Biochemistry Flashcards
1
Q
What is the structure of RNA?
A
Phosphate Group
5-carbon Sugar
Nitrogenous base (A+U) & (C+G)
Single helix
2
Q
What is the structure of DNA?
A
Phosphate Group
5-carbon Sugar
Nitrogenous base (A+T) & (C+G)
Double helix
3
Q
What is the sugar in DNA?
A
Deoxyribose
4
Q
What is the sugar in RNA?
A
Ribose
5
Q
What is the bonding between guanine and cytosine?
A
3 hydrogen bonds
6
Q
What is the bonding between adenine and thymine?
A
2 hydrogen bones
7
Q
What are the differences in nitrogenous bases between RNA and DNA?
A
RNA has uracil
DNA had thymine
8
Q
How are nucleotides jointed together to make a chain?
A
Sugar phosphate backbones of phosphodiester bonds
9
Q
What is the process of DNA Replication?
A
- Helicase enzyme splits DNA helix into replication fork
- Giving leading and lagging strand
- RNA primase on lagging strand + synthesising DNA in small fragments via DNA polymerase = Okazaki fragments (3 to 5 prime)
- RNA primers removed by DNA polymerase and replaced with DNA on lagging strand
- DNA Ligase completes replication of lagging strand
10
Q
What are the 4 enzymes used in DNA replication?
A
Helicase
RNA primase
DNA polymerase
Ligase
11
Q
What are Okazaki fragments?
A
Short sequences of DNA synthesised by RNA primer on the lagging strand
12
Q
What is the process of RNA Transcription
A
- Promoter region of DNA to tell RNA polymerase where to start
- RNA polymerase separates strands of DNA into coding & template strand
- RNA polymerase encodes RNA onto template strand of DNA
- Synthesised 3 to 5 prime
- Stops once hits terminator region = pre-mRNA made - Introns spliced out, only exons left
- Poly-A tail on the 3’ prime end - Now is mature mRNA
13
Q
What happens with mature mRNA in translation?
A
- mRNA sent from the nucleus to the ribosome
- Every 3 nucleotides of mRNA = codon (each codon encodes for amino acids)
- tRNA matches to mRNA via anti-codon, with amino acid attached
- Peptide bond forms between amino acids
- Polypeptide released = protein made
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
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.
16
Q
What are proteins?
A
Chain of amino acids bound by peptide bonds and folded into its protein shape
17
Q
Which amino acid does not exist as 2 isomers?
A
Glycine
18
Q
Which isomer do amino acids tend to exist as in the body?
A
L isomers
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
20
Q
What is proteins primary structure?
A
Linear sequence of the order of amino acids
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)
22
Q
How are secondary protein structures stabilised?
A
Hydrogen bonds
23
Q
How is tertiary protein folding stabilised?
A
Stabilised by hydrogen bonds, VDW interaction, hydrophobic packing, disulphide bridge
24
Q
What is quaternary protein folding?
A
Bonding between multiple polypeptides
Each chain is called a subunit
25
What are 5 types of proteins?
```
Globular - haemoglobin, albumin
Fibrous proteins - collagen
Motor proteins - myosin
Soluble proteins - immunoglobulins
Membrane proteins - receptors
```
26
How does serum protein electrophoresis work and why is it done?
Separates proteins based on size and charge to identify proteins in the blood
27
What is the mutation in sickle cell anaemia and what is the outcome?
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
28
What affect do enzymes have on reactions?
Lowers the activation energy
Speed up the reaction
Enzyme remains unchanged
Exothermic product remains the same
29
What factors can alter the rate of successful collisions of enzymes in a reaction?
Proximity and orientation
30
What does enzyme activity depend on?
Temperature
pH
Substrate concentration
31
What is Vmax?
The maximum rate once all the enzymes have been saturated.
Substrate concentration will no longer affect the reaction
32
What is Km?
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.
33
What is competitive inhibition?
- 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
34
What is non-competitive inhibition?
- 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
What are cofactors?
Non-protein substances required for an enzymatic reaction to proceed.
ATP, NADH, Coenzyme A...
36
What is the problem with enzymes being denatured?
Disruption in the bonds and folding of the amino acids means substrate can no longer fit in the active site.
37
What is the role of enzymes in diagnosis and management of disease?
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
What are the functions of lipids?
Key components of cell membranes
Major form of energy storage
Important role in cell signalling
39
What is the structure of fatty acids?
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
What are triglycerides made from?
Glycerol and Fatty acids
41
What is the function of triglycerides?
It is the storage form of lipids - stored in adipose tissue as SC fat and visceral fat
42
How are triglycerides absorbed?
Cannot be absorbed whole
Need to break up into glycerol and fatty acids
Fatty acid absorbed in the blood as albumin complex
43
What are 3 functions of cholesterol?
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
What is the structure of cholesterol?
4 ring structure
| Weakly amphiphilic
45
What is the function of Glycerophospholipids?
Main component of cell membranes.
Reabsorbed in digestive tract, first emulsified by bile and then cleaved by phospholipases of the pancreas
46
What is the structure of glycerophosphoplipids?
Fatty acid hydrophobic chain
Glycerol
Phosphate and alcohol polar head group
Alcohol can be serine, choline, ethanolamine... - changes the form of the lipid
47
What is the structure of sphingomyelin?
Fatty acid
Sphingosine
Phosphate
Choline
48
What sphingolipids are components of cell membranes in nerve tissues and the brain?
Sphingomyelin, cerebroside, ganglioside
49
What is lysosomal storage disease?
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
What are examples of peptide hormones and where are they stored?
Glucagon, oxytocin, insulin, FSH, ADH, PTH
Stored in vesicles
51
What are properties of peptide hormones?
Both hydrophilic and lipophobic
Need membrane receptors to get through lipid membranes into cells - mediate cell signalling with second messengers - cAMP
52
What are examples of steroid hormones and where are they synthesised from?
Cortisol, testosterone, oestrogen, progesterone
Synthesised from cholesterol in the adrenal cortex
Released immediately into the blood stream
53
What are examples of amino-acid derived hormones and what are they synthesised from?
Adrenaline, Thyroxine, Dopamine, Melatonin
Synthesised from amino acid tyrosine and tryptophan
Stored before release
54
What are properties of amino-acid derived hormones?
Hydrophilic and lipophillic
55
What are examples of lipid hormones and what are they synthesised from?
Leukotrienes, Prostacyclin, Prostaglandins, Thromboxane
Synthesised from fatty acids
Act in paracrine and autocrine manner but not hormones
56
What is autocrine hormone transport?
Local cell-cell diffusion, act on neighbouring cells of same type
57
What is paracrine hormone transport?
Local cell-tissue diffusion, act on different cells in same tissue
58
What is endocrine hormone transport?
Distributed by blood, act on distant target cells
59
How does ion channel work?
Hormone binds to ion channel
Ion channel opens = ion moves in = cell depolarisation
e.g. serotonin, GABA
60
How do Guanlyl Cyclase coupled Receptors work?
Hormone binds to receptor = conformational change of GC
| GTP converted into cGMP = activation of protein kinases
61
How does receptor kinases work?
Hormone binds to receptor and triggers intrinsic activity of kinase receptor
Receptor phosphorylates proteins by converting ATP to ADP
62
What are the 2 steroid pathways to transduce a signal?
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
What is Addisons disease?
Deficiency of adrenal hormones – adrenal glands
64
What is Cushing syndrome?
Overproduction of ACTH - pituitary, cortisol – adrenal glands – long term steroid use
65
What is achondroplasia?
Deficiency of growth hormone
66
How do G-protein coupled receptors work?
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
Name 3 monosaccharides.
Glucose
Fructose
Galactose
68
What is the disaccharide maltose made from?
2 glucose molecules
a(1-4)-glycosidic bond
69
What is the disaccharide sucrose made from?
Glucose and fructose
a(1-2)b-glycosidic bond
70
What is the disaccharide lactose made from?
Glucose and galactose
b(1-4)-glycosidic bond
71
What is cellulose made up of?
B1-4 linked glucose molecules
72
What is starch made up of, what is the branched and unbranched molecule called?
Made up of glucose
If unbranched = amylose
If branched = amylopectin
73
What is an alpha isomer of a sugar?
The hydroxyl of the first carbon atom and hydroxymethyl group are pointing on the same side of the molecule
74
What is a b isomer of a sugar?
The hydroxyl of the first carbon group and hydroxymethyl group are pointing on the opposite sides of the molecule
75
Name 3 polysaccharides.
Cellulose
Starch
Glycogen
All made from glucose monomers
76
What is the role of glucose in glycolysis?
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
What is the role of glucose in the pentose phosphate pathway?
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
How is fructose absorbed into the intestinal mucosa?
GLUT-5 transporter
79
How are carbs transported from the intestinal mucosa into the blood?
GLUT-2 transporter
80
How is glucose and galactose absorbed into the intestinal mucosa?
SLGT-2 transporter
81
What is galactosaemia?
Deficiency in the enzyme that can break down galactose, leading to the accumulation of galactose which is oxidised and reduced to toxic metabolites
82
What are symptoms of undigested carbs and why do they occur?
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
What does amylase break down?
Starch into maltose and dextrin
In saliva and pancreas
