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SNAB A Level Biology > Topic 2 : Genes and Health > Flashcards

Topic 2 : Genes and Health Flashcards

1
Q

why do organisms with low SA:V ratio need specialised gas exchange surfaces

A

bc diffusion alone is not sufficient

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2
Q

3 features of an efficient gas exchange surface

A

1) large surface area
2) thin/short distance
3) steep concentration gradient

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3
Q

what is Ficks law? Give the corresponding equation.

A

increased SA and greater conc grad increase the rate of diffusion.
thicker diffusion distances reduce the rate of diffusion

diffusion distance

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4
Q

how are mammal lungs adapted for gas exchange?

A
  • Alveoli provide a large SA
  • Good blood supply = maintains steep conc grad
  • one cell thick = short diffusion distance
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5
Q

structure of cell membrane

A
  • phospholipid bilayer
  • channel proteins
  • carrier proteins
  • glycoproteins
  • glycolipids
  • cholesterol
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6
Q

why is it called a fluid mosaic model?

A

Cell membranes are fluid and have a mosaic like arrangement

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7
Q

what evidence led to development of fluid mosaic model?

A
  • microscopes show proteins on membrane surface
  • lipid soluble substances pass more easily in and out of cells than water soluble
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8
Q

define osmosis

A

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

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9
Q

what is passive transport

A

movement of particles down a conc grad, no energy required

diffusion, facilitated diffusion and osmosis

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10
Q

define diffusion

A

net movement of small, non-polar, lipid-soluble molecules from an area of high conc to an area of low conc.

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11
Q

define facilitated diffusion

A

movement of polar, charged, water-soluble particles from high to low conc through a carrier protein or channel protein

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12
Q

define active transport

A

movement of molecules against a conc grad
energy in the form of ATP is required. Also uses carrier proteins.

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13
Q

what is the process of endocytosis

A

cell membrane forms a vesicle and engulfs the substance, which enters the cytoplasm

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14
Q

what is endocytosis used for

A

to bring large molecules into the cell

eg proteins
lipids
some carbohydrates

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15
Q

what is the process of exocytosis

A

vesicle forms from the Golgi apparatus and moves towards the cell membrane. Vesicle fuses with cell membrane to release contents from cell

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16
Q

what is exocytosis used for

A

to secrete substances produced by the cell eg hormones, some enzymes, and lipids

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17
Q

how are nucleotides formed

A

via a condensation reaction forming phosphodiester bonds

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18
Q

what is DNA made up of?

A

phosphate, deoxyribose sugar, and a nitrogenous base : adenine, thymine, guanine and cytosine.

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19
Q

What is RNA made up of?

A

phosphate, ribose sugar, and a nitrogenous base : adenine, uracil, guanine and cytosine

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20
Q

what are the 2 structural forms of a nitrogenous base?

A

purine or pyrimidines

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21
Q

what are purines… and what bases are purines

what are pyrimidines… and what bases are pyrimidines

A

purines = double ring structure
eg adenine and guanine

pyrimidines = single ring structure
eg cytosine, thymine and uracil

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22
Q

how are the antiparallel dna strands bonded

A

the complimentary bases are hydrogen bonded together

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23
Q

properties of RNA

A

single stranded
uracil base instead of thymine
ribose sugar
relatively short

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24
Q

different types of RNA

A

tRNA
mRNA
rRNA

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25
Q

What is a gene?

A

a sequence of nucleotide bases in dna that codes for the production of specific amino acids

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26
Q

what is transcription?

A

when dna is transcribed and an mRNA molecule is produced

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27
Q

what is translation

A

mRNA is translated to the cytoplasm and an amino acid sequence is produced

28
Q

what happens during transcription

A

DNA helicase unzips and the hydrogen bonds between the bases break

free activated RNA nucleotides pair up with their base pairs on the antisense strand …. making the RNA strand

catalysed by RNA polymerase

29
Q

where does transcription occur

A

nucleus

30
Q

where does translation occur

A

cytoplasm

31
Q

what happens during translation

A

mRNA leaves the nucleus and attaches to a ribosome

tRNA molecules bind with their specific amino acids in the cytoplasm and bring them ribosome

tRNA anticodon pairs with the codon on the mRNA

amino acids attached to the tRNA form peptide bonds and primary structure.

Translation is caused by a start and a stop codon.
The code is non overlapping and degenerate.

32
Q

what does a non overlapping and degenerate code mean?

A

non overlapping = each codon codes only for a particular amino acid i.e each code is only read once

degenerate = an amino acid can be produced from different triplets of bases.

33
Q

how many amino acids are there?

A

20

34
Q

what is the general structure of an amino acid?
draw it

A

amine group = NH2
Carboxyl group = COOH
Hydrogen and R group

H H O
N - C - C
H R OH

35
Q

what is the name of the bond that forms between amino acids?

A

peptide bonds

36
Q

what atoms are lost from the amino acids to form a peptide bond

A

OH of one COOH group
H from the amine group of another amino acid

37
Q

in what reaction are peptide bonds formed, what are the products

A

condensation reaction… 1 water molecule

38
Q

in what reaction are peptide bonds broken?

A

hydrolysis, add one molecule of water

39
Q

what is the primary structure of a protein

A

sequence of amino acids bonded together by peptide bonds

40
Q

what is the secondary structure of a protein

A

chain coils into an alpha helix
H bonds form between every 4th peptide bond
or
folds into a beta pleated sheet
two parts of the pp chain are parallel + form H bonds w each other

41
Q

what is the tertiary structure of a protein

A

additional bonds forming between R groups

42
Q

what bonds form and where in a tertiary structure

A

H bonds between R groups
Disulphide bonds between cysteine amino acids
Ionic between charged R groups
Hydrophobic and Hydrophilic interactions between non polar R groups

43
Q

what is a quaternary structure

A

when more than one polypeptide chain is involved

44
Q

describe globular and fibrous proteins… give examples of each one

A

globular = compact, spherical, soluble. HAEMOGLOBIN
GCSS - garry can suck sally

fibrous = long crosslinked chains, insoluble, little to no tertiary structure COLLAGEN

45
Q

why do globular proteins form a spherical shape in their tertiary structure

A

non polar hydrophobic R groups are towards the centre of the protein

polar hydrophilic R groups are towards the outside

46
Q

why are globular proteins soluble…what does this allow them to do ?

A

soluble b/c orientation of the R groups… water molecules can surround the polar hydrophilic R groups

solubility means they can be easily transported around organisms and involved in metabolic reactions

47
Q

what is the structure of haemoglobin?

A

quaternary structure… 4 polypeptide chains… 2 alpha globin and 2 beta globins each with a prosthetic haem group

the four globin chains are held together by disulphide bonds

each haemoglobin can carry 4 oxygen molecules b/c each haem group contains Fe2+

48
Q

properties of haemoglobin

A
  • binds to O2 in the lungs and transports to tissues for aerobic respiration

O2 not very soluble so HG allows it to be carried more efficiently around the body

existence of Fe2+ in the haem group allows for O2 to bind reversibly. Amino Acids unable to bind to oxygen

49
Q

properties of fibrous proteins

A
  • insoluble and strong
    suitable for structural roles
  • rarely ever tertiary structures
50
Q

what is collagen

A

a fibrous structural protein

forms:
tendons, cartilage, ligaments, bones, teeth, skin, cornea

51
Q

structure of collagen

A

3 polypeptide chains held together by hydrogen bonds to form a triple helix

covalent bonds form cross-links between R groups

collagen molecules are positioned in the fibrils… many fibrils form fibres = collagen fibres

52
Q

function of collagen

A

forms protective tissues
many H bonds = great tensile strength
staggered ends within collagen molecules in the fibrils = strength
collagen = stable b/c the many proline and hydroxyproline repel eachother

53
Q

what is the role of enzymes

A

biological catalysts, speed up rate of reactions by reducing activation energy

can be intracellular or extracellular

54
Q

structure of enzymes

A

globular proteins with complex tertiary structures

sometimes quaternary

55
Q

what are intracellular and extracellular enzymes

A

intracellular = produced and function inside of the cell
extracellular = secreted by the cell and function outside

56
Q

what conditions cause an enzyme to denature

A

extreme temp / pH

57
Q

what conditions are needed for an enzyme-substrate complex to form

A

substrates must collide with active site at the correct orientation and speed

58
Q

what does the induced-fit hypothesis state about how enzymes work?

A

enzyme and substrate interact w each other
- enzyme + active site can change shape slightly as substrate enters the enzyme

  • these changes AKA conformational changes
    they ensure ideal binding arrangement and maximises the ability of the enzyme to catalyse
59
Q

what is the name of the process in which DNA is replicated?

A

semi conservative replication

60
Q

why is DNA replication process called “semi conservative”

A

in each new DNA molecule, one strand has conserved the original DNA and then used this to create a new strand

61
Q

why is it important to retain one original DNA strand

A

it ensures there is genetic continuity between generations of cells
important as cells are replaced regularly … we need the new cells to carry out the same roles as the old ones

62
Q

when does DNA replication occur

A

in preparation for mitosis in the S phase of the cell cycle

63
Q

what is the process of DNA replication?

A

enzyme helicase unwinds the double helix by breaking the hydrogen bonds between the base pairs.

each single polynucleotide strand acts as a template for the formation of a new strand made from free nucleotides that are attracted to the exposed dna bases

the new nucleotides are then joined together.
The OG strand and new strand join together via H bonding between base pairs.

64
Q

what enzyme is involved in joining the new nucleotides together

A

dna polymerase

65
Q

what are the free nucleotides that contain 3 phosphate groups called?

A

nucleotide triphosphates or activated phosphates

SNAB A Level Biology (3 decks)

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