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a level biology > Topic 2: Genes and Health part 1 > Flashcards

Topic 2: Genes and Health part 1 Flashcards

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1
Q

properties of gaseous exchange surfaces in living organisms

A

large surface area
thin, short diffusion pathway
steep concentration gradient thanks to a good blood supply

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2
Q

what is different about the mucus of CF sufferers and how does it affect gaseous exchange

A

it has less water
this makes it sticky and harder for the cilia to move it
increased diffusion distance in alveoli
and, more chance of lung infections
gaseous exchange is less efficient overall

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3
Q

where is the mucus in the gaseous exchange system produced

A

its produced continuously from goblet cells in airway walls

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4
Q

what is the purpose of the mucus in your gaseous exchange system

A

it traps any dust, debris or micro-organisms that enter the airway

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5
Q

what is Fick’s Law

A

rate of diffusion ∝ surface area x concentration difference / thickness of exchange surface

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6
Q

what factors are not taken into account by Fick’s Law

A
  1. membrane composition
  2. size and nature of the diffusing molecule (big, small, charge)
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6
Q

what are the effects of CF on the lungs and so, gaseous exchange

A
  • the sticky mucus can be drawn into the alveoli since it isn’t cleared away - may increase exchange surface thickness
  • sticky mucus in bronchioles - may block narrow airways and stop alveoli ventilation, decreasing surface area and the concentration gradient , the blockages may also cause over inflation of lung tissue
  • mucus not being swept away can lead to recurring lung infections that can weaken the lungs and lead to a gentler concentration gradient
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7
Q

what is an epithelium

A

it is a tissue where epithelial cells work together, it consist of 1/more cell layers on a basement membrane

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8
Q

what makes up a basement membrane

A

protein fibres in a jelly like matrix

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9
Q

list 2 types of epithelia

A
  1. squamous epithelia
  2. columnar epithelia
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10
Q

what are ciliated epithelial cells

A

cells found in the trachea, bronchi and bronchioles that beat and move substances along the tubes they line

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11
Q

what are the main biological functions of proteins

A
  • as enzymes
  • carrier proteins - transport molecules across membranes
  • antibodies
  • structural proteins - support tissues and cells
  • hormones
  • transport proteins - proteins that carry other molecules (eg. haemoglobin)
  • contractile proteins enable muscle contraction
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12
Q

how many amino acids are there

A

20 natural amino acids, 8 of which are essential and can’t be synthesised by the body

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13
Q

what is the general structure of an amino acid

A
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14
Q

how do you form a polypeptide/peptide bond

A

condensation reaction between a carboxyl and amine group

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15
Q

what is the primary structure of a protein

A

the sequence of amino acids, held together by peptide bonds that are formed by a condensation reaction (loss of water)

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16
Q

what is the secondary structure of a protein

A

weak hydrogen bonds form between nearby amino acids in the chain (but there are many of them making it strong)
the polypeptide chain is no longer flat and straight as this automatically coils it into an alpha helix or folds it into a beta pleated sheet

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17
Q

describe an alpha helix

A

hydrogen bonds form between certain peptide bonds, this causes them to coil and form a stabilized shape

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18
Q

describe a beta pleated sheet

A

several adjacent amino acid chains are linked together by hydrogen bonds, holding the parallel chains close together

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19
Q

what is the tertiary structure of a protein

A

the beta pleated sheet/alpha helix is often Further folded or coiled, more bonds (ionic/disulfide bonds) form between 2 parts of the polypeptide chain

if the protein was made from a single polypeptide chain, the tertiary structure will be their final 3D structure

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20
Q

what are ionic bonds in a tertiary structure

A

the weak attraction between positive+negative charges on different parts of the molecule
they form when 2 R-groups have opposing charges

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21
Q

what are disulfide bonds in a tertiary protein structure

A

bonds that form between two sulfur atom containing R-groups

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22
Q

how is the eventual 3D structure of a protein determined

A

by it’s amino acid sequence (primary structure) as that determines what bonds will be formed in the tertiary (3D) structure - the 3D structure then determines properties

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23
Q

how do hydrophilic and hydrophobic side chains affect the structure of a protein

A

hydrophobic (water-repelling) groups tend to clump together in the protein. so, hydrophilic (water-attracting) groups are more likely to be pushed to the outside

this affects how the protein will fold up and the final structure it forms

24
Q

what is the quaternary structure of a protein

A

it can only be formed by proteins made of several different polypeptide chains held together with bonds, this is the final structure for proteins with more than 1 polypeptide chain

25
Q

outline characteristics of fibrous proteins

A

formed from parallel polypeptide chains, held together by cross-links which give high tensile strength
- long, rope-like fibres
- mostly insoluble in water
- sequences and chain length vary slightly between examples of the same protein
stable structure, regular+repetitive amino acid sequences
eg. keratin and collagen

26
Q

outline the structure of globular proteins

A
  • formed from tightly folded polypeptide chain - spherical shape
  • water soluble - they’re usually folded so that hydrophobic groups are inside and hydrophilic groups are on the outside and so can perform in metabolic reactions
  • highly specific sequence and chain length - never varies between 2 examples of the same protein
  • irregular amino acid sequences, relatively unstable structure

eg. all enzymes, some hormones, transport proteins

27
Q

functions of membranes

A
  • keep all cellular components inside the cell
  • allow movement of selected molecules in and out of the cell
  • isolate organelles from the rest of the cytoplasm (allows cellular processes to occur separately)
  • provides a biochemical reaction site
  • allows a cell to change shape
28
Q

combining fat and water

A

water and dietary lipids don’t mix, because water is polar and fats are non-polar
so fats don’t form hydrogen bonds with water

as fats are hydrophobic, they lie on the surface of water to reduce the surface area in contact between the water and the fat

29
Q

what are phospholipids

A

they are the lipids found in the cell membrane
composed of: a glycerol backbone, 2 non-polar fatty acid chains, one polar phosphate group

the hydrophilic bits associate with water and the hydrophobic bits repel water

30
Q

what is the structure of a cell membrane and it’s characteristics

A

it’s mostly made up of a phospholipid bilayer and proteins which can move in the fluid-mosaic model

characteristics:
1. allows lipid-soluble substances to pass through
2. prevents water-soluble substances from passing through
3. it is flexible

31
Q

phospholipids in water

A

orientates so that the polar, phosphate head is ON the water

32
Q

role of phospholipids in a cell membranes

A

provide a barrier to hydrophilic/water soluble substances, eg. ions + charged molecules

forms the phospholipid bilayer which has all the components embedded and is the fundamental basis of the cell membrane

33
Q

role of cholesterol in a cell membrane

A

helps maintain fluidity of membrane

  1. acts as spacers between phospholipids when temps are too low to prevent stiffening
  2. functions to connect phospholipids when temps are too high to prevent it becoming too fluid
34
Q

role of protein and glycoprotein in a cell membrane

A

they form channels that hydrophilic substances can pass through; the channels can be opened + closed

act as transporters that use active transport to move substances across the membrane

act as receptor sites; allow specific molecules from outside the cell (eg. hormones) to bind with them + then set up responses within the cell

act as recognition sites; their precise structure may be specific to a particular cell/individual

act as enzymes

35
Q

define diffusion

A

the net movement of particles from an area of higher concentration to an area of lower concentration, it is a passive process

36
Q

what is facilitated diffusion

A

the way in which larger polar molecules (eg. glucose/amino acids) and ions diffuse through carrier/channel proteins in the cell membrane

37
Q

what is a channel protein

A

a protein that provides a functional pore/channel in the membrane for charged particles to pass through

different channel proteins facilitate the diffusion of different charged particles

38
Q

what are carrier proteins

A

proteins that act as a specific carrier molecule in the membrane

39
Q

how does a carrier protein work

A
  1. a large molecule such as glucose/amino acids attaches itself to a carrier protein in the cell membrane
  2. the protein changes shape
  3. this releases the molecule on the opposite side of the membrane
40
Q

define osmosis

A

the net movement of water molecules from a solution with a high water concentration to a low water concentration through a partially permeable mebrane

41
Q

define active transport

A

the movement of a substance across a membrane, against the concentration gradient

42
Q

how were different cell membrane models discovered

A

through the analysis of data

43
Q

devise an experiment to investigate the permeability of a cell membrane

A
  1. cut 5 1cm3 pieces of beetroot using a scalpel on a cutting board, rinse to remove any pigment released when cutting
  2. measure 5cm3 of water into 5 different test tubes using a measuring cylinder
  3. place empty test tubes into water baths at 10˚C, 20˚C, 30˚C, 40˚C, 50˚C
  4. add the beetroot to each of the test tubes for 5 minutes again (time with a stopwatch)
  5. remove the beetroot, leaving just the coloured liquid
  6. switch on the colorimeter and give it 5 minutes to stabilise, set it up so that you are using a blue filter and calibrate it to 0 using pure water
  7. use a pipette to transfer one of your betroot tubes into a clean cuvette, 3/4 full
  8. put it in the calorimeter and record the absorbance
  9. repeat for the other beetroot solutions, using clean cuvettes and pipettes

the higher the absorbance, the more permeable the membrane is because less light passed through the solution

44
Q

how does temperature affect membrane permeability

A

below 0 - phospholipids are packed together closely and the membrane is rigid, channel proteins and carrier proteins in the membrane deform and increase permeability; ice crystals can form and make the membrane highly permeable by piercing it when it thaws

0-45 - phospholipids can move around and aren’t as tightly packed together; partially permeable
phospholipids move more as temp increases, increasing membrane permeability

45+ - phospholipid bilayer starts melting and breaking down, increasing permeability, water inside the cell expands and puts pressure on the membrane, carrier and channel proteins deform, increasing permeability

45
Q

how does alcohol concentration increase membrane permeability

A

alcohol dissolves lipids in the cell membrane, making it lose it’s structure

46
Q

compare and contrast globular vs fibrous proteins

A
  • both have amino acid chains joined by peptide bonds
  • both have Hydrogen bonds
  • globular has a compact shape and fibrous is long chains
  • fibrous has hydrophobic groups on the outside (insoluble)and globular has hydrophilic groups on the outside
  • globular have tertiary/quaternary structure and fibrous have little/no tertiary structure
47
Q

why does mucus have less water in cystic fibrosis

A

chloride and sodium ions can’t get through the cell membrane and enter the mucus, so water moves out of the mucus via osmosis

48
Q

what does a glycoprotein do in the cell membrane

A

cell recognition

49
Q

what is endocytosis

A

vesicles are formed from the cell membrane so that large molecules can enter the cell

50
Q

how was the cell membrane decided to be fluid mosaic

A
  • EM pics used to show 3 layers in a cell membrane but they improved and showed a bilayer of phospholipids
  • new protein analysis methods showed they were distributed randomly rather than a continuous layer
  • experiments proved its fluidity; a mouse and human cell were fused and the membrane proteins completely intermixed throughout the membrane
51
Q

outline the structure of collagen

A

primary structure is a repeating amino acid sequence
it’s made of three polypeptide chains coiled around each other with cross-linking between the chains

52
Q

what units do things have to be in for Fick’s law?

A

doesn’t matter xxxx just use whatever is given ?!!!!

53
Q

why are identical twins studied

A

they have the same genotypes so any differences will be due to environmental factors

54
Q

outline facilitated diffusion

A

substances like large, polar molecules (glucose and amino acids) and ions can only cross the phospholipid bilayer with the help of transport proteins, this is facilitated diffusion

the two transport protein types that enable facilitated diffusion are channel and carrier proteins and they are highly specific, allowing just one type of molecule of ion to pass through

55
Q

outline channel proteins

A
  • pores that extend through the membrane from one side to the other
  • they allow a specific charged substance to diffuse through the cell membrane
  • this diffusion doesn’t occur freely and most channel proteins are ‘gated’, aka the part of the channel protein on the inside of the membrane can move to close or open and control the exchange of ions
56
Q

outline carrier proteins and facilitated diffusion

A

carrier proteins can switch between two shapes
a large molecule attaches to the carrier protein and causes a change in the proteins shape and this releases the molecule on the opposite side of the membrane

57
Q

outline active transport

A

a molecule attaches to the carrier protein and the protein changes shape which moves the molecule across the membrane and releases it on the other side

ATP produced from respiration is hydrolysed to release energy as an immediate energy source

a level biology (13 decks)

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