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A Level Biology : Content > Topic 2A&B: Gas Exchange, Cell Membranes, Transport and Proteins > Flashcards

Topic 2A&B: Gas Exchange, Cell Membranes, Transport and Proteins Flashcards

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1
Q

What does Fick’s Law states

A

The larger the surface area, difference in concentration and shorter the diffusion distance the quicker the rate of diffusion

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2
Q

Define diffusion

A

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration

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3
Q

How does surface area to volume ratio affect transport of molecules?

A

The lower the surface area to volume ratio, the further distance molecules need to travel to reach all parts of the organism

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4
Q

How are gas exchange surfaces adapted for efficient diffusion?

A

Gas exchange surfaces have large surface area to volume ratio (smaller objects) and are thin which provides shorter diffusion pathway across the gas exchange

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5
Q

How is the mammalian lung adapted for gas exchange?

A

The mammalian lungs have lots of alveoli which provides them with large surface area for diffusion to occur across

The alveolar epithelium and capillary endothelium are each only one cell thick giving short diffusion pathway

Alveoli have a good blood supply meaning that oxygen is taken away and more carbon dioxide is brought constantly which maintains concentration gradient

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6
Q

What is meant by the Fluid Mosaic Model

A

Cell membranes are fluid and have a mosaic-like arrangement of proteins

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7
Q

What evidence led to the development of the fluid-mosaic model?

A

Electron microscope images appeared to show three layers in a cell membrane hence why scientists believed that cell membranes are composed of a phospholipid layer between two continuous layers of proteins

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8
Q

What is the main function of cell membranes

A

Controlling the movement of substances in and out of the cell or organelle

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9
Q

What are cell membranes composed of

A

phospholipid bilayer

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10
Q

what makes up the phospholipid bilayer

A

hydrophilic phosphate heads faving out towards water on either side of membrane

two hydrophobic fatty acid tails facing inside making the centre hydrophobic

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11
Q

glycoproteins

A

proteins with polysaccharide chain

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12
Q

glycolipids

A

lipids with polysaccharide chain

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13
Q

osmosis

A

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

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14
Q

facilitated diffusion

A

the net movement of large particles from an area of high concentration to an area of low concentration down their concentration gradient using carrier or channel proteins

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15
Q

explain how a carrier protein moves a large molecule into or out of the cell

A

large molecule attached to a carrier protein in the membrane

protein changes chape

molecule is released on the opposite site of the membrane

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16
Q

explain how channel proteins move charged particles into or out of the cell

A

they have pores through which the charged particles can diffuse through

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17
Q

which proteins is involved in active transport

A

carrier

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18
Q

active transport

A

the movement of molecules and ions from an area of low concentration to an area of high concentration against a concentration gradient using ATP

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19
Q

explain how carrier proteins work during active transport

A

molecule attaches to the carrier protein

protein changes chape

molecule released on the other side of the membrane

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20
Q

process of endocytosis

A

a cell surrounds a substance with a section of its membrane and the membrane then pinches off to form a vesicle inside the cell containing the ingested substance

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21
Q

does endo and exo cytsosis use ATP

A

yes

22
Q

process of exocytosis

A

vesicles containing the substance pinch off from the golgi apparatus and move towards cell membrane where they fuse with it and content is released outside the cell

23
Q

what makes up an amino acid

A

carboxyl group

amino group

variable group containing a carbon

24
Q

how are polypeptides formed

A

amino acids joined together via condensation reaction

water released

peptide bonds formed

25
Q

primary structure of protein

A

the sequence of amino acids in the polypeptide chain

26
Q

secondary structure of a protein

A

hydrogen bonds formed between the amino acids in the chain cause it to coil and fold into alpha helices or beta pleated sheet

27
Q

what bonds are formed in the tertiary structure of a protein

A

ionic

disulphide bonds

hydrogen bonds

28
Q

ionic bonds

A
29
Q

disulfide bonds

A
30
Q

quaternary structure

A

multiple polypeptide chains assembled together

31
Q

features of globular proteins

A

round, compacts made of multiple polypeptide chains

chains coiled up so hydrophilic parts of chain on the outside of the molecule so its soluble in water as it creates hydrogen bonds with it making it easier to be transported around

32
Q

example of globular protein

A

haemoglobin

33
Q

features of fibrous proteins

A

long, insoluble polypeptide chains that are tightly coiled round each other to form rope shape

chains held together by lots of bonds making it strong so hence they are found in supportive tissue

34
Q

example of fibrous protein

A

collagen

35
Q

what determines the active site of an enzyme shape

A

tertiary structure determined by primary

36
Q

how does substrate concentration affect rate of a reaction up to a point

A

the higher the substrate concentration, the faster the reaction (more substrate molecules available so collision between substrate and enzyme is more likely and so more active sites are used)

after a saturation point, there are too many substrate molecules (all active sites are full) do adding more makes no difference

substrate concentration decreases over time so rate of reaction decreases

37
Q

give two reasons why the formation of enzyme-substrate complex lower activation energy

A

if enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in substrate so substrate molecule breaks up more easily

if two substrate molecules need to be joined, being attached to the enzyme holds them close together reducing any repulsion between molecules so they can bond more easily

38
Q

function of DNA

A

stores genetic information which is all the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult

39
Q

function of RNA

A

transfer genetic information from DNA to ribosomes where proteins are made

40
Q

what makes up a mononucleotide

A

pentose sugar

nitrogen-containing organic base

phosphate group

41
Q

polynucleotides

A

polymer of mononucleotides joined together through condensation reaction between phosphate of one and sugar of other

42
Q

how many hydrogen bonds form between A and T

A

2

43
Q

how many hydrogen bonds form between C and G

A

3

44
Q

triplet

A

sequence of three bases that codes for amino acid

45
Q

messenger RNA

A

made in nucleus during transcription

codon (three adjacent bases)

carries generic code from DNA in nucleus to cytoplasm where its used to make a protein during translation

46
Q

transfer RNA

A

found in cytoplasm

has an amino acid binding site at one end and anticodon on the other

carriers amino acids used to make proteins to ribosomes during translation

47
Q

non-overlapping code

A

when base triplets dont share their bases

48
Q

degenerate genetic code

A

more possible combinations of triplets than there are amino acids so some amino acids are coded for more than one triplet

49
Q

start codon

A

where production of protein starts

50
Q

stop codon

A

where production of protein stops

51
Q

what enzyme is involved in transcription

A

RNA polymerase

A Level Biology : Content (18 decks)

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