CBS Flashcards

1
Q

SER function?

A

Biosynthesis of lipids and sterols
n-linked glycosylation
detox of xenobiotics
(functions are tissue specific)

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2
Q

RER function?

A

Protein synthesis and protein folding

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3
Q

Cytoplasm function?

A

aqueous solution with precise pH and ion composition

site of metabolic reactions

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4
Q

Nucleus function?

A

site of genetic material, replication and transcription

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5
Q

Plasma membrane function?

A

boundary for cell, selective transport and signalling

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6
Q

Golgi body function?

A

modification and packaging of proteins for export/sub-cellular compartments

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7
Q

Lysosome function?

A

autophagy and cell turnover

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8
Q

Peroxisome function?

A

detoxification, phospholipid synthesis, production and degradation of hydrogen peroxide and long chain fatty acid oxidation

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9
Q

Mitochondria function?

A

ATP synthesis, TCA and fat oxidation

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10
Q

Cytoskeleton function?

A

mechanical strength, controls cell shape, guides cell movement

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11
Q

What is chromatin?

A

DNA organised into chromosomes -> a complex of DNA, histones and other proteins

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12
Q

Nucleous function?

A

rDNA transcription, ribosome subunit assembly

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13
Q

Which organelles are visible by light microscopy?

A

nucleus and mitochondria

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14
Q

What are the 4 main classes of biomolecules?

A

carbohydrates, nucleic acids, proteins and lipids

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15
Q

Which orientation is alpha and beta glucose?

A

alpha has OH group facing down, beta has it facing up

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16
Q

How are glycosidic bonds formed?

A

2 monosaccharides are joined by glycosyltransferase

Produces disaccharide and water

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17
Q

What makes up the 3 disaccharides?

A
sucrose = glucose + fructose
maltose = glucose + glucose
Lactose = glucose + galactose
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18
Q

What is the basic nucleotide structure?

A

phosphate group + pentose sugar + base

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19
Q

What is the structure and function of triacylglycerol?

A

3 fatty acids + glycerol

energy storage in adipose tissue

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20
Q

what are the structures of protein?

A

primary structure = amino acid sequence
secondary structure = a-helix and b-sheets
tertiary structure = 3d folding of polypeptide
quaternary structure = subunit assembly

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21
Q

What are the different type of amino acid side chain interactions?

A

disulphide bridges, hydrogen bonds, ionic bonds, van der Waals forces, hydrophobic effect

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22
Q

What are class 1 enzymes - oxoreductases

A
  • add o2 or remove 2H

- e.g. lactate dehydrogenase

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23
Q

What are class 2 enzymes - transferases

A
  • transfer functional groups

- e.g. alanine amino transferase

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24
Q

What are class 3 enzymes - hydrolases

A
  • catalyse hydrolytic reactions

- e.g. tripsin

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25
Q

What are class 4 enzymes - lysases

A
  • add groups to C-C bonds

- e.g. ATP-citrate lysase

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26
Q

What are class 5 enzymes - isomerases

A
  • catalyse isomerisation

- e.g phosphoglycose isomerase

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27
Q

What are class 6 enzymes - ligases

A
  • form new covalent bonds using ATP

- e.g. DNA ligase

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28
Q

What are isoenzymes?

A

different enzymes that catalyse the same reaction

e.g. lactate dehydrogenase

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29
Q

What is the michaelis menton constant?

A

Km = (K-1 + K2)/ K1

low Km = high affinity

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30
Q

What is the michaelis-menton equation?

A

V0 = Vmax[S] / (Km + [S])

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31
Q

What are the assumptions of the michaelis-menton equation?

A
  1. there is much more [S] than [E]
  2. ES formation = ES breakdown (steady-state)
  3. Inital velocities are used
32
Q

What can you find from a michaelis-menton plot?

A
Vmax = max height of graph 
Km = 1/2 Vmax
33
Q

How is efficacy of an enzyme calculated?

A

Kcat/Km

34
Q

What values of Kcat and Km do you want for an enzyme?

A

High Kcat

Low Km

35
Q

What is the lineweaver-burke plot used for?

A

to determine Km & Vmax experimentally

36
Q

What does a lineweaver-burke plot indicate?

A
1/Vmax = y-intercept
-1/Km = x-intercept
37
Q

How do inhibitors alter Km/Vmax?

A

Competitive alter Km (increase it)

Non-competitive inhibitors decrease Vmax

38
Q

what is pH

A

meaasure of H+ concentration

= -log[H+]

39
Q

what is the pH range in blood?

A

7.35-7.45

40
Q

what is the living range of pH?

A

7.0-7.8

41
Q

what is the pH range in urine?

A

5.0-8.0

42
Q

what is a buffer?

A

a solution that resists large swings in pH by releasing H+ or accepting H+

43
Q

what is pKa?

A

the pH where half the acid is dissociated

= -log[Ka]

44
Q

what is the henderson-hasselbach equation?

A

pH = pKa + log[A-]/[HA]

45
Q

what is the main buffer in blood?

A

haemoglobin (due to histamine residues)

46
Q

what is the pKa of haemoglobin?

A

oxy Hb = 6.8

deoxy Hb = 7.8

47
Q

What is the structure of a phospholipid?

A

polar head (serine, choline etc), phosphste group, glycerol backbone, 2 fatty acid chains

48
Q

What factors affect membrane fluidity?

A

chain lengths - short chains increase fluidity
saturation - more double bonds increase fluidity
cholesterol - decreases fluidity

49
Q

How can integral proteins be removed from a membrane?

A

by detergent

50
Q

How can anchored proteins be removed from a membrane?

A

by detergent and phospholipases

51
Q

How can peripheral proteins be removed from a membrane?

A

by detergent, phospholipase or high salt solution

52
Q

What is the structure of haemoglobin?

A

tetrameric haem protein

2 alpha and 2 beta chains

53
Q

What is the structure of foetal haemoglobin?

A

2 alpha and 2 gamma chains

54
Q

What proteins are targeted via the ER?

A

lysosomal, membrane and secreted proteins

55
Q

What proteins are translated in the cytosol?

A

nuclear, mitochondrial and peroxisomal proteins

56
Q

What are the steps of protein synthesis in the ER?

A
  1. ribosome initiates synthesis
  2. SRP recognises the signal sequence on protein
  3. SRP binds receptor on ER membrane
  4. Protein is guided through translocon into ER lumen
  5. Signal sequence is cleaved
57
Q

How do vesicles fuse with membranes?

A

V-SNARE on vesicle binds with T-SNARE on membrane

58
Q

What moleucle is required for targeting proteins to the mitochondria?

A

Chaperones e.g. HS70

59
Q

What directs protein targeting to the nuclues?

A

Nuclear localisation signal (NLS) binds to importin

60
Q

How does protein targeting to the lysosome occur?

A

proteins are tagged with mannose-6 phosphate
receptor on golgi directs proteins into vesicles
vesicle matures into lysosome

61
Q

What is a disease affecting lysosomes?

A

I-cell disease

mannose 6 phosphate mutation

62
Q

what are the units of actin?

A
filaments = f-acint
monomers = g-actin
63
Q

What is the structure of actin?

A

double helix with a positive and negative end

64
Q

How do actin filaments grow?

A

g-actin is added and removed at each end

binds ATP to be added

65
Q

What are some examples of intermediate filaments?

A

lamina, keratin, neurofilaments

66
Q

What is the structure of microtubules?

A

long, stiff hollow tubes

made of alpha and beta tubulin monomers

67
Q

What affects the rate of diffusion?

A

Kow - partition coefficient

68
Q

How do ions move through an ion channel?

A

selectivity filter - hydration shell which is sensitive to the ion’s radius

69
Q

What are the features of GLUT1?

A
low Km (high affinity) 
mainly in RBCs and BBB
70
Q

What are the features of GLUT2?

A

high Km
in pancreatic beta cells and hepatocytes
triggers insulin release

71
Q

What are the features of GLUT3?

A

low Km

in neurones

72
Q

What are the features of GLUT4?

A

in muscle and adipocytes

insulin binding triggers GLUT4 to move to plasma membrane

73
Q

What is GLUT5?

A

fructose transporter

74
Q

What is a drug that inhibits the Na+/Ca2+ transporter

A

ovabain

used in heart failure - triggers contraction

75
Q

What is SGLUT1?

A

Na+/glucose transporter
used to absorb glucose in intestines
targeting in cholera therapy

76
Q

What is the signalling pathway involving PLC?

A

Gq -> PLC -> DAG + IP3
IP3 opens Ca2+ channels in the ER
DAG and Ca2+ activate PKC