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YEAR 1 > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

What is the structure of RNA?

A

Phosphate Group
5-carbon Sugar
Nitrogenous base (A+U) & (C+G)

Single helix

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2
Q

What is the structure of DNA?

A

Phosphate Group
5-carbon Sugar
Nitrogenous base (A+T) & (C+G)

Double helix

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3
Q

What is the sugar in DNA?

A

Deoxyribose

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4
Q

What is the sugar in RNA?

A

Ribose

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5
Q

What is the bonding between guanine and cytosine?

A

3 hydrogen bonds

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6
Q

What is the bonding between adenine and thymine?

A

2 hydrogen bones

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7
Q

What are the differences in nitrogenous bases between RNA and DNA?

A

RNA has uracil

DNA had thymine

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8
Q

How are nucleotides jointed together to make a chain?

A

Sugar phosphate backbones of phosphodiester bonds

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9
Q

What is the process of DNA Replication?

A
  1. Helicase enzyme splits DNA helix into replication fork
  2. Giving leading and lagging strand
  3. RNA primase on lagging strand + synthesising DNA in small fragments via DNA polymerase = Okazaki fragments (3 to 5 prime)
  4. RNA primers removed by DNA polymerase and replaced with DNA on lagging strand
  5. DNA Ligase completes replication of lagging strand
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10
Q

What are the 4 enzymes used in DNA replication?

A

Helicase
RNA primase
DNA polymerase
Ligase

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11
Q

What are Okazaki fragments?

A

Short sequences of DNA synthesised by RNA primer on the lagging strand

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12
Q

What is the process of RNA Transcription

A
  1. Promoter region of DNA to tell RNA polymerase where to start
  2. RNA polymerase separates strands of DNA into coding & template strand
  3. RNA polymerase encodes RNA onto template strand of DNA
  4. Synthesised 3 to 5 prime
    - Stops once hits terminator region = pre-mRNA made
  5. Introns spliced out, only exons left
  6. Poly-A tail on the 3’ prime end - Now is mature mRNA
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13
Q

What happens with mature mRNA in translation?

A
  1. mRNA sent from the nucleus to the ribosome
  2. Every 3 nucleotides of mRNA = codon (each codon encodes for amino acids)
  3. tRNA matches to mRNA via anti-codon, with amino acid attached
  4. Peptide bond forms between amino acids
  5. Polypeptide released = protein made
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14
Q

What enzymes are used in RNA transcription?

A

RNA polymerase

transcription factors bind to promoter regions to bring RNA polymerase to the site

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15
Q

What are the 5 structural components of an amino acid?

A

Central carbon

Amino group
Carboxylic acid group
Hydrogen group
Unique group different for each AA.

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16
Q

What are proteins?

A

Chain of amino acids bound by peptide bonds and folded into its protein shape

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17
Q

Which amino acid does not exist as 2 isomers?

A

Glycine

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18
Q

Which isomer do amino acids tend to exist as in the body?

A

L isomers

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19
Q

How is a peptide bond formed?

A

Nucleophilic reaction between 2 amino acids of the carboxyl and amino group

Elimination of water

Exists in rigid planar bond

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20
Q

What is proteins primary structure?

A

Linear sequence of the order of amino acids

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21
Q

What is secondary structure folding of proteins?

A

How the linear sequences folds on each other.

Alpha Helix:
- Coil like structure
Beta-pleated Sheets:
- Zigzag structure
- Exist in parallel sheets (amide ends line up + carboxyl ends line up) or…
- Exist in antiparallel sheets (amide lines up with carboxyl end)

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22
Q

How are secondary protein structures stabilised?

A

Hydrogen bonds

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23
Q

How is tertiary protein folding stabilised?

A

Stabilised by hydrogen bonds, VDW interaction, hydrophobic packing, disulphide bridge

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24
Q

What is quaternary protein folding?

A

Bonding between multiple polypeptides

Each chain is called a subunit

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25
Q

What are 5 types of proteins?

A 
Globular - haemoglobin, albumin
Fibrous proteins - collagen
Motor proteins - myosin
Soluble proteins - immunoglobulins
Membrane proteins - receptors
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26
Q

How does serum protein electrophoresis work and why is it done?

A

Separates proteins based on size and charge to identify proteins in the blood

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27
Q

What is the mutation in sickle cell anaemia and what is the outcome?

A

Single point mutation in DNA leading to change in amino acid from glutamine to valine = changes protein structure

Red blood cells shapes become distorted, cannot move through capillaries well - slower blood flow and low oxygen delivery

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28
Q

What affect do enzymes have on reactions?

A

Lowers the activation energy
Speed up the reaction
Enzyme remains unchanged
Exothermic product remains the same

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29
Q

What factors can alter the rate of successful collisions of enzymes in a reaction?

A

Proximity and orientation

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30
Q

What does enzyme activity depend on?

A

Temperature
pH
Substrate concentration

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31
Q

What is Vmax?

A

The maximum rate once all the enzymes have been saturated.

Substrate concentration will no longer affect the reaction

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32
Q

What is Km?

A

The substrate concentration at which the reaction rate is 50% of the Vmax.

Km is a measure of the affinity an enzyme has for its substrate, as the lower the value of Km, the more efficient the enzyme is at carrying out its function at a lower substrate concentration.

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33
Q

What is competitive inhibition?

A
  • Inhibitor binds to the active site of the enzyme
  • Inhibitor can be displaced by substrate if high substrate conc
  • Inhibitor causes an increase in Km ( more substrate needed to saturate enzyme)
  • Vmax remains unchanged
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34
Q

What is non-competitive inhibition?

A
  • Inhibitor binds to a allosteric site other than the active site of the enzyme - causing a change to the tertiary structure - altering active site - substrate can no longer bind
  • Substrate concentration has no effect as active site shape has been altered
  • Reduction in reaction rate = Vmax decreases
35
Q

What are cofactors?

A

Non-protein substances required for an enzymatic reaction to proceed.

ATP, NADH, Coenzyme A…

36
Q

What is the problem with enzymes being denatured?

A

Disruption in the bonds and folding of the amino acids means substrate can no longer fit in the active site.

37
Q

What is the role of enzymes in diagnosis and management of disease?

A

Physical or functional damage to cells may release enzymes into the blood - use elevated activities of certain enzymes in the plasma for tissue markers and diagnostics.

38
Q

What are the functions of lipids?

A

Key components of cell membranes
Major form of energy storage
Important role in cell signalling

39
Q

What is the structure of fatty acids?

A

Hydrocarbon chain with a carboxyl group

  • Saturated - single carbon bonds
  • Monounsaturated - 1 double carbon bond - plant oils, liquid at room temp
  • Polyunsaturated - more than 1 double carbon bond - liquid at room temp
40
Q

What are triglycerides made from?

A

Glycerol and Fatty acids

41
Q

What is the function of triglycerides?

A

It is the storage form of lipids - stored in adipose tissue as SC fat and visceral fat

42
Q

How are triglycerides absorbed?

A

Cannot be absorbed whole
Need to break up into glycerol and fatty acids

Fatty acid absorbed in the blood as albumin complex

43
Q

What are 3 functions of cholesterol?

A

Essential structure of cell membranes
Precursor for steroids and hormones
Synthesised into bile acids to emulsify fats

HmG-CoA reductase is key for cholesterol synthesis

44
Q

What is the structure of cholesterol?

A

4 ring structure

Weakly amphiphilic

45
Q

What is the function of Glycerophospholipids?

A

Main component of cell membranes.

Reabsorbed in digestive tract, first emulsified by bile and then cleaved by phospholipases of the pancreas

46
Q

What is the structure of glycerophosphoplipids?

A

Fatty acid hydrophobic chain
Glycerol
Phosphate and alcohol polar head group

Alcohol can be serine, choline, ethanolamine… - changes the form of the lipid

47
Q

What is the structure of sphingomyelin?

A

Fatty acid
Sphingosine
Phosphate
Choline

48
Q

What sphingolipids are components of cell membranes in nerve tissues and the brain?

A

Sphingomyelin, cerebroside, ganglioside

49
Q

What is lysosomal storage disease?

A

Inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate

Neimann-Park disease - sphingomyelin
Farber’s limo-granulomatosis - ceramide
Tay Sachs disease - ganglioside
Gaucher’s disease - glucocerebroside

50
Q

What are examples of peptide hormones and where are they stored?

A

Glucagon, oxytocin, insulin, FSH, ADH, PTH

Stored in vesicles

51
Q

What are properties of peptide hormones?

A

Both hydrophilic and lipophobic

Need membrane receptors to get through lipid membranes into cells - mediate cell signalling with second messengers - cAMP

52
Q

What are examples of steroid hormones and where are they synthesised from?

A

Cortisol, testosterone, oestrogen, progesterone

Synthesised from cholesterol in the adrenal cortex

Released immediately into the blood stream

53
Q

What are examples of amino-acid derived hormones and what are they synthesised from?

A

Adrenaline, Thyroxine, Dopamine, Melatonin

Synthesised from amino acid tyrosine and tryptophan

Stored before release

54
Q

What are properties of amino-acid derived hormones?

A

Hydrophilic and lipophillic

55
Q

What are examples of lipid hormones and what are they synthesised from?

A

Leukotrienes, Prostacyclin, Prostaglandins, Thromboxane

Synthesised from fatty acids

Act in paracrine and autocrine manner but not hormones

56
Q

What is autocrine hormone transport?

A

Local cell-cell diffusion, act on neighbouring cells of same type

57
Q

What is paracrine hormone transport?

A

Local cell-tissue diffusion, act on different cells in same tissue

58
Q

What is endocrine hormone transport?

A

Distributed by blood, act on distant target cells

59
Q

How does ion channel work?

A

Hormone binds to ion channel
Ion channel opens = ion moves in = cell depolarisation

e.g. serotonin, GABA

60
Q

How do Guanlyl Cyclase coupled Receptors work?

A

Hormone binds to receptor = conformational change of GC

GTP converted into cGMP = activation of protein kinases

61
Q

How does receptor kinases work?

A

Hormone binds to receptor and triggers intrinsic activity of kinase receptor
Receptor phosphorylates proteins by converting ATP to ADP

62
Q

What are the 2 steroid pathways to transduce a signal?

A

1st Pathway:

- Hormone diffuses into cell and binds to intracellular receptor in cytoplasm
- Hormone-receptor complex moves into nucleus

2nd pathway:
- Hormone diffuses into cell and moves in nucleus to bind to intracellular receptor in nucleus

63
Q

What is Addisons disease?

A

Deficiency of adrenal hormones – adrenal glands

64
Q

What is Cushing syndrome?

A

Overproduction of ACTH - pituitary, cortisol – adrenal glands – long term steroid use

65
Q

What is achondroplasia?

A

Deficiency of growth hormone

66
Q

How do G-protein coupled receptors work?

A

Hormone binds to membrane receptor which causes a conformational change of the G protein.
GDP exchanged to GTP on alpha subunit of G protein…

  1. GTP alpha subunit dissociates and binds to calcium channel
    • Calcium Channel opens and calcium moves inside
    • Alpha subunit hydrolyses GTP back to GDP = dissociation from calcium channel and reattaches to receptor + channel closes
  2. GTP alpha subunit dissociates and binds to…
    A. Adenyl Cyclase - convertes ATP into cAMP = activation or protein kinases
    B. Phospholipase C - breaks PIP2 into DAG and IP3 = activate protein kinases
67
Q

Name 3 monosaccharides.

A

Glucose
Fructose
Galactose

68
Q

What is the disaccharide maltose made from?

A

2 glucose molecules

a(1-4)-glycosidic bond

69
Q

What is the disaccharide sucrose made from?

A

Glucose and fructose

a(1-2)b-glycosidic bond

70
Q

What is the disaccharide lactose made from?

A

Glucose and galactose

b(1-4)-glycosidic bond

71
Q

What is cellulose made up of?

A

B1-4 linked glucose molecules

72
Q

What is starch made up of, what is the branched and unbranched molecule called?

A

Made up of glucose

If unbranched = amylose
If branched = amylopectin

73
Q

What is an alpha isomer of a sugar?

A

The hydroxyl of the first carbon atom and hydroxymethyl group are pointing on the same side of the molecule

74
Q

What is a b isomer of a sugar?

A

The hydroxyl of the first carbon group and hydroxymethyl group are pointing on the opposite sides of the molecule

75
Q

Name 3 polysaccharides.

A

Cellulose
Starch
Glycogen

All made from glucose monomers

76
Q

What is the role of glucose in glycolysis?

A

Glucose converted to pyruvate via glycolysis via aerobic respiration, 2 ATP and 2 NADH molecules.

Pyruvate put into the Krebs cycle for production of more ATP

77
Q

What is the role of glucose in the pentose phosphate pathway?

A

Conversion of glucose into Ribose-5 phosphate which is a precursor for nucleotides/DNA/RNA (non-oxidative)

Glucose also converted into NADPH, electron rich for anabolic reactions and antioxidant molecules (oxidative)

78
Q

How is fructose absorbed into the intestinal mucosa?

A

GLUT-5 transporter

79
Q

How are carbs transported from the intestinal mucosa into the blood?

A

GLUT-2 transporter

80
Q

How is glucose and galactose absorbed into the intestinal mucosa?

A

SLGT-2 transporter

81
Q

What is galactosaemia?

A

Deficiency in the enzyme that can break down galactose, leading to the accumulation of galactose which is oxidised and reduced to toxic metabolites

82
Q

What are symptoms of undigested carbs and why do they occur?

A

Undigested carbs pass into the large intestine - osmotic diarrhoea
Bacterial fermentation of carbs produces large volumes of CO2 and H2 which lead to abdominal cramps, flatulence, diarrhoea.

83
Q

What does amylase break down?

A

Starch into maltose and dextrin

In saliva and pancreas

YEAR 1 (17 decks)

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