Session 1 Lecture Notes Flashcards
What do catabolic processes do?
Break down molecules to release energy in the form of reducing power
Energy from catabolic processes drives anabolic processes
What do anabolic processes do?
Use energy and raw materials to make larger molecules for growth and maintenance
What is biosynthetic work?
Synthesis of cellular components
What percentage of the brains’ energy is used for transport work and give an example
50%
NA, K ATPase
What form of energy is used in our bodies to drive every biological reaction?
Chemical bond energy
What are the 3 components of ATP?
Adenine ring
Ribose sugar
3 phosphate groups (alpha beta and gamma)
Where is the energy source obtained from in ATP?
In the last phosphodiester bond - the energy is released when the bond is broken
Using oxidation give three examples of where energy can be obtained?
Carbohydrates
Lipids
Protein - in times of need
Alcohol - but dangerous
What is the official unit of food energy?
Kilojoules (kJ)
What does calorie actually refer to? How many calories in a kilojoule?
Calorie (kcal) = kilocalorie
So 1 calorie is actually 1000 calories
1 calorie = 4.2 kilojoules
What is fibre necessary for?
Maintaining normal GI function
What is the formula for carbohydrate?
What does carbohydrate contain?
(CH20)n
Aldehyde or keto groups
Multiple OH groups
What is a monosaccharide?
A single sugar unit e.g. glucose
How many carbons do the following monosaccharides contain?
Triose sugar
Pentose sugar
Hexose sugar
What is glucose classified as?
Triose = 3 carbons
Pentose = 5 carbons
Hexose = 6 carbons
Glucose contains 6 carbons so is a hexose sugar
What are disaccharides?
2 simple sugar units linked together (2 monosaccharides)
What are oligosaccharides?
3-12 simple sugar units linked together
What are polysaccharides? Give 3 examples
More than 10 simple sugar units linked together - up to thousands
e.g. cellulose, starch and glycogen
What 2 sugars make up the disaccharide sucrose (table sugar)?
What 2 sugars make up the disaccharide lactose (milk sugar)?
Sucrose = glucose-fructose Lactose = galactose-glucose
What is fructose and what form of sugar is it?
Fruit sugar
Monosaccharide
Maltose is a disaccharide. What sugars compose it?
Glucose-glucose
What does digestion break protein down into?
Amino acids which enter the bloodstream
What are essential amino acids and how many are there?
They are AAs that we cannot synthesise (can only be obtained from our diet)
9 out of 20 AAs in our body are essential
Try and name as many of the essential AAs as you can
Clue = If learned this huge list may prove truly valuable
Isoleucine Lysine Threonine Histidine Leucine Methionine Phenylalanine Tryptophan Valine
What does conditionally essential mean when referring to AAs?
They are essential at periods of rapid growth
What 3 AAs may pregnant women and children also require?
Arginine
Tyrosine
Cysteine
As they cannot be synthesised at the required rate
Give an example of a high quality and low quality source of protein. Why are they classified in this way?
High = animal origin
Low = plant origin
High contain all essential AAs
Low are deficient in one or more essential AAs
What are triacylglycerols?
3 fatty acids esterified to one glycerol (compose lipids)
What are the fat soluble vitamins?
A D E and K
Give 2 examples of essential fatty acids
Linoleic
Linolenic
What are the 3 major electrolytes?
Sodium
Potassium
Chloride
What is the routine maintenance (IV fluids) for
1) the key electrolytes
2) water
1) 1 mmol per kg per day (of each = sodium, potassium and chloride)
2) 30ml per kg per day
What causes the disease pellegra?
Deficiency in niacin vitamin
Deficiencies in which 2 vitamins can cause anaemia?
B12
Folate
Why can’t humans break down the polysaccharide cellulose? (a polymer of glucose)
Because humans don’t have the enzymes needed to break down the beta-1,4 links in cellulose
What is the RNI and what is it used for?
Reference Nutrient Intake
Used for proteins, vitamins and minerals
What is EAR and what is it used for?
Estimated Average Requirement
Used for energy
Is the approximate value that the mean person requires (50% will require more)
What is LRNI?
Lower reference nutrient intake
Intakes below this are insufficient for most people
It is the what the average person at 2.5% on graph requires
What is RNI?
Reference nutrient intake
It is what the average person at 97.5% on the graph requires
How is daily energy expenditure calculated?
3 measurements
1) BMR - basal metabolic rate
2) DIT - diet induced thermogenesis (energy to process food)
3) PAL - physical activity levels
How is BMI calculated?
Body Mass Index
BMI = weight (kg) / height2 (m2)
What is the normal fasting plasma concentration for glucose?
3.3-6.0 mmol/L
What is the enzyme in saliva and what does it do?
Amylase
Breaks down starch and glycogen into dextrins
What is broken down in the small intestine and what are the enzymes involved?
Amylase is secreted through ducts in the pancreas into the duodenum which breaks down monosaccharides (breaks down the alpha-1,4 bonds)
The cells attached to the villi of epithelium secrete disaccharidases which break down glucose lactose and maltase
What causes a lactose intolerance?
Lack of enzyme lactase so the lactose is not broken down properly
Explain the following:
1) Primary lactose deficiency
2) Secondary lactose deficiency
3) Congenital lactose deficiency
1) an absence of lactase persistence allele (can’t break down lactose)
2) caused by injury to small intestine
3) extremely rare - autosomal recessive defect in lactase gene means baby cannot digest breast milk
Active transport is used in small intestines to move monosaccharides into bloodstream across 2 sides of the epithelium lumen. What are these sides and what are the transporters?
1) Apical side (facing lumen of small intestines) = the SGLT1 transporter is used (sodium dependent glucose transporter 1) where co transport of 2 sodium ions with 1 glucose
2) Basolateral side = the GLUT2 transporter used to move into blood supply (uniport)
How is glucose taken up in the cells from the blood?
Via facilitated diffusion (GLUT1-5 transporters)
Where are GLUT2 tranporters primarily found?
In the kidney, liver, pancreatic beta cells and small intestine
Where are GLUT4 transporters primarily found?
In adipose tissue, skeletal muscle and insulin regulated
Give 4 examples of cells for which glucose is an absolute requirement (only source of energy)
1) Erythrocytes
2) Neutrophils
3) Innermost cells of kidney medulla
4) Lens of the eye
What is glycolysis?
Oxidation of glucose (monosaccharide) to 2 pyruvate molecules
What is the net gain of ATP in glycolysis?
2
First reaction in glucose catabolism uses 2 ATP molecules
2nd reaction creates 4 ATP molecules
How many units of NADH are produced during glycolysis?
2 NADH molecules per 1 molecule of glucose
What are the 3 key enzymes in glycolysis and what intermediaries do they convert?
- Hexokinase (glucokinase in liver)
Converts glucose into Glucose-6-phosphate - Phosphofructokinase-1
Concerts Fructose-6-phosphate into Fructose 1,6-bis-phosphate - Pyruvate kinase
Coverts Phosphoenolpyruvate into Pyruvate
What does phosphorylation of glucose to glucose-6-phosphate do?
Makes glucose negatively charged
Prevents glucose moving back across cell down concentration gradient
What does having a large negative delta G mean?
That the reaction is irreversible
What enzyme is the key regulator of glycolysis?
Phosphofructokinase
In which 2 ways is phosphofructokinase regulated?
- Allosteric regulation
(High ATP = inhibits PFK activity, high AMP = stimulates PFK activity) - Hormonal regulation
(Large intake of nutrients = stimulation of activity of PFK by insulin, and inhibited by glucagon)
Explain how levels of NADH and NAD+ are metabolically regulates
High levels of NADH or low levels of NAD+ = high energy signals
Cause inhibition of glycolysis
How is the enzyme pyruvate kinase regulated?
Activity of enzyme increases when there is a high insulin:glucagon ratio e.g. high levels of insulin and low levels of glucagon
Where is glucagon produced and what does it do?
It is a hormone produced by alpha cells of the pancreas
It raises the levels of glucose in the bloodstream (causes liver to convert stores glycogen into glucose)
Where is insulin produced and what does it do?
It is a hormone produced by beta cells of the pancreatic islets of langerhans
Promotes the absorption of glucose and anabolism (converting glucose into glycogen stores)
NAD+ is needed in glycolysis as it converts to NADH. NAD+ can be regenerated from 2 routes what are they?
Regenerated from NADH
Regenerated by lactate dehydrogenase (LDH)
What does lactate dehydrogenase convert?
NADH + H+ + pyruvate –> NAD+ + lactate
What is the process called when pyruvate is converted back to glucose and where does this take place?
Glucogenesis
In the liver and kidney
What is lactic acidosis and what does it cause?
It is a plasma lactate level of over 5mM (above the renal threshold level = kidneys can no longer excrete it)
It lowers the blood pH
Deficiency in which 3 enzymes can cause galactosaemia?
- Glactokinase
- Uridyl tranferase
- UDP-galactose epimerase
What are the 2 main enzymes involved in metabolising fructose?
Fructokinase
Aldolase
What is essential fructosuria?
Missing enzyme fructokinase
Leads to fructose in urine but no clinical signs
What is fructose intolerance?
Missing enzyme aldolase
Fructose-1 phosphate accumulates in the liver and can lead to liver damage
What enzyme is the start of the pentose phosphate pathway and what does it convert?
Glucose 6 phosphate dehydrogenase enzyme
Converts glucose 6 phosphate to 6-phosphogluconolactone
What is the end product of the pentose phosphate pathway and what does it produce along the way?
Along the way NADPH is produced (needed for fatty acid and steroid biosynthesis)
Pentose phosphate pathway produces ribose 5 phosphate (needed for DNA and RNA synthesis)
