Cystic Fibrosis

Question 1

define diffusion

Answer 1

diffusion is the net movement of particles from an area of high concentration to an area of low concentration

Question 2

what is Fick’s Law?

Answer 2

rate of diffusion = area of diffusion surface x difference in concentration/thickness of diffusion surface

Question 3

explain how the term ‘partially permeable’ applies to the cell membrane

Answer 3

small molecules can move through gaps in the phospholipids, but large or charged molecules must pass through gated/channel proteins

Question 4

define osmosis

Answer 4

the diffusion of free water molecules across a partially permeable membrane from an area of high concentration to an area of low concentration

Question 5

what is active transport?

Answer 5

uses energy to move molecules and ions across plasma membranes against a concentration gradient

Question 6

How does active transport work?

Answer 6

• molecule attaches to carrier protein, protein changes shape, releases molecule
• energy comes from hydrolysis of ATP

Question 7

what is endocytosis?

Answer 7

• cell surrounds molecule with a section of its cell membrane
• membrane pinches off to form vesicle
• uses ATP

Question 8

what is exocytosis?

Answer 8

• vesicles containing substances are pinched off from the sacs of the golgi
• vesicles fuse with the cell membrane and release their contents outside the cell
• uses ATP

Question 9

describe what is meant by ‘secondary structure’

Answer 9

hydrogen bonds form between amino acids in polypeptide, its coils into an alpha helix or beta pleated sheet

Question 10

describe what is meant by ‘tertiary structure’

Answer 10

further coiling; more hydrogen bonds, ionic bonds and disulfide bridges are made

Question 11

describe what is meant by ‘quaternary structure’

Answer 11

some proteins are made from several different polypeptides held together by bonds

Question 12

describe the 3D structure of a globular protein

Answer 12

• round, compact proteins
• made from multiple polypeptide chains
• chains coiled so that hydrophilic parts of the chain are on the outside of the molecule, and hydrophobic parts are on the inside

Question 13

describe the 3D structure of a fibrous protein

Answer 13

• fibrous proteins are made from long, insoluble polypeptides
• chains are held together by lots of bonds

Question 14

what does the induced theory state?

Answer 14

the substrate doesn’t just have to be the right shape to fit the active site, but it also has to make the active site change in the right way

Question 15

describe how carrier proteins facilitate the movement of molecules

Answer 15

• large molecule attaches to carrier protein in the membrane
• protein changes shape
• releases molecule on the other side of the membrane

Question 16

describe how channel proteins facilitate diffusion

Answer 16

-channel proteins form pores in the membrane that allow charged particles to diffuse through

Question 17

why are globular proteins soluble?

Answer 17

they are arranged to have hydrophilic groups on the outside of the molecule

Question 18

what is a gene?

Answer 18

a sequence of mononucleotide bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide

Question 19

describe the structure of tRNA

Answer 19

has an amino acid binding site at one end, and a sequence of three bases on the other, called an anticodon

Question 20

describe the structure of collagen

Answer 20

• made up of amino acids in a repeating sequence of 3 (usually glycine, proline and hydroxyproline)
• primary structure is twisted into a helix held by hydrogen bonds
• three helices twisted together into a triple superhelix

Question 21

describe the structure of haemoglobin

Answer 21

• globular protein
• has iron containing haem groups that allow it to bind to oxygen
• 4 haem groups allow it to carry a large amount of Oxygen
• co-operative binding

Question 22

what does co-operative binding mean (in reference to haemoglobin)?

Answer 22

• changes shape when it binds to an oxygen group to that it binds to the next one more easily
• means it is good at binding when there is a high amount of oxygen

Question 23

give ways in which the structure of the lung is adapted for rapid gaseous exchange

Answer 23

• lots of alveoli for large surface area
• small thickness of alveolar epithelium and capillary endothelium
• good blood supply from capillaries = high concentration gradient

Question 24

why does the membrane have high permeability at low temperatures?

Answer 24

• membrane is rigid due to low temperature
• however, channel proteins deform, increasing permeability
• ice crystals may pierce the membrane

Question 25

why does the membrane have high permeability at temperatures exceeding 45 degrees?

Answer 25

- bilayer melts - water expands, putting pressure on the membrane - channel proteins and carrier proteins deform

Question 26

what are stop and start codons?

Answer 26

used to tell the cell when to stop and start production of a protein, found at the beginning and end of a gene

Question 27

what does the term 'degenerate' refer to in reference to the genetic code?

Answer 27

there are more possible combinations of triplets than there are amino acids. means that more than one triplet can be used to code for one amino acid

Question 28

outline the process of DNA replication

Answer 28

- DNA helicase breaks hydrogen bonds between polynucleotide strands - free floating DNA nucleotides are attracted to complementary exposed bases on each strand - condensation reactions join nucleotides, catalysed by DNA polymerase

Question 29

what does the term 'incomplete dominance' mean?

Answer 29

when the trait from a dominant allele isnt completely shown over the trait produced by the recessive allele, so both alleles influence the phenotype

Question 30

what does the term 'monohybrid inheritance' mean?

Answer 30

inheritance of a single characteristic controlled by different alleles.