BIOL10002 Lecture Notes - Lecture 21: Scurvy, Cellular Respiration, Thiamine
Lecture 21: Significance of Nutrition to Health
Epigenetics: the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself; nutrients
are constantly interacting with your gene expression patterns, modifying expression through epigenetic mechanisms
Nutrients act as environmental signals: regulate gene expression
Heterotrophs: animals cannot synthesize organic compounds/make
their carbon skeletons, so must eat plants and other animals to obtain
them
Plants can synthesize organic compounds/make their carbon skeletons:
autotrophs
Organic compounds: carbon skeletons
Example of a required carbon skeleton: acetyl group: animals cannot
make acetyl groups from CHO, they obtain them from metabolizing
carbohydrates, fats or proteins from food; animals then use acetyl
groups to build more complex organic molecules
What we need
Major nutrients to be used as building blocks to make more complex
molecules and to provide metabolic energy
Carbohydrates: as simple or complex sugars (monosaccharides,
disaccharides or polysaccharides such as starch): provide energy via
ATP, stored as glycogen
Protein: nitrogenous organic compounds which have large molecules
composed of one or more long chains of amino acids; essential part of
all living organisms, especially as structural components of body tissue
and as enzymes and antibodies, 4.1kcal/g
Fat: provide more energy via ATP
Other essential nutrients:
Mineral elements in different amounts:
Macronutrients: a chemical element/type of food required in large
amounts in the diet: carbs, protein, fat, Ca, Mg, P, K, Na, S
Micronutrients: chemical element (eg. mineral) or substance needed in
micrograms/small amounts for normal growth & development: Cr, Co,
F, I, Fe, Mn, Mo, Se, Zn
Vitamins: organic molecules that must be obtained from food; function
as coenzymes or parts of coenzymes
Vitamin C deficiency: scurvy
B1, thiamin: coenzyme in cellular respiration
● deficiency: extreme muscle weakness (beriberi), loss of
appetite, tingling sensations, irritability, weight loss,
constipation, forgetfulness & fatigue
● prevented by a healthy diet
● beriberi occurs in people whose staple diet consists mainly of
polished white rice, which contains little or no thiamine
therefore the disease has been seen in people in Asian
countries (especially 19th century and before) and in chronic
alcoholics with impaired liver function
C, ascorbic acid: aids formation of connective tissues, prevents
oxidation of cellular constituents
● deficiency leads to scurvy, slow healing, exhaustion &
weakness, swelling of the limbs, softening of the gums,
excessive bruising, foul breath, diarrhea, lung & kidney
problems, depression, poor bone growth
● caused by lack of fresh fruit & vegetables
Water soluble vitamins: rapidly destroyed by alcohol, very hard to
overdose on water soluble vitamins as after tissues become saturated,
you simply pass them out in your urine
Fat-soluble vitamins: unlike water-soluble vitamins, fat-soluble vitamins
(stored in the liver) can become toxic at high concentrations
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D, calciferol: functions in absorption of calcium & phosphorus
● deficiency: rickets, induces depression
Rickets: lack of vitamin D & calcium: affects calcium absorption, a
disease caused in children with low vitamin D characterized by
imperfect calcification, softening, and distortion of the bones typically
resulting in bow legs
Eight essential amino acids: deficiency impairs protein synthesis
amino acids that cannot be synthesized from scratch by the organism, must be supplied in its diet; 5 are dispensable in humans: can be
synthesized in sufficient quantities in the body
Essential fatty acids: fatty acids that humans and other animals must ingest because the body requires them for good health but cannot
synthesize them, notably linoleic acid: needed to synthesize other fatty acids & prostaglandins (polyunsaturated essential fatty acid present as a
glyceride in linseed oil and other oils and essential in the human diet)
Ingestion or feeding: food can be acquired in different ways and in
different forms: saprobes, detritivores, filter feeders, fluid feeders,
predators (herbivores, carnivores, omnivores)
saprobes: obtain carbon & energy directly from dead organic matter
e.g. bacteria or fungi
detritivores: obtain energy from the waste products of other organisms
filter feeders: trap tiny particles or organisms suspended in water, e.g.
primitive fish, molluscs, baleen whales
predators: catch & kill another organism for food: carnivores,
omnivores, herbivores
Stored energy rate in humans: the energy in chemical bonds is
measured in calories (kcal or joules)
● fats yield 9.5kcal/g, carbohydrates 4.2kcal/g, proteins
approx. 4.1kcal/g
● females need: 1300-1500 kcal/day at rest
● males: 1600-1800 kcal/day at rest
Units of energy:
1 calorie is the amount of energy required to raise the temperature of 1
gm of water by 1 degree celsius (very small amount of energy)
dieticians typically refer kcal (kilocalories)l i.e. 1000 cal; what is seen as
cal when diets are being discussed
1 Cal = 4.2 KJoules
capital C (Cal) = represents 1 kcal
in terms of nutrition: 1 Cal ≠1 Cal
Nutrition requirements: animal with insufficient caloric intake:
undernourished, must metabolize stored glycogen, fat, and finally its
own protein
First store: glycogen (polysaccharide stored in liver & muscle):
substance deposited in bodily tissues as a store of carbohydrates;
forms glucose on hydrolysis
To store carbohydrates, also need to hold a lot of water, therefore
initial weight loss is usually just water weight gone with the loss of
glycogen; carbohydrates stored as glycogen which has a very high
water content and so is heavy, hence initial rapid weight loss when you
fast
Last measure: proteins used as energy during starvation
Obesity: major health issue
Australia: approximately 50% of men and 33% of women
overweight/obese and about 16% of adolescents, 400 million obese
worldwide
comorbidities: cardiovascular disease, hypertension, type 2 diabetes,
Female obesity:
fertility issues:
● anovulation: when ovaries don't release an oocyte during a
menstrual cycle, infertility
● menstrual cycle changes
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cancer
genetics can play a significant role in comorbidities, eg. a seemingly
obese, smoker, unhealthy man may live longer than a healthier
counterpart due to genetics
a prolonged increase in fat and/or carbohydrate intake and/or a
reduced amount of physical activity (an energy imbalance), can lead to
obesity
social & lifestyle factors as well as a genetic background
obesity in mice & leptin: single gene mutation leads to obesity in mice:
eats enormous amounts of food, becomes obese, wildtype ob allele
codes for protein: leptin: mice with mutations on both ob genes cannot
produce leptin therefore unaware when they have sufficient amounts of
fat stored
leptin: involved in the long term regulation of body weight, produced
primarily by fat cells, circulates the blood and acts on different tissues
including the hypothalamus, skeletal muscle and liver, provides
information about the status of body fat reserves to the brain
experiment: injection of recombinant leptin into ob/ob mice resulted in
reduced appetite & weight loss, receptors for leptin are found in the
regions of the hypothalamus that are involved in the control of hunger -
ventromedial hypothalamus
leptin to treat obesity?: a few obese people do not produce leptin, and
injections can reduce their appetites and enable weight loss, most
obese people have higher than normal leptin levels: problem with
receptors for leptin in the hypothalamus; leptin decreases its own
receptors; leptin receptors have reduced sensitivity to leptin and
therefore leptin cannot have its appetite suppressing effects
● PCOS: polycystic ovary syndrome, irregular or no period,
acne, obesity & excessive hair growth
pregnancy complications
● preeclampsia: a condition in pregnancy characterized by high
blood pressure, sometimes with fluid retention and
proteinuria
● gestational diabetes
● birth defects
● preterm/cesarean delivery
● early and recurrent miscarriage
Male obesity & fertility:
● infertility treatment
● longer time to conceive
● hormonal imbalances
● sperm quality affected
Being obese is not consistent with having a family, children of obese
parents are compromised
Lecture 22: Regulation of Digestion
Food must be subjected to physical and chemical changes for absorption; actions of the digestive tract and its digestive glands
Major food nutrients are large macromolecules which cannot pass through the lining of the intestine therefore must be broken down to small
molecules that can pass through cell membranes
Digestion converts large organic molecules present in food into small molecules that can pass through cell membranes
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Document Summary
Epigenetics: the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself; nutrients are constantly interacting with your gene expression patterns, modifying expression through epigenetic mechanisms. Nutrients act as environmental signals: regulate gene expression. Heterotrophs: animals cannot synthesize organic compounds/make their carbon skeletons, so must eat plants and other animals to obtain them. Plants can synthesize organic compounds/make their carbon skeletons: autotrophs. Example of a required carbon skeleton: acetyl group: animals cannot make acetyl groups from cho, they obtain them from metabolizing carbohydrates, fats or proteins from food; animals then use acetyl groups to build more complex organic molecules. Major nutrients to be used as building blocks to make more complex molecules and to provide metabolic energy. Carbohydrates: as simple or complex sugars (monosaccharides, disaccharides or polysaccharides such as starch): provide energy via.
