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MEH session 1 Flashcards

1
Q

What is metabolism?

A

Metabolism is the set of processes which derive energy and raw materials from food stuffs and use them to support repair, growth and activity of the tissues of the body to sustain life.

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2
Q

How are waste products lost from the blood?

A

Via the kidneys/lungs

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3
Q

Are catabolic pathways oxidative or reductive?

A

Oxidative

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4
Q

Are anabolic pathways oxidative or reductive?

A

Reductive

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5
Q

What is catabolism?

A

Catabolism describes the metabolic pathways in which the overall reaction is the breakdown of larger molecules into smaller ones.

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6
Q

What is the relationship between anabolism and catabolism?

A

Energy (ATP) released in catabolism (breaking down of large molecules into smaller intermediary metabolites) is used in anabolism (synthesis of large important cellular components from intermediary metabolites).

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7
Q

What are the roles of the products of catabolic metabolism? (4)

A
  1. Building block materials (sugars, amino acids, fatty acids)
    – dynamic state of cell components (turnover)
    – cell growth and division – repair
  2. Organic precursors (Acetyl CoA)
    – allow for inter-conversion of building block material
  3. Biosynthetic reducing power (NADH, NADPH)
  4. Energy for cell function (Adenosine triphosphate, ATP)
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8
Q

Why do cells need a continuous supply of energy? (3)

A 
1. Biosynthetic work - anabolism
Synthesis of cellular components
2. Transport work - membranes
Maintenance of ionic gradients
Nutrient uptake
3. Specialised functions
Mechanical work-muscle contraction 
Electrical work-impulse conduction
Osmotic work-kidneys
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9
Q

What are the components of your daily energy expenditure?

A

Basal metabolic rate
Voluntary physical activity - muscular work
Diet induced thermogenesis - ingestion, digestion, absorption

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10
Q

What happens when energy intake exceeds energy required?

A

Excess energy is stored:
Growth - synthesis of new tissue
Production of adipose tissue

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11
Q

What happens if energy requirements exceed energy intake?

A

Tissue is lost

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12
Q

What is the difference between exergonic and endergonic reactions?

A

Exergonic reactions release energy, reaction is spontaneous. Reactants are at a higher energy level than products.
Delta G < 0
Endergonic reactions require energy, reaction is not spontaneous. Reactions are at a lower energy level than products.
Delta G > 0

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13
Q

What prevents spontaneous reactions from continuously occurring in the cell?

A

Activation energy is required to from the transition state. Enzymes facilitate the formation of this highly reactive transition state.

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14
Q

What is the reducing power of carriers used for?

A 
ATP production (NADH + H+)
Biosynthesis (NADPH)
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15
Q

What proof is there to show that there is a constant cycle between oxidative and reductive processes?

A

Concentration of oxidised and reduced carriers is constant.

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16
Q

What in our diet contains H-carrier molecules?

A

Vitamin B

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17
Q

How many hydrogen atoms are required to reduce a H-carrier?

A

H- carriers are converted to their reduced form by adding two hydrogen atoms. One hydrogen atom joins to the carrier by a covalent bond and one is dissociated in solution.

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18
Q

Why is ADP only a carrier and not a store?

A

Limited concentration of ADP. Only enough for a few seconds.

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19
Q

How does ATP allow the flow of energy to be controlled?

A

It is stable in the absence of specific catalysts

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20
Q

What is our ATP turnover?

A

Turnover body weight in ATP each day

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21
Q

How do low and high energy signals affect our cells?

A

High ATP, NADH, NADPH, FAD2H concentrations activate anabolic pathways
Low ATP concentration, high ADP, AMP, NAD+, NADP+, FAD concentrations, activate catabolic pathways

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22
Q

What reaction is catalysed by creatine kinase? Where does this occur?

A

Creatine + ATP —> phosphocreatine + ADP
Can go on opposite direction
In cells that need to increase metabolic activity very quickly eg. Muscle

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23
Q

Creatine kinase concentration in the blood elevated in all types of damaged muscle. How can we differentiate whether skeletal muscle or cardiac muscle has been damaged when using creatine kinase as a marker for a myocardial infarction?

A

Creatine kinase is made up of two subunits. One subunit is coded for by M gene and the other by B gene
Different isoform combinations are found in different tissues.
One isoform combination is specific to heart muscle so ensure that isoform combination is compatible with the heart
Appears in blood after a few hours

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24
Q

What is creatinine and how is it formed?

A

Normal spontaneous breakdown of phosphocreatine and creatine produces this waste product at a constant rate (unless muscle is wasting) which is excreted via the kidneys in the urine.

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25
Q

What is creatinine excretion proportional to? What can creatinine be used as a marker for?

A

The muscle mass of an individual
Creatinine concentration in urine is a marker of urine dilution (can be used as a standard) so can be used to estimate true urinary loss of many substances

The kidney is normally very efficient at removing creatinine from the blood. Thus, an abnormally high blood creatinine with low urinary creatinine concentration may indicate reduced kidney function.

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26
Q

How can reducing power be converted to energy currency (ATP)?

A

Oxidative phosphorylation

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27
Q

What chemical processes occur within a living organism in order to maintain life?

A

Oxidative pathways- catabolism
Biosynthetic pathways- anabolism
Detoxification pathways eg. Cytochrome P450 pathways
Fuel storage and mobilisation pathways eg. Store of glycogen in liver and muscles, store of fat in adipose tissue

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28
Q

What are the different ways in which energy is stored in the body?

A

Glycogen in muscle and liver cells

Fat in adipose tissue

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29
Q

How can we produce ATP?

A 
Oxidation of:
Lipids
Carbohydrates 
Protein (last resort)
Alcohol
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30
Q

What are the waste products of breaking down fuel stores?

A

Carbon dioxide, water, heat

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31
Q

Convert 1 kCal to kilojoules.

A

4.2 kilojoules

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32
Q

What is the general structure of a carbohydrate?

A 
General formula  (CH2O)n 
Contains an aldehyde (-C=OH) or ketone (-C=O) group 
Multiple –OH groups
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33
Q

What monosaccharides are sucrose and lactose and maltose made up from?

A 
Sucrose = glucose and fructose
Lactose = galactose and glucose 
Maltose = glucose and glucose
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34
Q

Which amino acids are the ‘essential’ amino acids? Why are they known as this?

A 
Our body cannot synthesise these amino acids so they must be acquired in the diet. 
Isoleucine-- If 
Leucine-- Learned
Threonine-- This
Histidine-- Huge
Lysine-- List
Methionine-- May
Phenylalanine-- Prove 
Tryptophan-- Truely
Valine-- Valuable
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35
Q

Why is protein of animal origin considered high quality and proteins of plant origin considered lower quality?

A

Proteins of animal origin contain all essential amino acids and proteins of plant origin are mostly deficient in one or more essential amino acids

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36
Q

What is a lipid composed of?

A

Triacylglycerols - 3 fatty acids esterified to one glycerol.

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37
Q

Why is more energy yielded when fats are oxidised?

A

Fats contain much less oxygen than carbohydrates or protein (they have greater reducing power)

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38
Q

Which vitamins are fat soluble and what does inadequate intake of these cause?

A

A - xerophthalmia (abnormal dryness of conjunctiva of the eye)
D- rickets
E - neurological abnormalities
K- defective blood clotting

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39
Q

What are the essential fatty acids?

A

Linoleum, linolenic acids

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40
Q

What is cod liver oil a good source of?

A

Essential fatty acids linoleic and linolenic acids

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41
Q

What are the essential components of the diet and why are they essential?

A

Carbohydrate – provides energy needed for cell function.
Protein - needed to supply essential amino acids.
Vitamins & Minerals - needed to prevent signs and symptoms of deficiency states.
Lipid - needed to supply essential fatty acids, reduces bulk of diet.
Water - needed to replace water lost in sweat, urine, faeces and breath.
Unrefined carbohydrate (Fibre) - required for normal GI tract function.

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42
Q

Define the components of daily energy expenditure.

A

Daily energy expenditure is the sum of:
Basal metabolic rate (BMR)
Diet induced thermogenesis (DIT) - energy required to process food
Physical activity level (PAL)

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43
Q

What factors does the extent of variation in energy requirements between individuals depend on?

A

Age
Sex
Body composition
Physical activity

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44
Q

What does the basal metabolic rate control?

A

Maintains resting activities of the body

Maintenance of cells

  • ion transport across membranes
  • biochemical reactions

Function of organs

  • skeletal muscle 30%
  • liver 20%
  • brain 20%
  • heart 10%
  • other 20%

Maintaining body temperature

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45
Q

What factors affect basal metabolic rate?

A

Body size, SA
Gender, males higher than females
Environmental temp, increases in cold
Endocrine status, increased in hyperthyroidism
Body temperature, 12% increase per degree

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46
Q

Describe factors involved in the regulation of body weight.

A

Stable body weight
Energy intake = energy expenditure

Energy stores (fat) increase
Energy intake > energy expenditure

Energy stores deplete
Energy intake < energy expenditure

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47
Q

What is the BMI used for?

What is the equation to calculate BMI?

A

To clinically evaluate patient weight

BMI = weight (kg)/ height squared (metres squared)

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48
Q

What are the benefits and limitations of the BMI?

A

Shows good correlation with body fat measurements

However, very muscular individuals may be wrongly classified as obese

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49
Q

How do we interpret BMI?

A

For both males and females:

<18.5 underweight
18.5-24.9 desirable weight
25-29.9 overweight 
30-34.9 obese
>35 severely obese
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50
Q

How is distribution of body fat clinically important?

A 
Individuals with a greater proportion of fat in upper body, especially their abdomen compared with that on the hips have more fat around visceral organs. 
This is associated with increased risk of:
Insulin resistance
Hyperinsulinism 
Type 2 diabetes
Hypertension 
Hyperlipidaemia 
Stroke 
Premature death
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51
Q

What are the clinical consequences of malnutrition?

A

Damage to tissues due to low energy intake
Low protein intake can result in insufficient protein synthesis (less albumin produced by liver) leading to a decrease in plasma oncotic pressure and oedema.

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52
Q

How can low protein intake cause oedema?

A

Low protein in diet
Less plasma proteins produced, particularly albumin which is produced by the liver
Lower oncotic pressure of blood
Less water returns from interstitial fluid at venous end of capillary
Oedema

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53
Q

What is the normal fasting plasma concentration of glucose?

A

3.3-6.0 mmol/L

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54
Q

What are the clinical consequences of energy deficiency?

A

Long term stores in adipose used

Under extreme conditions, muscle proteins can be converted to energy

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55
Q 
Order the following in terms of highest to lowest energy content (kJ/g):
Protein
Alcohol
Fat
Carbohydrates
A

Fat 37 kJ/g
Alcohol 29 kJ/g
Protein, carbohydrate 17 kJ/g

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56
Q

How would a high fibre diet reduce the risk of cholesterol and risk of diabetes?

A

Cholesterol is used to produce bile salts that are released into the GI tract
Fibre sequesters the bile salts so that they are passed out into the faeces along with the fibre
More cholesterol is then taken from the blood into the GI tract to produce more bile salts

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57
Q

What does a low fibre diet cause?

A

Constipation
Bowel cancer
High cholesterol

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58
Q

What does fibre consist of?

A

Cellulose
Lignin
Pectins
Gums

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59
Q

Why can’t we digest cellulose?

A

We do not produce the required enzymes to break the beta 1, 4 glycosidic bonds in cellulose

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60
Q

What is the recommended intake of fluid each day?

A

30 ml/kg/day

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61
Q

Why are minerals important in the diet?

A
  • Electrolytes establish ion gradients across membranes and maintain water balance.
  • Calcium and phosphorous are essential for structure (bones and teeth)
  • Calcium is an important signalling molecule
  • Enzyme co-factors
  • Iron is an essential component of haemaglobin
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62
Q

What are the three disaccharides?

A

Maltose
Lactose
Sucrose

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63
Q

Which sugar is found in fruit?

A

Fructose

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64
Q

What does lipase and glycogen phosphorylase do?

A

Lipases break down triacylglycerol to fatty acids and glycerol

Glycogen phosphorylase cleaves glucose subunits from glycogen.

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65
Q

When is anaerobic glycolysis used?

A

High rates of ATP synthesis are required

Enough oxygen cannot be provided

66
Q

How is NAD+ regenerated for glycolysis to continue in the absence of oxygen?

A

NADH is oxidised to NAD+ as pyruvate is reduced to lactate

67
Q

A calorie in Lay terminology actually means…….

A

1 kilocalorie

68
Q

Fibre provides no nutritional value. Why is it required in a healthy diet?

A

It is necessary for normal GI function.

69
Q

In what form are carbohydrates absorbed into the blood?

A

Monosaccharides

70
Q

Under which certain circumstances may arginine, tyrosine and cysteine be essential amino acids?

A

Pregnant women
Children

Because high rate of protein synthesis

71
Q

What is the difference between saturated, unsaturated fat and trans fat?

A

Saturated fat- all single bonds in fatty acid chains, liquid at room temp
Unsaturated fat- one or more double bonds present in fatty acid chains, solid at room temp
Trans fat- hydrogen on either side of the double bond in fatty acid chain (link between trans fat and chd)

72
Q

What do routine maintenance IV fluids contain?

A

Na+, K+, Cl- 1mmol/kg/day each

Water 30ml/kg/day

73
Q

What is the major role of electrolytes in the body? (Eg. Na+ K+ Cl-)

A

Establish ion gradients across membranes and maintain water balance

74
Q

What are calcium and phosphorous essential for?

A

Essential for structure (bones and teeth)

Calcium is an important signalling molecule

75
Q

What are the roles of minerals?

A

Electrolytes (Na+ K+ Cl-) - establish ion gradients across membranes and maintain osmotic balance

Calcium and phosphorous- important for structure

Calcium- important signalling molecule

Other minerals- co-factors for enzymes

76
Q

What is pellagra and what is it caused by?

A

Niacin deficiency B3

Pellagra =
Dermatitis
Diarrhoea
Dementia

77
Q

Which vitamin deficiencies are associated with anaemia?

A

B12 B6 and folate

78
Q

How do we know the nutrient requirements of different groups?

A

Dietary reference values published by SACN - series of estimates of amount of energy and nutrients required by different groups depending on age, gender and level of physical activity.
Reference nutrient intake (RNI) - used for protein, vitamins and minerals
Estimated average requirement (EAR) - used for energy
Lower reference nutrient intake (LNRI) - intakes below LRNI are insufficient for most people

79
Q

What is the approximate energy requirements for:
A)70kg adult male
B)58kg adult female

A

A) 12,000 kJ/day

B) 9,500 kJ/day

80
Q

What is obesity?

A

Obesity is excessive fat accumulation in adipose tissue which impairs health.
Usually measured using BMI (>30)

81
Q

What diseases is obesity associated with?

A

Some cancers
CVD
Type 2 diabetes

82
Q

What does energy deficiency lead to?

A

Energy deficiency leads to
Glycogen stores/phosphocreatine stores depleted
Adipose tissue fat stores depleted
Muscle proteins break down for energy

83
Q

What is the difference between an endergonic reaction and an exergonic reaction?

A

Energy input> energy released = endergonic

Energy input< energy released = exergonic

84
Q

_______ energy is used to drive all energy-requiring activity in cells.
How is this energy released?

A

Chemical bond energy

Chemical bond energy is released by oxidation

85
Q

Why is the BMR lower for women than men of the same weight?

A

Women have more adipose tissue that is less metabolically active than lean tissue.

86
Q

What is basal metabolic rate controlled by?

A

Thyroid hormones

87
Q

Excessive intake of saturated OR unsaturated fat is associated with high blood cholesterol and a number of pathological conditions including heart disease??

A

Saturated - derived from animal sources

88
Q

Which cells require a constant supply of glucose as a source of energy?

A

Brain cells

Red blood cells

89
Q

Which tissue has the greatest glycogen content in terms of mass?

A

Skeletal muscle

90
Q

Which effect would the hormone glucagon have on the enzyme glucagon synthase in the liver?

A

Decrease in activity

91
Q

Which effect would the hormone insulin have on the enzyme glycogen phosphorylase?

A

Decrease in activity

92
Q

How is energy stored?

A

Creatine phosphate- muscle (few seconds worth)
Glycogen - liver (minutes or hours depending on activity)
Fat - adipose tissue (long term stores, about 40 days)

93
Q

Sugars are hydrophilic and partially oxidised. What does this mean?

A

Hydrophilic=They are water soluble so do not ready cross the phospholipid bilayer of cells.
Partially oxidised=They need less oxygen than fatty acids for complete oxidation.

94
Q

Which enzymes are present on the brush border of epithelial cells in the small intestine?

A

Disaccharidases:

  • lactase (lactose)
  • sucrase (sucrose)
  • isomaltase (alpha 1-6 bonds in maltose )
  • pancreatic amylase (alpha 1-4 bonds in maltose)
95
Q

How are monosaccharides absorbed into the epithelial cells of the small intestine?

A

Active transport
Via sodium-dependent glucose transporter 1 (SGLT1)
Co-transports 2 Na+ for every glucose molecule

96
Q

How are monosaccharides absorbed into the blood stream from the small intestine?

A

Basolateral side of epithelial cels
Facilitated diffusion
Via transport protein GLUT2

97
Q

How are monosaccharides absorbed into cells from the blood?

A

Facilitated diffusion
Via GLUT1-GLUT5

The affinity for glucose and relative activities of these glucose transport proteins differ between tissues and reflect differences in the requirements of the tissues for glucose

98
Q

Which GLUT protein is insulin regulated?

A

GLUT 4
High levels of insulin increase the uptake of glucose into these tissues by increasing the number of glucose transport proteins in the plasma membrane.

99
Q

What is the difference between congenital, primary and secondary lactase deficiency?

A

Congenital
Autosomal recessive defect in lactase gene

Primary
Absence of lactase persistence allele- lactase enzyme only present in early childhood when being breast fed

Secondary
Caused by injury to the small intestine eg. Gastroenteritis
Generally reversible

100
Q

Why do people with lactose intolerance get diarrhoea?

A

In individuals with a lack of lactase, lactose that is ingested in dairy produce will persist into the colon where bacteria can break it down. The presence of lactose in the lumen of the colon increases the osmotic pressure of the contents and will draw water into the lumen, causing diarrhoea.

101
Q

Why do people with lactose intolerance get bloating/cramps and flatulence?

A

In individuals with a lack of lactase, lactose that is ingested in dairy produce will persist into the colon where bacteria can break it downColonic bacteria can produce hydrogen, carbon dioxide and methane gasses from lactose, causing feelings of bloating and discomfort.

102
Q

Which tissues can remove glucose, galactose and fructose from the blood?

A

All of them.

103
Q

Which tissues can metabolise glucose, galactose and fructose?

A

All tissues metabolise glucose

The liver is the major site of fructose and galactose metabolism.

104
Q

Why is it particularly important to maintain the levels of glucose in the blood rather than galactose or fructose?

A

Glucose is the major blood sugar and its concentration is normally held relatively constant because some tissues have an absolute requirement for glucose and the rate of glucose uptake into these tissues is dependent on its concentration in the blood.

105
Q

Which cells have an absolute requirement for glucose?

A 
Red blood cells
Neutrophils
Innermost cells of kidney medulla
Lens of eye
CNS prefers glucose but can use ketone bodies
106
Q

Which pathways can glucose enter once in tissues?

A

Glycolysis
Pentose phosphate pathway
Conversion to glycogen for storage
Conversion to other sugars such as galactose
importance of these pathways varies in different tissues

107
Q

Which steps in glycolysis are irreversible and hence rate-determining steps? Which enzymes control these steps?

A
  1. Hexokinase/glucokinase
  2. Phosphofructokinase-1
  3. Pyruvate kinase
108
Q

What does hexokinase/glucokinase do?

A

Glucose + ATP —> glucose 6-phosphate + ADP

109
Q

What does phosphorylation of glucose do?

A
  • Makes glucose negatively charged- prevents it crossing the plasma membrane
  • Increases the reactivity of the sugar so that it can be metabolised by several pathways: glycolysis, glycogen formation and pentose phosphate
  • Allows formation of compounds with high phosphoryl-group transfer phosphate group to ADP to form ATP
110
Q

Why is phosphofructokinase a key regulator of glycolysis and how is this enzyme regulated?

A 
It regulates the committing step- after this step glucose can only complete glycolysis 
--->Allosteric regulation (muscle) 
Inhibited by high ATP
Stimulated by high AMP
--->Hormonal regulation (liver)
Stimulated by insulin
Inhibited by glucagon
111
Q

In which step is NAD reduced in glycolysis?

A

Step 6

112
Q

Why does NADH produced in reaction 6 need to be reoxidised for glycolysis to continue?

How does this occur?

A

The total amount of NAD+ and NADH in the cell is fixed.

In the presence of oxygen and mitochondria, electron transport is PHASE 4 of metabolism.

In cells that lack mitochondria or in the absence of adequate oxygen, the lactate dehydrogenase reaction.

113
Q

In which steps of glycolysis is ATP synthesised and how?

A

Step 7 and step 10

substrate level phosphorylation

114
Q

How is pyruvate kinase regulated?

A

High insulin:glucagon ratio stimulates pyruvate kinase

115
Q

What are the products of glycolysis?

A

2 pyruvate
2 ATP
2 NADH
2H+

116
Q

Which intermediate in glycolysis can be converted to glycerol phosphate and what is this used for?

A

Dihydroxyacetone-P (formed from in step 4 of glycolysis)

Glycerol phosphate is required for the synthesis of triacylglycerols in liver and adipose tissue.

117
Q

Why is the production adipose tissue dependent on an adequate rate of glycolysis?

A

Glycerol phosphate is required for the synthesis of triacylglycerols in adipose tissue and the liver.

The only method by which glycerol phosphate is produced in adipose tissue is from dihydroxyacetone-P (intermediate in glycolysis produced in step 4) because glycerol kinase is missing in adipose tissue.

118
Q

Which step and intermediate of glycolysis is important for the function of red blood cells?

A

Step 6.
1,3 bis phosphoglycerate produced
This can be converted to 2,3 bisphosphoglycerate which is an important regulator for the oxygen affinity of haemoglobin.
(Increased BPG decreases affinity of haemoglobin for oxygen)

119
Q

What reaction does lactate dehydrogenase catalyse?

A

NADH + H+ + pyruvate —> NAD+ + lactate
In all tissues

And the other way round in the heart, liver and kidneys

120
Q

Where is lactate that is released into the circulation transported to?

A

Heart muscle
Liver
Kidney

121
Q

What happens to lactate in the heart?

A

Lactate is converted to pyruvate

Pyruvate is oxidised to carbon dioxide to release energy

122
Q

What happens to lactate in the liver and kidneys?

A

Lactate is converted to pyruvate.

Pyruvate is converted to glucose (gluconeogenesis)

123
Q

What should the normal lactate concentration in the blood be?

A

<1mmol/L

124
Q

Why might lactate concentration in the bloodstream rise?

A 
Increased production:
Strenuous exercise
Hearty eating
Shock 
Congestive heart disease

Decreased utilisation:
Liver disease
Thiamine deficiency
Lactate dehydrogenase deficiency

Decreased disposal by kidneys:
Above 5mM

125
Q

A high lactate concentration is a critical marker in an acutely unwell patient. Above what concentration is this?

A

> 5mM
Because this is above the renal threshold for excretion
Blood pH is lowered

126
Q

What is the overall reaction for galactose metabolism?

A

Galactose + ATP —> glucose 6- phosphate + ADP

Glucose 6- phosphate enters glycolysis at step 3.

127
Q

Is our only source of galactose our diet?

A

No. The epimerise reaction is reversible enabling galactose to be synthesised from glucose via UDP-glucose. This is important during lactation when breast tissue is synthesising large amounts of lactose for milk production.

128
Q

What happens when there is an accumulation of galactose in tissues?

A

Cataracts
Glaucoma
Liver/kidney/brain damage

129
Q

What is the overall equation for fructose metabolism?

A

Fructose + ATP —> 2 glyceraldehyde-3-phosphate + ADP

Glyceraldehyde-3-P enters glycolysis at step 6.

130
Q

Which enzymes are involved in metabolism of galactose?

A

Galactokinase
Uridyl transferase
UDP-galactose epimerase

131
Q

What enzymes are involved in fructose metabolism?

A

Fructokinase and aldolase

132
Q

What is the difference in clinical effects of fructokinase deficiency and aldolase deficiency?

A

Fructokinase deficiency —> essential fructosuria
Fructose in urine - no clinical signs

Aldolase deficiency —> fructose intolerance
Fructose 1-P accumulates in liver leading to liver damage

133
Q

In which tissues is the pentose phosphate pathway important in?

A

Liver
Red blood cells
Adipose tissue

134
Q

What are the functions of the pentose phosphate pathway?

A

Produce NADPH in the cytoplasm. Roles of NADPH include:

  • reducing power for anabolic processes eg. Lipid synthesis
  • maintaining S-H groups on cysteine residues in proteins
  • various detoxification mechanisms
  • recycles glutathione to its active reduced form

Produce C5 sugar ribose
-synthesis of DNA and RNA nucleotides - this pathway has a high activity in dividing tissues

135
Q

Which enzyme is the pentose phosphate pathway regulated by and what is the activity of this enzyme regulated by?

A

Glucose-6-phosphate dehydrogenase

Activity of this enzyme is controlled by:
-NADP+/NADPH ratio in cell
NADP+ activates pathway
NADPH inhibits pathway

136
Q

What is glutathione and what is essential for it to function?

A

Glutathione is a tripeptide synthesised in the body. The structural integrity and functional activity of key proteins in cells depends on its activity.

It protects against oxidative damage (free radicals) and in order to do this it requires NADPH to recycle it to its active reduced form.

137
Q

What are the consequences of glucose 6-phosphate dehydrogenase deficiency?

A
  • Limits the amount of NADPH
  • NADPH is required for the reduction of oxidised glutathione back to its reduced form.
  • Lower levels of reduced glutathione leaves the cell susceptible to oxidative damage.
  • Red blood cells are particularly affected since G6PDH pentose phosphate pathway is the only source of NADPH here
  • Haemoglobin becomes cross-linked from oxidative damage and forms Heinz bodies
  • Haemolytic anaemia
138
Q

How is pyruvate metabolised?

A

It is converted to acetyl coA before entering stage 3 of carbonise by pyruvate dehydrogenase.

139
Q

Can the conversion of pyruvate to acetyl coA be reversed?

A

No
Loss of CO2 from pyruvate is irreversible
Acetyl coA cannot be converted to pyruvate and therefore cannot be converted to glucose by the process of gluconeogenesis

140
Q

How is pyruvate dehydrogenase regulated?

A

—>Under certain conditions, acetyl CoA from the beta oxidation of fatty acids rather than from glucose is used in stage 3 of catabolism- acetyl coA inhibits PDH allosterically
—>The reaction is sensitive to the energy status of the cell
Inhibited by ATP and NADH
Stimulated by ADP and AMP
—>PDH is activated when there is plenty of glucose- insulin activates PDH by promoting its dephosphorylation

141
Q

What vitamin deficiency affects the activity of pyruvate dehydrogenase?

A

Vitamin B deficiency

142
Q

How can glycolysis be used to view malignant tumours?

A

Rate of glycolysis is up to 200 times greater in cancer
Measure of uptake of FDG - radioactive modified hexokinase substrate
Imagining with PET

143
Q

Which phosphate group on ATP is hydrolysed when energy is needed to drive cellular work?

A

Gamma-phosphate

144
Q

In which type of reaction would the change in Gibbs free energy be less than 0?

A

Exergonic - the products of the reaction have a lower Gibbs free energy than the reactions so delta GF would be negative

145
Q

Which substances is used to supply the electron transport chain with high energy electrons derived from metabolic substrates?

A

NADH

FADH2

146
Q

When ATP levels are high in skeletal muscle, energy may be temporarily stored in which substance?

A

Phosphocreatine can be used to store phosphate bond energy which can be used in the first few seconds of vigorous exercise

147
Q

What is the official SI unit of food energy?

A

Kilojoules

148
Q

Name a carbohydrate that is a source of dietary fibre.

A

Cellulose - major component
Lignin
Pectins
Gums

149
Q

A 40 year old woman has a BMI index of 29.0 kg/m2. What would she be classified as?

A

Overweight (25-29.9)

150
Q

A 20 year old man weights 100kg and is 200cm tall. What is his BMI?

A

25kg/m2

151
Q

What is the chemical formulae for glucose?

A

C6 H12 O6

152
Q

List three main components of the diet that can be metabolised for energy.

A

Carbohydrates
Amino acids
Fatty acids

153
Q

In what cellular compartment does glycolysis occur?

A

Cytosol

154
Q

After glucose is phosphorylated to glucose 6 phosphate by hexokinase, what pathways can it undergo?

A

Glycolysis
Or
Pentose phosphate pathway

155
Q

What is the difference between the function of NADH and NADPH?

A

NADH —> feeds into electron transport chain

NADPH —> reducing power for anabolic pathways (fatty acid synthesis, steroid synthesis, reduction of glutathione)

156
Q

When is the pentose phosphate reaction activated?

A

When the cell has high energy levels
High [NADH]
Allosteric regulation of enzyme in step 6 of glycolysis
Less glucose 6-phosphate enters glycolysis
More glucose 6-phosphate enters pentose phosphate reaction

157
Q

What is the difference between Kwashiorkor and Marasmus?

A

Kwashiorkor
Pathology:
Energy deficiency leads to
1. Glycogen stores/phosphocreatine stores depleted
2. Adipose tissue fat stores depleted
3. Muscle proteins break down for energy

Marasmus
Pathology:
Protein deficiency leads to oedema
Less plasma proteins produced (particularly albumin in the liver)
Reduced oncotic pressure in capillaries
Less interstitial returns to capillaries at venule end
Fluid collects in cavities leading to oedema

158
Q
  • Emancipated with obvious signs of muscle wasting
  • Loss of body fat
  • No oedema
  • Hair is thin and dry
  • Diarrhoea
  • Anaemia

Diagnosis?

A

Marasmus

159
Q 
Signs: 
• Apathetic 
• Lethargic
• Anorexic (loss of appetite)
• Generalised oedema 
• Abdomen distended
• Hepatomegaly
• Ascites 
• Serum albumin low 
• Anaemia

Diagnosis?

A

Kwashikor

160
Q

Explain the clinical consequences of severe protein deficiency in children.

A

Protein deficiency results in an inadequate intake of essential amino acids. This leads to a reduced rate of protein synthesis and a reduced rate of synthesis of other nitrogen containing compounds. The signs and symptoms could include:
 Growth failure (height and weight below normal).
 Impaired physical development (tiredness, weakness and
poor exercise tolerance due to reduced muscle mass).
 Impaired mental development (low IQ).
 Negative nitrogen balance due to Nin < Nout
 Oedema due to reduced albumin synthesis in the liver.
 Increased risk of infection due to reduced immunoglobulin
synthesis.
 Anaemia due to reduced haemoglobin synthesis.
 Fatty liver due to reduced lipoprotein synthesis.

161
Q

Explain the biological role of ATO?

A

ATP acts as a carrier of free energy from energy releasing reactions to energy requiring reactions. The free energy available when fuel molecules are oxidised during catabolism is used to drive the synthesis of ATP from ADP and Pi

162
Q

Where in the small intestine does thee digestion of maltose, dextrin and dietary disaccharidases occur?

A

Duodenum and jejunum

zESA2 (21 decks)

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