Metabolism Flashcards
(259 cards)
1
Q
First law of thermodynamics and how it relates to metabolism
A
Total energy within a system in constant and energy can neither be created or destroyed but can be converted. This is how metabolism works- energy conversion
2
Q
Two parts of metabolism and main way which energy is converted in bodies via cellular reactions
A
Anabolism (ATP-> ADP/ Pi) energy breakdown
Catabolism (ADP/Pi-> ATP) energy buildup
3
Q
What does human energy intake equate to
A
Intake= E(expended) + E(stored)
4
Q
What is stored energy and how can it be lost
A
Weight/ weight gain
Can be lost by reducing energy intake, increasing activity and increasing BMR
5
Q
What is one Joule in relation to energy
A
The energy required to push against 1N of force to 1m.
Unit of energy
6
Q
How is energy expenditure measured
A
Calorimetry- sealed enclosed chamber system where combustion occurs and energy is measured
7
Q
Energy measurements of fat, carbs, proteins and ethanol
A
Fat- 37kJ/g
Carbs- 17kJ/g
Protein- 17kJ/g
Ethanol- 29kJ/g
8
Q
How is energy lost from food
A
In faeces and N isnt oxidised and is lost through urine
9
Q
Methods of measuring energy expenditure
A
Direct calorimetry
Indirect calorimetry
10
Q
How does direct calorimetry work
A
Relies on measuring heat output from an individual and is good at determining BMR at rest
11
Q
How does indirect calorimetry work
A
Based on O2 consumption and CO2 production using a respirometer. Allows calculation of energy expenditure for a range of activities and also allows for calculation of respiration exchange ratio (RER)
12
Q
What increases energy expenditure
A
Increase in activity
13
Q
How is RER measured
A
CO2 produced/ O2 consumed
14
Q
What is BMR and things used for
A
Energy required for maintenance of life eg muscle contractions, nerve conduction, ion transport, macromolecule synthesis and maintenance of body heat
15
Q
How does BMR differ
A
Differs between people, can be increased or decreased
16
Q
How is BMR increased
A
Athletic training, late stage of pregnancy, fever, drugs such as caffeine, hyperthyroidism
17
Q
How is BMR decreased
A
Malnutrition, sleep, drugs eg beta-blockers, hypothyroidism
18
Q
What are the macronutrients and what are they broken down into
A
Carbs -> monosaccharides
Protein -> amino acids
Nucleic acids -> nucleotides
Fat -> FFAs, MAG, cholesterol
19
Q
Parts of G.I tract and what they secrete to digest macronutrients
A
Salivary glands- amylase in mucous for carbs
Stomach- HCL secreted, pepsinogen for proteins, mucous for protection
Pancreas- most digestive enzymes (amylase, lipase, proteases)
Liver- bile salts and acids for fat
Small Intestine- other digestive enzymes (maltase, lactase, sucrase, isomaltase, aminopeptidase, dipeptidase)
20
Q
Two phases of digestion
A
Hydrolysis of bonds connecting monomer units in food macromolecules
Absorption of products from GI tract into body
21
Q
Features of carb digestion
A
Provides 40-50% of energy intake
Starch, simple sugars and fibre from carbs
Bonds broken are glycosidic bonds
22
Q
Enzymes involved in carb digestion and what they hydrolyse
A
Salivary and pancreatic amylase- starch Maltase- maltose Lactase- lactose Sucrase- sucrose Isomaltase- isomaltose
23
Q
How are carbs digested/ order of digestion
A
Starch alpha(1-4) hydrolysed in mouth and by pancreas to oligosaccharides then to maltose/ isomaltose Digestion of disaccharides at brush border in small intestine Monosaccharides absorbed into body
24
Q
Features of protein digestion
A
Supplies amino acids to make body proteins
Source of N for purines, pyrimidines, haem
C-skeletons used as fuel
Excess N-> urea excreted from urine
Hydrolysis of peptide bonds
25
Essential amino acids to be obtained from the diet (8)
Leucine, lysine, threonine, tryptophan, isoleucine, methionine, phenylalanine, valine
26
What is kwashiokor and what are consequences of it
Deficiency of dietary protein= osmotic imbalance in GI tract= abdomen swells (oedema) due to water retain.
Albumin level in blood lowered affecting colloidal osmotic (oncotic) pressure and transport of molecules (hormones and drugs)
27
What are proteases
They break down peptide bonds. Initially secreted as zymogens/ proenzymes and activated by cleavage of peptides.
Specificity determines by adjacent amino acid side chains (pepsin aromatic, trypsin positive charge, chymotrypsin aromatic)
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Stages of protein digestion
Endopeptidases- attack peptide bond within polymer (pepsin, trypsin, chymotrypsin)
Exopeptidases- attack peptide bond at end of protein polymer (aminopeptidases, carboxypeptidases)
29
Enzymes involved in protein digestion and what they hydrolyse
Pepsin- proteins and pepsinogen in stomach
Trypsin- polypeptides and chymotrypsinogen in small intestine
Chymotrypsin- polypeptides in small intestine
Carboxypeptidase- polypeptides in small intestine
Aminopeptidase- polypeptides in small intestine
Dipeptidase- dipeptides in small intestine
30
What is pepsinogen and how is it activated
Inactive form/ zymogen of pepsin. Activated from exposure to HCl in stomach and secreted into stomach via chief cells
Part of pepsinogen unfolds and activates pepsin protease= hydrolysis of pepsinogen
31
What zymogens/ proenzymes are released from the pancreas and how are they activated
Procarboxypeptidase- activated to carboxypeptidase
Chymotrypsinogen- activated to chymotrypsin by trypsin
Trypsinogen- activated to trypsin by membrane-bound enterokinase
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Order of protein digestion
```
Pepsin in stomach
Trypsin in small intestine
Chymotrypsin in small intestine
Carboxypeptidase in small intestine
Aminopeptidase in small intestine
End products= amino acids, di- and tri-peptides
```
33
Molecules associated with fat metabolism
Triacylglycerol (TAG) and cholesterol ester
34
Where is bile acid/ bile salts made, where is it stored, how is it secreted and what does it do once secreted
Synthesised from cholesterol in liver
Stored in gall bladder as bile
Secreted into SI in response to cholecystokinin
Has detergents with hydrophibis and hydrophilic surfaces and forms micelles with TAGs to increase SA for digestion
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Bile contents
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Water
Bile acids (glycocholic acid and taurocholic acid)
Electrolytes
Phospholipids
Cholesterol
Bile pigments eg bilirubin
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36
What is a result of too much cholesterol in the gall bladder
Gall stones
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Hormones involved in fat digestion
Gastrin
Secretin
Cholecystokinin
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Gastrin source, stimulus of production and actions
Stomach, protein-containing food in stomach and para-sympathetic nerves to stomach and stimulates secretion of gastric juices
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Secretin source, stimulus of production and actions
Duodenum, HCl in duodenum, stimulates secretion of alkaline bile and pancreatic fluids
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Cholecystokinin source, stimulus of production and actions
Duodenum, fats and amino acids in duodenum, stimulates release of pancreatic enzymes and bile from gall bladder
41
Outline of lipid digestion process (up to absorption in intestine)
Lipids emulsified by bile salts from micelles
Pancreatic lipase/ colipase enzyme system binds to lipid/ aqueous interface of micelle and hydrolyses TAGs
Pancreatic lipase hydrolyses fatty acids at positions 1 and 3 of glycerol backbone of TAG
Smaller micelles form containing bile salts, free fatty acids, monoacylglycerol and cholesterol
Micelles are absorbed across the intestinal cell membrane
42
What causes efficient absorption by the small intestine
Villi and microvilli increasing SA
43
What happens once micelles are in the small intestine
Micelle goes to smooth ER and becomes TG
TG + apoB+ phospholipids go to the golgi where they become chylomicrons
Chylomicrons are released into lymph system and go to blood
44
What causes fat malabsorption, what is it caused by and what is used to help it
Caused by conditions that interfere with bile or pancreatic lipase and causes excess of fat and fat soluble vitamins in faeces.
Xenical (orlistat) is a patent inhibitor of pancreatic lipase which forms a covalent bond to lipase and prevents it from hydrolysing TAG so it is less taken up by the GI tract
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What are lipoproteins
They solubise lipids for transport in the blood to tissues (delivery system)
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Apoprotein functions
Structural for assembly (apoB)
Ligands for cell surface receptors (apoB and apoE)
Enzyme cofactors (apoCII for lipoprotein lipase)
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Different lipoprotein classes
Chylomicrons
Very low density (VLDL)
Low density (LDL)
High density (HDL)
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What are the two lipid transport pathways
```
Exogenous chylomicron (dietary fat)
Endogenous VLDL/LDL (endogenously synthesised fat)
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How does the exogenous lipid transport pathway work
Chylomicrons-> blood
Free fatty acids leave blood stream and go to tissue and muscle
Remnants in blood go to the liver via the apoE receptor
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How does the endogenous lipid transport pathway work
VLDL leaves the liver -> blood
Free fatty acids leave blood and go to tissue and muscle
Remnants B100-> peripheral tissues and E-> liver
LDL B100-> peripheral tissues also
51
Features of lipoprotein lipase
Enzyme found on endothelial surface
Hydrolyses TAG in lipoproteins to glycerol and fatty acids highest activities in heart and skeletal muscle and adipose tissue
Activated by apoCII
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What does a defect/ mutation in lipoprotein lipase or apoCII lead to
Elevated levels of chylomicrons and plasma tricylglyerol
53
How can LDL be estimated
[total cholesterol - HDL - triglyceride/5]
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How can VLDL be estimated
[triglyceride/5]
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Units for LDL and VLDL in NZ
mmol/L
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Two inherited lipid disorders to know and where they come from
In VLDL processing- defect in apoCII= familial apoCII deficiency
In VLDL remnant clearance- defect in LDL receptor= familial hypercholesterolaemia (FH)
57
What is familial hypercholesterolaemia, what causes it and what is used to treat it
Common form of hyperlipidaemia= premature atherosclerosis
Caused by defect/ mutation in LDL receptor
Dominant disorder
LDL levels are 2-3x higher than normal
Causes xanthomas= fatty growths under the skin surface
Treated with statins
58
What do statins do
Lower LDL (bad cholesterol) and increase HDL (good cholesterol)
59
How to know if someone has high blood triglyceride and how is it treated
Milky liquid in blood plasma from centrifuge and treated with tricor (fenofibrate)
60
why cant sugars/ carbs diffuse through cells
They are highly water soluble
61
Two types of transport involved in sugar and protein transport
Active transport with ATP
| Facilitative transport down a concentration gradient
62
Two important transporters for glucose in the small intestine
SGLT-1 secondary active transporter
| GLUT-2 facilitative transporter
63
Other glucose transporters and where they are located
GLUT-2 also in liver, pancreas and kidney
GLUT-3 in brain
GLUT-4 in muscle and adipose tissue
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What glucose transporter is a drug target and what does it help against
GLUT-1 effective against renal cell carcinoma
65
How are di- and tri- peptides absorbed into the small intestine
Co-transport with H+ via membrane transporter PepT1
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How are di-and tri- peptides further digested and exported
Digested into individual amino acids by cytoplasmic peptidases and exported from epithelial cells into blood circulation
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How are amino acids absorbed
From lumen by transepithelial transport
68
How does transepithelial transport work
Semispecific Na-dependent carriers transport Na and amino acids into epithelial cells.
Amino acids transported to portal veins by facilitated transporter and Na is pumped out with ATP-ase
69
How is glucose absorbed
SGLT-1 co-transports glucose and Na into epithelial cells
GLUT-2 transports glucose out of epithelia
ATP-ase controls Na inside cells
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What are the different types of Na-dependent carriers
Neural amino acids
Proline and hydroxyproline
Acidic amino acids
Basic amino acids lysine, arginine and cistine
71
When are intact proteins absorbed from the GI tract
In a few circumstances eg newborns take up immunoglobulins in colostral milk for passive immunity
72
Different diseases leading to issues in carb and amino acid absorption
Lactose intolerance- lactase enzyme deficiency
Pancreatitis- inappropriate activation of zymogens
Stomach ulcers- breakdown of mucosa
Cystic fibrosis- malabsorption
Coeliac disease- malabsorption
73
How does cystic fibrosis cause malabsorption and how can it be helped
Thick mucous secretions block pancreatic duct and secretion of pancreatic enzymes.
Can be aided by taking supplements containing pancreatic enzymes eg pancreatin= pancreas extract
74
How does coeliac disease cause malabsorption
Disease of small intestine where body reacts against gluten in wheat. Antibodies react with transglutaminase and causes flattened villi so nutrients aren’t absorbed. Causes gastrointestinal symptoms
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How are dietary nucleic acid polymers digested
DNA and RNA subject to partial hydrolysis from acidic conditions
Intestinal endonuclease enzymes hydrolyse phosphodiester bonds linking nucleotides
Exonuclease enzymes release individual nucleotides as nucleoside monomers
Individual nucleotides absorbed with nucleotide transporters
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4 ways to tell if someone is getting enough vitamins and minerals
Clinical examination- look for symptoms
Anthropornetry- energy balance/ growth
Biochemical tests
Dietary assessments- measure what you eat, convert into nutrients and compare with nutrient reference values
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6 characteristics of vitamins
‘Vital to life’/‘vital amines’
Essential, individual organic molecules
Dont provide energy when broken down
If absent or low in the diet, symptoms of deficiency appear
Required in diet in small amounts (micro grams or mg)
Bioavailability= amount absorbed and used
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Fat soluble vitamins
A, D, E, K
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Water soluble vitamins
C and B (B1, B2, B3, B5, B6, B7, B9, B12)
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Roles of vitamins and minerals
Coenzymes and cofactors
Structural
Antioxidants
DNA/RNA
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Functions of vitamins
Mainly all B- vitamins involved in energy metabolism/ other metabolic pathways
B9 and B12 involved in DNA and RNA synthesis
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What vitamin deficiency causes niacin deficiency
B3
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What forms are B3 in for niacin deficiency
In form of nicotinic acid or nicotinamide. Tryptophan can be converted into nicotinamide
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Source of B3
Meats, liver, milk, fish, legumes and wheat
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What does niacin deficiency cause and how
Pellagro from NAD deficiency as NAD involved in oxidation and reduction and synthesis/ breakdown of carbs, lipids and amino acids
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Effects of pellagro
Leads to rash and 4 D’s (dermatitis, diarrhoea, dementia and death)
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5 characteristics of minerals
Essential and non-organic elements (eg Ca, Mg, Na)
Dont provide energy
If absent/ low deficiency symptoms may appear
Required in diet in small amounts
Bioavailability= amount absorbed and used
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Roles of minerals (many different)
```
Cofactors- electron transfer
Structural- hydroxyapatite crystal
Key constituent of many molecules
Nerve impulse and muscle contraction
Fluid and electrolyte balance
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89
What is magnesium thought to do and what was found out
Stabilises proteins, nucleic acids and membranes
Electrolyte
Bone metabolism and remodelling
Nerve impulse and muscle contraction
Thought to help against cramps
Found it has no benefit towards cramps
90
what is ATP known as in reactions
Major energy intermediate
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Which ATP reaction is spontaneous/ favourable
Hydrolysis. ATP-> ADP + Pi
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What part of metabolism is ATP hydrolysis associated with
Anabolism
| Cellular work; precursors -> products
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What part of metabolism is ATP synthesis involved in
Catabolism
| Fuel molecule breakdown eg glucose and O2 -> CO2 and H2O
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What does reaction coupling do and what molecules create coupled reactions in the body and why
Couples an unfavourable/ non-spontaneous and favourable/ spontaneous reaction to allow necessary unfavourable reactions to occur. Enzymes do it in the body to drive the necessary unfavourable reactions
95
Example of a coupled reaction in the body
Glycolysis
Glucose + phosphate -> glucose-6-phosphate + H2O
ATP + H2O -> ADP + Pi
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Two reaction types for energy conversion
Involving ATP/ADP
| Redox reactions
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Features of redox reactions
Oxidised molecule becomes more positive/ loses e-
Reduced molecule has a reduced positive charge/ gains e-
Energy is released during redox so are spontaneous as G<0
This released energy is captured for ATP production
98
What are coenzymes
Transfer H atoms = H+ and e-
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What is hydrogen known as in terms of cofactors and what does it mean
Reducing equivalent. Acts as reducing agent in biological redox reactions
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What are enzymes that catalyse biological redox reactions called
Dehydrogenases
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Features of co-enzymes (6)
```
Subclass of co-factors
Small organic molecules
Often derived from vitamins
Low concentration in cells
Act as carriers
Exist in 2 forms
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Three examples of coenzymes in the body where are they derived from and what are their 2 forms
NAD from niacin (vit B3), NAD and NADH
FAD from riboflavin (vit B2), FAD and FADH2
Coenzyme A (CoA) from pantothenic acid (vit B5), free CoASH and Acyl-CoA/ AcCoA
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Features of CoA different to other coenzymes
Not a carrier of e- so not involved in redox
| Carry acyl groups (carbon chain molecules)
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Features of glucose as a fuel molecule
6 carbon molecule
Oxidised in glycolysis
In mammals, all cells use glucose as fuel
Some cells rely on or preferentially use glucose
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Relationship between blood and glucose
Glucose is essential for RBCs as they dont have mitochondria so lack other pathways and rely on glycolysis
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The brain and glucose
Favoured fuel in the brain as brain has high energy requirement (~120g)
Supply- glucose easily crosses the blood-brain barrier and fats dont
Safety- high level of fatty acid metabolism is dangerous so relying on mitochondrial reactions risks anoxia (low O2) and production of reactive O2 species= damaging
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Glucose and the eye
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Favoured fuel in the eye
Blood vessels (bringing O2) and mitochondria would refract light in the optical path (lens, cornea) to retina
```
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Glucose and muscle cells
White use glucose (sprinting exercises)
| Red use fats (endurance exercises)
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Two phases of glycolysis
Energy investment phase= activation of glucose, getting the molecule into a form so energy can be converted
Energy payoff phase= return on the investment, making an ATP profit
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Purpose of the splitting/ aldose reaction
Convert 1x 6C molecule with 2x P -> 2x 3C molecules with 1x P each
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How does arsenic poison glycolysis
Arsenate (AsO4 3-) substitutes PO4 3-
Means an unstable arsenate hydrolysed by energy that isnt captured and ATP isnt synthesised by phosphoglycerate kinase
= no net gain of ATP
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What does rearrangement in glycolysis lead to
3PG -> 2PG-> PEP
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Overall glycolysis reaction and overall G°’
Glucose + 2NAD+ + 2ADP + 2Pi -> pyruvate + 2NADH + 2ATP + 2H+
overall G°’= -73.3kJ/mol
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What happens to pyruvate in aerobic conditions
Pyruvate -> acetyl-CoA in mitochondrial matrix
| Energy is captured in NADH and sed to add coenzyme CoA
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What happens to pyruvate in anaerobic conditions
Pyruvate -> lactate where NADH is oxidised to NAD+
| This allows for regeneration of NAD+ for glycolysis
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What does anaerobic pyruvate reaction to lactate cause and why does it occur
As energy in NADH is lost lactate causes muscle fatigue
Occurs because there is a low concentration of coenzymes in cells and during aerobic oxidation coenzymes are oxidised in oxidative phosphorylation
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Features of fatty acids as fuel molecules
Preferred fuel for most tissues
Fuels movements most of the time
Primary energy reserve in mammals as TAGs
5-25% of body weight
Excess energy consumed as glucose is stored as fat
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Why do we store fuel as fat
Fatty acids are more reduced then carbs so more energy is released when oxidised in pathways
Stored carb (glycogen) is 2/3 water so is polar
Less space needed to store ‘x’ amount of fuel as fat than same ‘x’ amount as glycogen
119
How are fatty acids delivered for fuel
Stored in adipose tissue
Passive transport into blood
Lipase breaks down TAG into free fatty acids
FFAs transported by albumin protein while in the blood
Passive transport out of albumin into tissues
Transported across cell membrane via fatty acid binding protein (facilitated transport or active transport)
120
Features of albumin transport protein
Hydrophobic core
| Hydrophilic exterior
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Fatty acids need to be activated for oxidation. Where and how does this occur
Occurs in cytosol before fatty acid enters the mitochondria
Activated by attachment to CoA to make fatty acyl-CoA
Energy from hydrolysis of ATP to AMP (energy cost = 2 ATP)
122
How are fatty acids transported into the mitochondrial matrix for oxidation
Passes through two membranes:
Outer membrane = fatty acyl-CoA carrier
Intermembrane space= fatty acyl-CoA-> fatty acyl-carnitine
Inner membrane= fatty acyl-carnitine carrier protein
Reverse carnitine acyl transferase reaction occurs in matrix to convert back to fatty acyl-CoA
123
How does B-oxidation work/ features of B-oxidation
Uses fatty acids with an even number of carbons that are saturated (no double bonds)
No ATP made- energy released is transferred to coenzymes NAD+ and FAD
Cuts carbon chains into two pieces
Product (acetyl-CoA) is further oxidised in the citric acid cycle
124
What happens in reactions 1-3 of B-oxidation
Involve rearrangement and energy is captured in two redox reactions and chemistry around the C-C bond is altered so that it can be easily cleaved in reaction 4
Go from C=C to C=O
|
C
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What happens in reaction 4 of B-oxidation
Is a cleavage where acetyl-CoA is released and CoASH is added to a carbon chain and shorter fatty acyl-CoA enters the next cycle/ next round of B-oxidation
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What is produced from each round/ cycle of B-oxidation
1 NADH, 1FADH2, 1 acetyl-CoA
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What is the equation that tells how many rounds a carbon molecule will undergo in B-oxidation
No. of rounds= n(C)/2 - 1
*an extra acetyl-CoA is always made (so if there is 7 rounds, there will be 7 products of NADH and FADH2 and 8 products of acetyl-CoA)
128
Features of the citric acid cycle and other names
Other name- tricarboxylic acid (TCA) cycle or krebs cycle
Occurs in mitochondria
All occurs in the matrix except for one enzyme which is bound to the inner membrane
Start and finish with the same molecule
2C in as acetyl-CoA, 2C out as CO2
Captures energy as ATP, NADH and FADH2
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How many redox reactions occur in the citric acid cycle
4
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Two parts of the citric acid cycle
Release of C
| Regeneration of starting molecule
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What happens in condensation of acetyl-CoA with oxaloacetate
2C enters as acetyl-CoA
They are attached to 4C oxaloacetate-> 6C citrate + CoASH
Energy released from hydrolysis of CoA from acetyl-CoA
132
What happens during isomerisation of citrate
Rearrangement of citrate to isocitrate= molecule now susceptible to decarboxylation
Both steps are catalyses by aconitase
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What is used to target the citric acid cycle to kill possums (for example) and how does it work
Fluoroacetate
Is it converted to a substrate irreversibly that binds tightly to aconitase and inactivates the enzyme
Fluorocitrate is made instead of citrate
Stops glycolysis and B-oxidation also as a result
134
How is the first carbon removed in the citric acid cycle
Oxidative decarboxylation
Occurs in two steps; oxidation then decarboxylation
Energy is captured in NADH in first step
Oxalosuccinate intermediate remains tightly bound to isocitrate dehydrogenase enzyme
Product is a-ketoglutarate
135
How does removal of the second carbon occur
Second oxidative decarboxylation
a-ketoglutarate converted to succinyl-CoA (4C molecule now)
Enzyme that does this is a-ketoglutarate dehydrogenase
Energy is captured in NADH
136
How does the conversion of succinyl-CoA to succinate achieved
Removal of CoA releases enough energy to drive GTP synthesis
GTP is energy equivalent of ATP
It is a third substate level phosphorylation
137
What is substrate level phosphorylation
Direct use of energy from a substrate molecule to drive synthesis of ATP or equivalent (such as GTP)
P doesn’t have to come from the substrate like the succinyl-CoA reaction
138
How does succinate to oxaloacetate occur
Rearrangement reactions
Succinate-> fumarate; FADH to FADH2
Fumarate-> malate; hydration
Malate-> oxaloacetate; NAD to NADH
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What is different about the succinate dehydrogenase enzyme in the citric acid cycle during oxaloacetate regeneration
It is located in the inner mitochondrial membrane
Uses FAD as a coenzyme
Part of the cycle where FAD is reduced so needs to be in the electron transport chain to oxidise FADH2-> FAD
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What is the overall citric acid cycle reaction
Acetyl-CoA + 3NAD + FAD + 2H2O + GDP + Pi -> 2CO2 + CoASH + 3NADH + 3H + FADH2 + GTP
141
What does the deamination of amino acids create
Carbon skeleton (R-C=O)
|
O
Free amino group (NH3+)
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What are the two methods of deamination of amino acids
Releasing amino groups into solution
Transfer of amino group to a keto acid via transamination
Both are reversible
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What catalyses each deamination of amino acid methods
Release into solution: glutamate dehydrogenase
| Transfer to keto acid: glutamate aminotransferase
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What is pyridoxal phosphate and its two forms
Coenzyme required for transamination reactions
Derived from VitB6
Carries amino group from amino acids to keto acids
Pyridoxal phosphate (no amino group)
Pyridoxamine phosphate (with amino group)
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Two steps in transamination
1- amino group transferred from amino acid to pyridoxal phosphate
2- amino group transferred from pyridoxamine phosphate to keto acid
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Amino acid and keto acid pairs in metabolism (movement from one to the other is reversible)
What can keto acids do in regards to metabolism
Glutamate and a-ketoglutarate (intermediate in CAC)
Asparate and oxaloacetate (start and end in CAC)
Alanine and pyruvate (end of glycolysis)
Keto acids can be fed into metabolic pathways (either enter directly or have modifications done first
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Brief overview of how NH3+ moves through the body
Muscle: NH3 from aa -> glutamate-> alanine
Liver: alanine-> glutamate -> NH3-> urea (from detoxification)
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Two parts of oxidative phosphorylation and how they relate to each other
electron transport chain and ADP-> ATP by ATP-synthase
Coupled reactions by a proton gradient
ETC makes the proton gradient and ATP-synthase uses the proton gradient
149
What experiment proves the electron transport chain happens in the inner mitochondrial membrane
1. Isolation of mitochondria (homogenisation in buffered sucrose of liver tissue, centrifuge at 1000 xg then supernatant at 7000 xg)
2. Take isolated mitochondria (treated with strong detergent solubilises all membranes, ECT doesnt work, treated with mild detergent solubilises outer membrane only, ECT works)
150
Overview of the electron transport chain
Electrons are passed through a series of carriers
Electrons from NADH and FADH2 are fed into the ECT (from oxidation)
Electrons then reduce O2-> water (as O2 is the terminal e- acceptor)
Protons are pumped as electrons are transported along ECT from the energy released
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What is the organisation of the ECT
Contains a series of complexes with electron carriers between
Complexes I-IV with multiple carriers
Two carriers are ubiquinone or coenzyme Q (UQ or CoQ) and cytochrome c (cyt c)
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What reactions occur to allow electrons to move through the ETC
Carriers undergoing series of redox reactions
Each carrier accepts electrons (is reduced) in one redox reaction
Reduced carriers then donate electrons (is oxidised) in another redox reaction
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What type of carriers do electrons like to move to and what does this mean for energy
Move to carriers with a higher reduction potential (O2 has highest) and energy is released along ECT meaning G°’ is negative
Energy released is used to translocate protons across the membrane
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Overview of how electrons flow through ETC
NADH - complex I- UQ- complex III- cyt c- complex IV- O2
| FADH2- complex II - UG - complex III- cyt c- complex IV- O2
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What are the inhibitors of electron flow in ETC
Rotenone- inhibits electron transfer from complex I to UQ
Cyanide- binds to carrier in complex IV
Carbon monoxide- binds where O2 binds
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What do the inhibitors do overall in ETC
Each stop electron flow through the ETC and no proton gradient is made so no ATP is made
Build-up of reduced coenzymes FADH2 and NADH= no oxidising power for other pathways
Reactive O2 species produced as O2 is partially reduced- causes damage to DNA, membranes etc
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What happens in complex I of ETC
NADH is oxidised= NAD+ feedback into other pathways
2 electrons are released into the ETC
4 H+ are pumped for each NADH oxidised with energy release
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What happens in complex II of the ETC
FADH2 is oxidised
SDH reaction occurs (shared with CAC)
2 electrons are released into the ETC
No protons are pumped
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How does UQ/CoQ work in the ETC and features of these coenzymes
Complex I and complex II electrons go to UQ
They can move within the inner mitochondrial membrane and move electrons to complex III which are released one at a time
They are coenzymes, not from vitamins- undergo two redox reactions and can accept or release one electron at a time
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What happens in complex III of the ETC
One electron released at a time into cyt c
| Pumps 4 protons across the inner membrane
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How does cyt c work in the ETC and features of the molecule
Moves on the outer surface of the inner membrane
Carries one electron at a time to complex IV
Has a heme containing protein which carries electrons by reversible Fe2+/Fe3+ redox reactions
162
How does complex IV work in the ETC and how does it work biologically
```
Accepts one electron at a time
Reduces O2-> H2O
For 1 NADH/FADH2 (2e-): 2 protons pumped
For 2 NADH/FADH2 (4e-): O2 + 4H+ -> 2H2O
Biologically- waits for 4 electrons from the oxidation of two coenzymes to do above reaction
```
163
Energy accounting in the ETC (how many protons are pumped)
NADH: 10 protons pumped
FADH2: 6 protons pumped
164
What is the proton motive force and what did Mitchell propose with it
The proton gradient across the inner mitochondrial membrane results in 2 energetic gradients
Chemical/ pH gradient- different H+ conc on either side of the membrane
Electrical gradient- charge difference across the membrane
Mitchell proposed energy from the pmf drives ATP synthesis
165
What does the electrical charge/ difference in charge result from
In the matrix and inter-membrane space, water exists as OH-, H2O and H3O+
In the inter-membrane space with H+ pumped into there is more H3O+ and in the matrix there is more OH- with lack of H+
166
Evidence supporting chemiosmotic coupling hypothesis
When mitochondria is isolated and treated with mild detergent, removing outer membrane, ETC works but ATP synthesis doesnt
Artificial liposome with ATP synthase makes ATP when light is switched on but there is no ETC present meaning only a proton gradient is needed for ATP synthesis
167
What does 2,4-dinitrophenol (DNP) cause and what is it as a result
Uncoupler that shifts H+ from intermembrane space to matrix, removing proton gradient
ETC functions, no ATP synthesis as pmf needed
DNP is a poison as energy isnt captured in ATP and is released as heat so body fries from the inside
168
How many mitochondria are there and how many ATP synthase per mitochondria? What does this mean
~200 mitochondria with ~200 ATP synthase each= heaps of energy being made
169
Parts of the F1F0-ATP synthase and where are they located
F1 in matrix
F0 in inner mitochondrial membrane
Has rotor subunits (actin filament, gamma tube and base with H+)
Has stator subunits (a/B, b2 and a)
170
How does F1F0- ATP synthase work
Proton flow in the base drives rotor movement leading to conformational change in stator a/B spaces from actin filament on top
171
How was it proved that ATP synthase rotated
Fluorescent actin filament on top
172
How do the conformational changes in ATP synthase a/B stator places in F1 cause ATP synthesis
O=open where release of ATP and binding of ADP + Pi occur
L=loose where ADP and Pi are held for catalysis
T=tight where ATP is catalysed and formed
173
How much ATP is made in ATP synthesis
```
NADH= 10 protons pumped= 2.5 ATP made
FADH2= 6 protons pumped= 1.5 ATP made
```
174
Effects of alcohol/ what does it do
Binds to the GABAa receptor (ligand gated Cl channel) where activation leads to selective conduction of Cl and inhibits effect of neurotransmission by reducing the chance of a successful action potential
Also damps down the responses to other stimuli
175
What is GABA lignad
GABA is a y-aminobutyrate neurotransmitter derived from glutamate
176
How much energy can be derived from ethanol
29kJ/g
177
How does absorption and elimination of alcohol occur
Ethanol-> acetaldehyde -> acetate-> acetyl CoA-> citric acid cycle
178
Enzymes in absorption and elimination of alcohol and energy conversions
```
Alcohol dehydrogenase (NAD->NADH)
Aldehyde dehydrogenase (NAD-> NADH)
Acetyl CoA synthetase (ATP-> AMP + PPi)
```
179
What is antabuse and what is it used for
Drug which inhibits aldehyde dehydrogenase so person feels sick from acetaldehyde build up and dont want anymore alcohol
180
What happens to acetyl CoA after alcohol absorption and main consequence
Can go to citric acid cycle, electron transport and oxidative phosphorylation to be turned into CO2 and ATP or become fatty acids. If there is too much fatty acids then VLDLs take away to store in adipose tissue causing fatty liver
181
What results from too much acetyl CoA with too much ATP and NADH and why does it happen
Slows citric acid cycle, electron transport and fatty acid oxidation
Shuts down pyruvate dehydrogenase and glycolysis
Fatty acids are esterfied to TAG= fatty liver, hypercholesterolaemia and hypertryacyglycerolaemia
Happens because the ethanol absorption pathway isnt shut down but other pathways are to stop excess ATP production
182
Consequences of too much acetyl CoA with too much NADH
Pyruvate-> lactate= decreased pH (like anaerobic conditions)
| Inhibits gluconeogenesis causing low blood sugar and can cause a coma
183
Other form of alcohol metabolism as a toxin
Microsomal ethanol oxidising system occurring in ER of the liver
Ethanol-> acetaldehyde from oxidase-> acetate from aldehyde dehydrogenase
NADPH+O2-> 2H2O and NAD-> NADH
184
Consequences of alternative metabolism of alcohol as a toxin
Also metabolises other drugs and sometimes adverse reactions can occur
Oxidase can give rise to reactive oxygen species
185
What does a persons weight mean in relation to amount of ATP used
Their weight is ~ATP used. Eg someone 70kg uses ~70kg of ATP (10,000kJ)
186
can ATP be used by the liver from the muscles when it runs out of its own? Why?
No. Because ATP isnt transferred between tissues, it is made in the tissue that needs it and when it is needed at the rate it is needed. ATP isnt an energy store
Fuels are stored (fat and glycogen) which are oxidised for energy release
187
What are fuel stores required for
Maintenance of a supply of glucose between meals
Providing intermediate fuel for increased activity
For long periods when food intake may be inadequate
188
Source of food stores in a normal 70kg person
Mainly TAGs in adipose (15kg, 590,000kJ of energy)
Protein in mainly muscle (6kg, 100,000kJ)
Glycogen in muscle and liver (223g, 3800kJ)- not much but can be obtained quickly
189
Features of triacylglycerol side chains
Can be a mixture of lengths or all the same
| Double bonds in side chains mean kinks in the phospholipid- in membranes this keeps fluidity
190
How are TAGs synthesised
Fatty acids from chylomicrons
Glycerol backbone from glucose
Activation of fatty acids to acyl-CoA
Esterification of acyl groups to glycerol-3-phosphate
All stimulated by insulin- tells the body it is fed
191
How is glycerol formed from glycolysis
DHAP-> glycerol-3-P by glycerol-3-phosphate dehydrogenase
| Glycerol-3-P-> glycerol-> triacylglycerol (via many steps)
192
How does mobilisation of triacylglycerols work
Hydrolysis of TAGs catalysed by hormone-sensitive lipase
Stimulated by hormones adrenaline and glucagon
Release of free fatty acids and glycerol
Hormones do this via G-protein coupled receptors-> second messenger-> protein kinases OR intracellular receptor proteins
193
Features of glycogen
Branched polysaccharide
a-1,4 and a-1,6 glycosidic bonds link glucose molecules
Stored in liver and muscle
Granules in cytoplasm
~60,000 glucose molecules per glycogen
If only glucose is stored= changes in osmotic pressure= cells burst
194
How does glycogen synthesis work
Occurs mainly in the liver and muscle immediately after a meal
Requires energy inputs (ATP and UTP)
Activated high-energy precursor UDP-glucose made
Glycogen synthase and branching enzyme
Stimulated by insulin
195
What does the glucose-> glucose-6-P-> glucose-1-P prevent
Glucose-6-P is used for glycolysis so this reaction diverts from glycolysis and ensures that doesnt happen when glucose is needed to be stored. Is reversible so can later undergo glycolysis
196
What are the linkages between a growing chain and between branches
```
Chain= a-1,4 glycosidic
Branches= a-1,6 glycosidic
```
197
What happens when there is excess glucose
Only so much space for glycogen so excess glucose is converted to acetyl-CoA and then into fatty acids by the FA synthase complex in the liver cytosol
198
How does mobilisation of glucose occur
Degraded by glycogenolysis
Liver glycogen is released as glucose in the blood-> brain
Muscle glycogen is released as fuel for glycolysis within muscle cells
199
Different fuels for certain tissues
```
Brain= glucose
RBCs= glucose
Liver= fatty acids
Heart= fatty acids
Muscle: at rest= fatty acids, when working= mis of fatty acids and glucose
```
200
How much triacylglycerol is stored in adipose tissue and what this means for energy during starvation
Atleast 15kg of fat in adipose
= 40 days of starvation for energy
Glucagon stimulates lipolysis
Fatty acids are used as fuel by all aerobic tissues except the brain
Get ~20g of glucose from TAG breakdown so extra glucose is needed
201
How much glucose does the brain use each day
~120g
202
Liver glycogen and starvation
~90-120g stored
Mobilised back into glucose
Stimulated by glucagon
Provides enough glucose for the brain for one day
203
What is the glycogen debranching enzyme
Glyocgen phosphorylase
204
Where and how does gluconeogenesis work
Occurs mainly in the liver and kidney cortex
Synthesis of glucose from lactate (muscle glycogen), alanine (muscle protein) and glycerol (TAGs in adipose)
Stimulated by glucagon
Fatty acid oxidation provides the energy required (acetyl CoA cant make glucose but gives needed ATP and ADH)
Brain uses most of the glucose
205
How much energy can we get from TAGs and how much glucose from glycerol per day during starvation
Burn 200g per day (at 40kJ/g)
200 x 40= 8000kJ per day
Glycerol= 20g of glucose per day
206
How much protein would be needed per day to give the rest of glucose needed during starvation and what would it mean
If using proteolysis for 100g would need ~150g of protein per day. Muscle reserves would therefore become critical in 2 weeks
207
Protein stores in the body and what it means for protein conservation
10-15kg in body, no specific storage proteins
Some protein is degraded to amino acids to make glucose
Loss of too much protein= structural and functional damage
This means protein needs to be conserved as much as possible
208
What did George F Cahill find with body fuel sources and starving for 40 days
Ketone amount increased 100x
Glucose was maintained
Free fatty acids increased 10x
209
Based on George F Cahill’s research what did harvad find
During a 6 week starvation of a diabetic it was found 50g of ketone bodies were used per day (50% of brains requirement during starvation)
Ketones are what diabetics produce in excess
210
During starvation, how much glucose does glucose and ketone bodies supply to the brain
20g + 50g= 70g
211
What are the body’s metabolic adaptations to starvation
Fatty acids can be used as a fuel by all aerobic tissues except the brain
There is essentially an unlimited supply from TAGs
Ketone bodies can be used by the brain
212
What does using ketone bodies by the brain mean for the body and surviving starvation
Brain needs less glucose per day (50g)
Muscle degradation can slow down- not so many amino acids needed for gluconeogenesis
The body can survive longer
213
How did starving man survive so long?
How did his brain continue to function?
What happened to his fat stores?
What happened to his muscles?
Fuel stores, gluconeogenesis, ketogenesis
Ketone bodies, glucose
Mobilised to fatty acids and glycerol
Proteolysis to amino acids
214
How much ATP is used and produced in one second
5 micro mol/g
215
What is anaerobic exercise and examples
High intensity
Rapid generation of force
Short periods
Eg sprinting and weight lifting
216
What is aerobic exercise and examples
Low intensity
Prolonged, sustained exercise
Eg long-distance running, swimming and walking
217
How anaerobic and aerobic exercise use muscle regeneration of ATP from ADP
Anaerobic- doesnt use O2, uses phosphocreatine and glycogen
| Aerobic- requires O2, uses oxidation of glucose and fatty acids
218
How does phosphocreatine make ATP for anaerobic exercise
```
On site, fast fuel
20 micro mol/g of muscle
High-energy phosphate compound
Phosphate transferred from ADP-> ATP
Made from gly and arg, the 20 micro mol/g lasts about 20 seconds
```
219
What did the experiment with increased creatinine show
With increased creatinine there was increased cycling work
220
How is glycogen used in anaerobic exercise
On site glucose store in muscle
Mobilised to glucose-1-P by glycogen phosphorylase
Glucose-1-P -> glucose-6-P as fuel for anaerobic glycolysis
221
What causes mobilisation of glycogen to provide a fuel for anaerobic glycolysis
Adrenaline binds to beta adenergic receptors on muscle cells and stimulates mobilisation. Continues as long as adrenaline hormone is bound to the receptor
222
How does anaerobic glycolysis work
Muscle glycogen as fuel, no need for O2
ATP is generated by substrate-level phosphorylation
Pyruvate is reduced to lactate to regenerate NAD+
ATP generation is rapid but for a short time (~20s of ATP)
Lactate (product) causes decrease in muscle pH which leads to fatigue
223
How is glycolysis regulated in exercising muscle
Glycogen mobilisation is stimulated by Ca2+ and adrenaline
| Phosphofructokinase activity is increased by allosteric regulators AMP and Pi
224
How does anaerobic glycolysis make the most of ADP
ADP+ADP-> ATP + AMP
225
How does aerobic exercise use glucose oxidation to maintain ATP
Blood supplies fuels- mainly rely on fatty acids
Blood supplies O2
Active citric acid cycle
ETC in oxidative phosphorylation
226
What type of muscle do aerobic and anaerobic athletes tend to have
Aerobic- mainly type I
| Anaerobic- mainly type II
227
How do aerobic athlete muscle adaptations work for endurance training and keeping up oxidative phosphorylation
Selective hypertrophy of type I fibres
Incr no of blood capillaries per muscle fibre
Incr myoglobin content
Incr size and no of mitochondria= incr cristae
Incr capacity of mitochondria to generate ATP by oxidative phosphorylation
Incr capacity to oxidise lipid and carbohydrate
228
Performance enhancing drug examples and what they do
EPO- incr RBC count= more O2
Anabolic steroids= more muscle
Growth factors= more muscle, recombinant IGF-1, GH
229
How can gene therapy be used for exercise/ muscle performance increase
Turn off myostatin gene (like those buff cows have)
| Regulation of transcription factors- upregulate of PGC-1 or turn off PPAR
230
Symptoms of type I diabetes
```
Fatigue
Weight loss
Intense thirst
Frequent urination
Hyperglycemia
Glucosuria
Ketones
```
231
Features of type I diabetes
```
Insulin dependent
Auto-immune destruction of B cells
Onset age 1-25yr
Cause= genetic and enviro factors (viruses or toxins)
Insulin injections
```
232
Features of type II diabetes
```
Non-insulin dependent, maturing onset
Resistance to insulin action
Onset age >40yr
Cause= genetic and enviro factors (obesity, sedentary lifestyle)
Diet, exercise and drugs help
```
233
What happens if blood glucose goes too low
Signal to eat- might get shakes
If very low <1mmol/L= sweating, incr heart rate, SNS causes vomiting
Cognitive impairment, no glucose to provide energy for the brain= aggressive moods, convulsions and coma
234
What happens if blood glucose goes too high
Non-enzymatic glycation of protein- Lys residues
Can target crucial structural proteins
Eg- collagen in basement membrane of capillaries and crystalline protein of eye making lens go opaque
Constriction of blood vessels= gangrene and limb amputations
235
Long term effects of high glucose levels
```
Cardiovascular disease
Peripheral vascular disease
Neuropathy
Nephropathy
Retiropathy
```
236
Features of insulin
Peptide hormone
Synthesised by pancreatic B cells
Secreted as a result of high blood glucose after a meal
Acts on liver, muscle and adipose tissue
237
What are the two overall actions of glucose
Increase anabolic uptake and storage of fuels
| Anti-catabolism
238
What are insulin anabolic actions
Glucose uptake in muscle and adipose
Protein synthesis
Glycogen synthesis
TAG uptake, fatty acid synthesis
239
What are insulin anti-catabolic actions
```
Gluconeogenesis
Ketogenesis
Lipolysis
Proteolysis
Glycogenolysis
```
240
How does a glucose tolerance test work
Fast overnight, take 75g of glucose and measure the time it takes for it to be cleared from the blood (normally 1-1.5 hours)
241
Metabolic consequences of a lack of insulin
```
Impaired glucose uptake and storage by muscle
Increased mobilisation of glucose
Increased glucose synthesis
Increased lipolysis
Increased ketone body synthesis
Reduced removal of TAG from blood
Increased breakdown of tissue protein
Starts to mimic starvation as there of no ‘fed’ signal from insulin being absent
```
242
Why do people with diabetes breaths smell like ketones
Because keto acids acetone are made more in the body
243
Treatments of type I diabetes
Injections of recombinant human insulin from cows and pigs (only used these animals since 1980s). Acts to mimic the normal rise in insulin caused by meals
Too much= hypoglycemia and coma if ,1mmol/L
244
Treatments of type II diabetes
Aim to increase sensitivity of tissues to insulin by: weight loss, increased exercise or hypoglycemia drugs
Hypoglycemia drugs include: sulphonylureas, glitazones and insulin injection if necessary
245
Obesity in New Zealand, facts and issue?
~28% of NZ-ers are obese (1.12mil) with <600 bariatric surgery spaces available
Issue that is getting worse
Greater risk of type II diabetes, coronary heart disease, cholelithiasis and hypertension
246
How is BMI calculated and what are the different ranges and their meanings
```
BMI= w/h^2 weight in kg and height in m
>30= obese
25-30= overweight
20-25= healthy weight
<20= underweight
```
247
How is energy used/ energy expenditure breakdown in the body
50% BMR
30% physical activity/ exercise- varies between people
20% adaptive thermogenesis- variable and regulated by the brain, responds to temp and diet, occurs in brown adipocyte mitochondria, skeletal muscle and other sites
248
Features of 2,4-dinitrophenol
First identified in a bomb factory in WWII
1950s was used as a weight control method
Caused death from neurological disorders
Uncoupler- moves across IMM lipid bilayer and makes H+ equal on both sides, no pmf. Heat is therefore produced to try and make the pmf again by the ETC
249
Features of brown fat
Special thermodynamic tissue
In hibernating animals, babies around vital organs, low in adult humans (some around shoulders)
Keeps hibernating animals and babies warm
Many uncoupled mitochondria and fat droplets with abundant cristae
250
Features of uncoupling proteins (UCP)
Originally found in brown fat
Present in IMM
Regulated proton channels in membrane (holes)
Uncouple ATP synthesis from fatty acid oxidation
Electrochemical potential gradient gone= heat release leading to increased metabolic rate and burning of excess fat
251
H+ channel regulation by uncoupling proteins and what controls the proteins
H+ channel open in cold causing warming and closed in warm preventing excess heat
SNS- noradrenaline regulated
252
Penguin metabolic adaptations
Avian uncoupling protein (avUCP)
Highly expressed in mitochondria of pectoral muscles
Oxidise fatty acids= heat
253
Diet-induced thermogenesis in rodents and humans (example from lecture)
Rodents- cafeteria diet- activated UCP in brown adipose tissue burns excess dietary energy
Humans- research shows active BAT could burn off excess energy from related uncoupling proteins UCP2 and UPC3 in white adipose tissue in muscle. Can raise metabolic rate and release heat to burn excess energy and prevent obesity
254
BAT-oriented strategies for obesity
Stimulate existing BAT
Switch to brown fat differentiation and growth
Transplantation of engineered BAT
255
How does brown fat differentiation work and two ways it can be done
Controlled by expression of specific transcription factors. At specific times in specific tissues= differentiation of cells into BAT cells
Vivo approach- active BAT-mediated through thermogenesis, promote muscle thermogenic function and increase general mitochondrial uncoupling
Ex vivo approach- cell based therapy- isolate progenitors (liposuction), induce in vitro promoting BAT differentiation, transplant back into donor to generate functional BAT= no immune response as it is their own cells
256
Obesity genetic component (leptin and the receptor)
Obese gene- codes for leptin 16 kDa protein. Mutant obese ob/ob doesnt produce leptin
Leptin- hormone secreted from ‘fat’ fat cells and signals brain to; stop food uptake, increase energy expenditure therefore, maintaining normal animal ‘in’ energy balance
Leptin receptor is present in hypothalamus and other brain areas. It is absent in obese diabetic mouse db/db and fatty rat fa/fa
257
Leptin in humans and obesity
Secrete from adipose
Receptor in brain
Some obese have a mutation in leptin or leptin receptor= constantly wanting to eat and not bale to have the will to stop or want to use energy= massive weight increase at a young age
Most obese humans are resistant to a leptin receptor= rare
258
Obesity development influencers
Genes- monogenic syndromes and susceptibility genes
| Environment- exercise, food intake and culture
259
Molecular targets and corresponding drugs
```
Food breakdown (pancreatic lipase blocked= less fat absorbed) by drug xenical
Satiety signals (increased leptin levels or gut satiety factors) with clinical trials underway
Mitochondria and brown fat (uncouple oxidative phosphorylation from ETC by upregulate uncoupling proteins with drugs or increased BAT) possibly for the future
```
