen dna along with producing new strands of dna using the light nitrogen from the growth medium.

Question 36

Describe the process of transcription

Answer 36

-DNA helicase unzips a section of dna by breaking the Hydrogen bonds and exposing the bases, into two strands were one is used as a template - complimentary base pairing occurrs but Uracil replaces T in the mRNA -RNA polymerase joins up the RNA making a mRNA molecule -RNA polymerase stops making mRNA when it reaches a stop signal on the DNA molecule - Once the mRNA has been made, the DNA strands coil back and hydrogen bonds reform -mRNA moves out of the nucleus, into the cytoplasm where it attaches to a ribosome

Question 37

Describe the process of translation

Answer 37

-Occurs in the ribosome in the cytoplasm -mRNA bonds to ribosome -tRNA with anticodon and a specific amino acid binds to codon via complimentary bade paring -adjacent amino acids join via condensation reactions forming peptide bonds -process stops when the primary structure of the protein is completed

Question 38

define codon and anticodon

Answer 38

codon is: Three bases on mRNA which code for one amino acid anticodon is: Three bases on tRNA, complementary to mRNA codon

Question 39

Describe the nature of the genetic code by defining the following: a) degenerate b) triplet code c) non-overlapping

Answer 39

Degenerate Most amino acids have more than one codon that relates to them Non-overlapping Each base is only read once Eg ABCDEF is ABC DEF not ABC CDE Universal All organisms use the same code, so the same codon always codes for the same amino acids

Question 40

1) Give the definition of a mutation

Answer 40

change in the arrangement of bases in DNA

Question 41

Describe the nature of the genetic code by defining the following: a) degenerate b) triplet code c) non-overlapping

Answer 41

a) degenerate- amino acids can have multiple codons that corespond to them b) triplet code- three bases code for an amino acid c) non-overlapping- each base is only counted once

Question 42

Give the definition of a mutation

Answer 42

a change in the arrangement of bases in a DNA molecule

Question 43

Explain the impact of a frameshift mutation on protein structure

Answer 43

a base is inserted or deleted from DNA, which shifts the whole code from that point, changing every triplet and therefore changing the amino acids that bind to them

Question 44

Explain why accurate DNA replication is important for protein synthesis

Answer 44

so the order of amino acids is correct, meaning the correct protien is made

Question 45

Explain the impact of a silent mutation on protein structure

Answer 45

nothing, a base is replace by another but dna is degenerate

Question 46

Explain the impact of a missense mutation on protein structure

Answer 46

changes only one amino acid therefor unlikely to impact overall protein structure

Question 47

Explain the impact of a nonsense mutation on protein structure

Answer 47

protien too short as the mution caused a stop codon in a base sequence

Question 48

define Genotype

Answer 48

combination of alleles an individual has

Question 49

define Phenotype

Answer 49

Characteristic caused by the genotype and evrioment

Question 50

define Homozygous

Answer 50

Two copies of the same allele

Question 51

define Heterozygous

Answer 51

Two different alleles in the genotype

Question 52

define Recessive gene

Answer 52

Only expressed in the phenotype if the individual is homozygous for the allele

Question 53

define Dominant allele

Answer 53

Expressed in the phenotype if one of these alleles is present in the genotype

Question 54

define Incomplete dominance

Answer 54

Each allele equally expressed in the phenotype

Question 55

define Gene

Answer 55

Sequence of DNA bases that codes for a sequence of amino acids in a polypeptide

Question 56

define Allele

Answer 56

Alternative form of a gene found at the same locus (position on chromosome)

Question 57

Give the genotype of an individual who is a symptomless carrier of a recessive disease

Answer 57

heterozygous

Question 58

State the differences between the two categories of cell: eukaryotic and prokaryotic cell

Answer 58

..

Question 59

Using a diagram, identify the following features of a prokaryotic cell: peptidoglycan cell wall, capsule, plasmid, flagellum, pili, ribosomes, mesosomes and circular DNA give a function for each

Answer 59

…

Question 60

name the organelles in Eurakyotic cells

Answer 60

-nucleus -cell surface membrane -mitochondria -Centrioles -rough/smooth endoplasmic reticulum -Lysosomes -Golgi