Metabolism Flashcards
0
Q
What components make up your daily energy expenditure?
A
Basic metabolic rate
Voluntary physical activity
Diet induced thermogenesis
1
Q
Define energy?
A
The capacity to do work: osmotic, biosynthesis, electrical, transport, mechanical,
2
Q
Define basic metabolic rate
A
Basal energy required to maintain life function of various tissues & organs in the body
3
Q
What effects you basic metabolic rate?
A
Gender, body weight, body temperature, thyroid status, if pregnant or lactation
4
Q
What effects your voluntary physical activity?
A
Intensity and duration of activity
5
Q
Define diet induced thermogenesis
A
Is the energy used to process the food we eat (digest, absorb, distribution)
6
Q
What are the essential components of the diet?
A
Macronutrients: carbohydrates, fats, proteins
Micronutrients: minerals, vitamins
Water
Fibre
7
Q
Name the 8 essential amino acids?
A
Lysine, isoleucine, leucine, threonine, valine, tryptophan, Phenylalanine, methionine,
8
Q
Name the minerals required by the body?
A
Na, K, Ca, Mg, P, S, Cl
9
Q
Name the vitamins needed by the body
A
K, A, D, E, C, B groups
Are antioxidants, fat and water soluble
10
Q
Define homeostasis
A
Control of the internal environment within set limits, is a dynamic equilibrium and not a steady state
11
Q
Define obesity
A
Clinical condition characterised by body fat, having a BMI>=30
12
Q
What are the conditions/diseases associated with obesity?
A
Type ll diabetes, hypertension, stroke, various cancers, gall bladder disease, osteo artheritus
13
Q
What are the signs and symptoms of protein deficiency?
A
Impaired physical and mental development, oedema, increased risk of infection (due to reduced immunoglobin synthesis), anaemia (reduced haem synthesis), fatty liver (reduced lipoprotein synthesis)
14
Q
In marasmus…. (Cal intake, protein intake, oedema, appearance)
A
Cal intake: inadequate Protein intake: inadequate Oedema: absent Appearance: thin bony child, fat stores mobilised, ketones and Gluconeogenesis, glycogenolysis, pituitary hormones effected
15
Q
In kwashiorkor…..(cal intake, protein intake, oedema, appearance)
A
Cal intake: poor to normal Protein intake: inadequate Oedema: present Appearance: thin child with a pot belly Hepatic dysfunction, fatty liver, unable to synthesise necessary enzymes & proteins, damage from accumulating toxins
16
Q
Define cell metabolism
A
The set of processes which derive ready and raw material from food stuffs and are there to support repair, growth and activity of tissues of the body to maintain life
17
Q
Functions of cell metabolism?
A
- energy needed for cell function & synthesis of cell components
- building block molecules that are used in the synthesis of cell components needed for growth, maintenance, repair & division of cells
- organic precursor molecules that are used to allow the inter conversion of building block material e.g. Acetyl~CoA
- bio synthetic reducing power used in the synthesis of cell components (NADPH)
18
Q
What are the origins of nutrients?
A
The diet, synthesis in the body tissues from pre cursors, released from storage in body tissues
19
Q
What are the fates of nutrients?
A
Degradation to release energy (all tissues), synthesis of cell components (all tissues except erythrocytes), storage (liver, adipose tissues, skeletal muscle), inter conversion to other nutrients (liver, adipose tissue, kidney cortex), excretion (liver, kidney, lungs)
20
Q
Define catabolism and what are its properties?
A
Break down of larger molecules into smaller ones
- degrative
- oxidative
- +ve entropy change
- releases large amounts of free energy -ve G
- produces intermediary metabolites
21
Q
Define anabolism and what are its properties?
A
Smaller molecules are build up into larger ones
- biosynthetic
- reductive
- small +veG
- uses ther intermediatary metabolites and ATP/energy produced by catabolism to drive the synthesis of important cell components
22
Q
Why do cell need a continuous supply of energy?
A
All cells need energy to perform there function and they need a continuous supply of energy
- perform specialised functions (mechanical, osmotic, electrical)
- transport work (membranes, maintenance of concentration gradients)
- biosynthetic work (synthesis of cellular components)
23
Q
Exergonic reactions have a what G?
A
Change G < 0
24
Endergonic reactions have a G what?
Change in G > 0
| Units: KJ mol^-1
25
What is a high energy of hydrolysis bond?
It is a bond that links a terminal phosphate group to the rest of a molecule. The energy is in a covalent bond as chemical bond energy and this energy is released when the bond is hydrolysed
26
What is Creatine phosphate?
Small store of Earney in skeletal and cardiac muscle that is generated in ATP concentration it high
27
How is Creatine phosphate formed?
Creatine + ATP Creatine phosphate + ADP
28
What is the role of high energy signals? And give examples?
Indicate cell has adequate energy levels for its immediate needs
Activates anabolic pathways
E.g. ATP, NADH, NADPH, FAD2H
29
What is the role of low energy signals? Giving examples
Indicates that the cell does not have adequate energy levels for its immediate needs
Activates catabolic pathways
E.g. AMP, ADP, NAD+, FAD NADP+
30
What is the general formula of carbohydrates?
(CH2O)n
31
What are the monosaccharide sugars?
Glucose, fructose, galactose
32
Monosaccharides have?
3-9 carbon atoms, contain an asymmetric carbon atom, have stereoisomers with D (natural) and L forms which enzymes can distinguish, exist as ring structure where aldehyde or keto group has reacted with an alcohol group
Glucose has an alpha or beta form
33
What is a disaccharide? Give examples?
Is the product of the condensation reaction of two monosaccharides forming a glycosidic bond (alpha or beta) with the elimination of water
E.g. sucrose, lactose, maltose
34
What makes a disaccharide non reducing?
Is the aldehyde or keto group is involved in forming glycosidic bonds
35
What's are the monosaccharides that make up sucrose?
Glucose and fructose
36
What's are the monosaccharides that make up lactose?
Galactose and glucose
37
What's are the monosaccharides that make up maltose?
Glucose and glucose
38
How are polysaccharides produced?
They are polymers of monosaccharides units linked by glycosidic bonds.
Most are homopolymers: made by polymerisation of 1 monosaccharide
39
What are the three types of polysaccharides?
Glycogen, starch, cellulose
40
Why can't the body digest cellulose but it can digest starch and glycogen?
This is because cellulose despite being a structural polymer of glucose has B1-4 linkages and humans do not have the enzymes to break these. Where as glycogen (animals) and starch (plants) which are also polymers of glucose have alpha 1-4 and alpha 1-6 glycosidic bonds which humans do have the enzymes to break (amylase, amylopectin for starch)
41
Describe how dies try carbohydrates are digested and absorbed?
(Mouth, deudenum, jejunum)
Mouth: dietary polysaccharide hydrolysed by salivary amylase
In the duodenum: pancreatic amylase continues this and dietary disaccharides, maltose, detrix are digested by glycosidase enzymes which are aprt of glycoprotein complexes attached to epithelial cells
In the jejunum: lactase, glycoamylase, sucrose, isomaltase
The absorbed by:
Active transport into cells linin the gut then transported form these cells into the blood and from the blood into tissues via facilitated diffusion using glut 1 - 5 transport proteins which have different distribution reflecting the different tissues requirements for glucose
42
What tissues have glucose requirement?
RBC, WBC, kidney medulla, lens of eye, CNS
43
What are the key features of glycolysis?
- starting material, end products, intermediates are C6 or C3
- no loss of CO2
- some C3 intermediates are useful for cell function
- exergonic process
- all intermediates are phosphorylated
- net moles of 2 ATP: 2 utilised and 4 produced
44
What are the three regulatory steps in glycolysis?
1. Hexokinase/glucokinase - glucose to glucose-6P allosteric
3. Phosphofructokinase - fructose-6-phosphate to fructose-1,6-bisphosphate allosteric
10. Pyruvate kinase - phosphophenylpyruvate to pyruvate covalent modification
All regulated by high/low energy signals + hormones (insulin& glucagon)
45
What is the advantage to lactate production?
Allows glycolysis to continue as it increases NAD+ concentration so small amounts of ATP are still generated
46
Where is lactate converted to CO2?
Heart and muscle
| Converted back to pyruvate and oxidised to CO2
47
Where is lactate converted to glucose?
In the liver
48
What effects the blood concentration of lactate?
Utilisation (liver, heart) thymine deficiency + congestive heart alcohol metabolism reduce this
Production (exercise, hearty eating, congestive heart disease)
Disposal (kidney)
49
What is the normal concentration of lactate in the blood? For hyperlacteaemia? For lactic acidosis?
5mmol/L above renal threshold therefore blood pH is lowered
50
Describe the pentose phosphate pathway
Glucose-6-phosphate to 5C sugar phosphate using NADP->NADPH + CO2
Then to fructose-6-phosphate or glyceraldehyde-3-phosphate
51
What is the role of pyruvate dehydrogenase?
Responsible for the conversion of pyruvate to acetyl~CoA
- mitochondrial matrix
- irreversible
PDH: large multi sub unit enzyme inhibited by high energy signals (allosterically) activated by low energy signals (allosteric) insulin by covalent modification by dephosphorylation
52
How is the TCA cycle regulated?
ATP/ADP ratio
NADH/NAD+ ratio
Allosteric regulation of is isocitrate dehydrogenase inhibited by NADH and activated by ADP
53
What are the three ways in which the electron transport chain and ATP synthesis can be uncoupled?
1. Uncouplers, increase the permeability of inner mitochondrial membrane to protons e.g. Dinitrophenol
2. Inhibition of electron transport e.g. Cyanid, CO, anaerobic conditions
3. Ox/Pho disease, genetic defects in proteins coded for by the mitochondrial DNA
4. Uncoupling proteins, UCP 1-5, brown adipose tissue
54
What is the anabolic function of the TCA cycle?
```
Can produce amino acids from:
Alpha-ketoglutarate, succinate, oxaloacetate, fumerate
Can produce fatty acids from:
Citrate, acetyl CoA
Can synthesise haem from:
Succinate
Can produce glucose from:
Oxaloacetate
```
55
What are the three classes of lipids?
1. Fatty acid derivatives: FA, TAG, phospholipids, eicosanoids
2. Hydroxy-methyl-glutaric acid derivatives: ketone bodies, cholesterol, cholesterol esters, bile acids & salts
3. Vitamins: KADE
56
Why does acetyl-CoA have a central role in metabolism?
Main convergence point for catabolic pathways:
aa, FA, sugars, alcohol
Important in anabolic pathways
Important intermediate in lipid biosynthesis
57
Where does the catabolism of fatty acids take place?
Liver, heart muscle, skeletal muscle (not RBC, no mitochondria or brain, can't pass through blood brain barrier)
58
Describe fatty acid metabolism
1. ACTIVATION: FA linked to coenzyme A (compex molecule containing pantheonic acid with free -SH groups) via the S-atom forming a high energy of hydrolysis bond. Requires ATP
2. Transport into Mitochondria using a carnitine shuttle transporter:
fatty acyl~CoA + carnitine ----> Acyl carnitine + CoA (CAT 2)
Acyl carnitine + CoA ----> carnitine + Fatty acyl~CoA (CAT 1)
3. Beta Oxidation:
Cycle of reactions, 2C removed per cycle, H+ and e- transferred to NAD+ and FAD, stops in absence of oxygen, no ATP synthesis, all intermediates in pathway are linked to CoA, C atoms of fatty acids are converted to acetyl CoA
59
Describe the synthesis of Ketone Bodies
Acetyl~CoA ----> HMG-CoA (synthase)
HMG-CoA ----> acetoacetate (lyase)
Acetoacetate ----> acetone (volatile can smell on breath)
Acetoacetate ----> B-Hydroxybuterate
60
Describe the synthesis of cholesterol
Acetyl~CoA ---> HMG-CoA (synthase)
HMG-CoA ---> Mevalonate (HMG-CoA reductase)
Mevalonate ---> cholesterol
61
How is the synthesis of ketone bodies and cholesterol controlled?
1. Glucagon --> ketone bodies, starvation
2. Insulin ---> cholesterol, well fed
Lyase and reductase enzymes are reciprocally controlled by insulin and glucagon
62
What are the three ketone bodies?
Acetoacetate
Beta-hydroxybuterate
Acetone
63
Describe glycogen synthesis
1. Glucose to glucose-6-phosphate using ATP -> ADP
Hexokinase/glucokinase
2. Glucose-6-phosphate to glucose-1-phosphate
Phosphoglucmutase
3. Glucose-1-phosphate + UTP + H2O to UDP glucose + 2Pi
4. Glycogen (n residues) + UDP glucose to glycogen (n+1 residues) + UDP
Glycogen synthase
Branching enzyme
64
Describe glycogen metabolism
Glycogenolysis:
1. Glycogen (n residues) + Pi to glucose-1-phosphate + glycogen (n-1 residues)
Glycogen phosphatase, de branching enzyme
2. Glucose-1-phosphate to glucose-6-phosphate
3. Glycolysis or glucose-6-phosphate + H2O to glucose + Pi
Glucose-6-phosphatase
65
Why are glycogenolysis and glycogenesis not the reverse of each other?
Allows greater metabolic flexibility and independent control
66
How are glycogenolysis and glycogenesis regulated?
Glycogen phosphatase and glycogen synthetase:
Allosteric regulation by AMP
Covalent modification by glucagon and insulin:
Glucagon: phosphorylation inhibited synthetase and activating phosphatase reverse for insulin
67
What is Gluconeogenesis? And how does it occur?
Production of new glucose from a number of precursors: galactose, fructose, glycerol, lactate, glucogenic aa, pyruvate
68
What is the role of the pentode phosphate pathway?
To produce NADPH in the cytoplasm:
- > Provide reducing power for anabolic processes
- > In RBC maintains free -SH/thiol groups on cysteine residues
- > is used in detoxification reactions, protects cell from toxic chemicals
Produces C5 ribosome for the synthesis of nucleotide so has a high activity in dividing tissues
69
What the enzyme missing in fructosuria?
Fructokinase
| So Fructose is present in the urine but there is no clinical signs
70
What is the enzyme missing in fructose intolerance?
Aldolase?
71
Which is more serious fructosuria or fructose intolerance?
Fructose intolerance as fructose-1-phosphate accumulates in the liver which results in damage. In Fructosuria there are no clinical signs but fructose is present in the urine.
72
What are the three enzymes that regulate glycolysis?
Hexokinase/glucokinase (liver)
Phosphofructokinase
Pyruvate kinase
73
Which out of the Hexokinase, phosphofructokinase and pyruvate kinase is regulated by covalent modification in glycolysis?
Pyruvate kinase: dephosphorylation high insulin:glucagon
74
What reaction does Hexokinase catalyse?
Glucose -> glucose-6-phosphate
| ATP--> ADP
75
Where does glycolysis occur?
In the cytoplasm
76
What reaction does phosphofructokinase catalyse?
Fructose-6-phosphate -> fructose-1,6-bisphosphate
| ATP --> ADP
77
What reaction in glycolysis does pyruvate kinase catalyse?
Phosphoenol pyruvate -> Pyruvate
| ADP-->ATP
78
Name two important intermediate in glycolysis and explain why they are important?
Dihydroxyacetone:
Goes to glycerol phosphate with NADPH-> NAD+
Important in triacylglycerol and phospholipid synthesis
Liver & adipose tissue
1,3-bisphosphoglycerate:
In RBC goes to 2,3-BPG, which lowers the affinity of haemoglobin for oxygen,
79
How many specialised protein complexes are there in the electron transport chain? Out of those how many are proton transferring complexes?
4 and 3 are
80
What is the name given to oxygen in the electron transport chain?
Acts as terminal electron acceptor
81
What is the result of the electron transport chain?
As the inner membrane of the mitochondria is impermeable to protons the chemical bind energy of the electron is transferred into an electrochemical potential difference of protons -> a proton motive force.
82
How do protons re enter the matrix from the intermembrane space in a mitochondria?
Via ATP synthetase
83
How many moles of ATP does 2 moles of NADH produce?
5
84
How many moles of ATP does 3 moles of FAD2H produce?
3 moles
85
Why is the electron transport chain and ATP synthesis tightly linked?
Because one does not occur without the other:
If the ADP concentration is low then ATP synthetase transport of protons back into the matrix due stops due to lack of substrate. This prevents protons being transported back into the matrix. As a result the proton concentration increase preventing more protons being pumped into the inter mitochondrial membrane space. Absence of proton pumping means the electron transport chain stops.
86
Name 4 ways in which the uncoupling of the electron transport chain and ATP synthesis can occur?
1. Uncouplers e.g. Dinitrophenol which increase permeability of inner mitochondrial membrane to protons
2. Inhibits of electron transport chain e.g. Cyanide, CO, anaerobic conditions. Blocks flow of electrons
3. Ox/pho disease, genetic defects in proteins coded for by the mitochondrial DNA
4. Uncoupling proteins, proteins whose function is to uncouple ET and ATP production to produce heat. E.g. UCP1
Found in brown adipose tissue
87
Where does the TCA cycle and the reaction catalysed by pyruvate dehydrogenase take place?
In the mitochondrial matrix
88
Describe the differences between oxidative phosphorylation and substrate level phosphorylation
Oxidative phosphorylation:
- requires membrane associated complexes
- energy coupling occurs indirectly through generation and subsequent usage of PMF
- cannot occur in the absence of oxygen
- major process for ATP synthesis in cells that require large amounts of energy
Substrate Level Phosphorylation:
- requires soluble enzymes
- energy couple occurs directly through the fora iron of a high energy of hydrolysis bond
- can occur to a limited extent in the absence of oxygen
- minor process for ATP synthesis in cells that require large amounts of energy
89
What is the enzyme that catalyses glucose-6-phosphate to C5 sugar phosphates?
Glucose-6-phosphate dehydrogenase
NAD+ --> NADPH
CO2 and H+ produced
90
What is the pentose phosphate Pathway controlled by?
NAD+/NADPH ratio
91
Describe the catabolism of fatty acids?
1. Activation:
FA linked to coenzyme a forming fatty acyl CoA by fatty acyl CoA synthase
2. Transport into mitochondria:
Fatty acyl CoA + carnitine converted to acyl carnitine and CoA by CAT2
Then reverse using CAT1
Called carnitine shuttle transporters
3. Beta oxidation
A cycle of oxidation reaction where 2c removed per cycle to produce NADPH and FAD2H. Will stop in absence of oxygen
92
Where does catabolism of fatty acids occur?
Liver, heart muscle, skeletal muscle.
Not RBC or brain
93
What does Malonyl CoA inhibit?
Is an intermediate in FA synthesis and prevents newly synthesised FA being transported into the mitochondria by the carnitine shuttle transporter
94
Name the two main ways in which lipids are transported in the blood?
1. Bound non covalently to albumin = 2%
| 2. Lipoprotein particles = 98%
