Option C - Human biochemistry

1
Option C - Human biochemistry

• C.1 Diet

2
C.1.1 Requirements of a Healthy
Human Diet

• Water necessary for life, biochemical activities
  within the body

3
Food groups

• 1) milk group-milk, cheese, yoghurt --gtsupplies
  calcium, protein, vit AD
• 2) meat group-meat, fish, poultry, eggs, legumes,
  nuts --gt iron, vit B,energy
• 3)vegetable and fruit group --gtvit AC
• 4)bread and cereal group --gtenergy, vit,
  minerals, protein

4
Carbohydrates

• source of calories (energy), glucose important in
  energy-producing cycles within cells. RDA

5
Proteins-

• enzymes to catalyze the body's chemical
  reactions, hormones, muscle, connective tissue

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Fats ( oils)-

• concentrated source of energy RDA

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Vitamins-
8
Minerals

• Calcium- blood, cells, body fluids, bones (its
  absorption is enhanced by vit D) Magnesium-
  maintains the electric potential across
  nerve-and-muscle-cell membranes
• Phosphorus- bones teeth
• Iodine- essential for functioning of thyroid
  gland
• Iron- hemoglobin, enzymes
• Zinc- part of important enzymes in the body

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Importance of a Balanced Diet

• -deficiency in caloric assumption results in
  deficiency diseases, starvation, or death
• -overnutrition results in obesity, high blood
  pressure, diabetes, heart attacks
• -excess in saturated fat consumption leads to
  rise in blood cholesterol levels- strokes
• -deficiency in protein and minerals- anemia,
  edema, loss of pigment and hair, retarded growth

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C.1.2 Calories and Enthalpy of Combustion

• -calories are the energy content of food
• -energy is stored in chem bonds that link atoms
  and molecules. Energy is captured by the body
  during biochemical reactions involving the
  combustion of nutrients. This energy is used to
  drive life processes of cells.
• Proteins and Carbohydrates- 4kcal/g
• Fat- 9kcal/g
• Alcohol- 7kcal/g

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C.2 Proteins
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C.2.1 2-Amino Acids

• -there are 20 different 2-amino acids
• -they contain an amine group (NH2) on the central
  carbon atom (a), a carboxyl group and different
  R-groups.
• -all amino acids are optically active (not
  needed, but good to know)

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Amino Acid
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C.2.2 POLYPEPTIDES 

• -two amino acids join to form a dipeptide---the
  bond is called PEPTIDE BOND
• -condensation reaction a hydroxyl group is lost
  from one of the amino acids' carboxyl group,
  while the other amino acid loses a H from its
  amine group. (again, a diagram would be good,
  but...)
• -amino acids join to form proteins

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Dehydration Synthesis

• Lets see how amino acids combine to make
  proteins.
• Amino acids combine in the presence of an enzyme
  during dehydration synthesis.

O
H
H
O
H
H
C
C
N
C
C
N
H
H
O
H
O
H
R
R
H2O
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Dehydration Synthesis
H
H
H
H
O
O
C
C
C
C
N
N
H
O
H
R
R
H2O
Peptide Bond

• The compound produced from the dehydration
  synthesis of two amino acids is a dipeptide.
• Water is also produced during the reaction.
• The bond between the carbon atom and the nitrogen
  atom is a peptide bond.
• A polypeptide is a long chain of amino acids
  containing many peptide bonds.
• Proteins can contain two or more polypeptide
  chains.

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C.2.4 PROTEIN STRUCTURE-PRIMARY

• amino acids arranged in linear order

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PROTEIN STRUCTURE -SECONDARY

• -alpha helixcoil of polypeptides, with hydrogen
  bonds between the amide hydrogen atom in one
  peptide and the carbonyl oxygen atom of another
  peptide, at a distance of three amino acids. Coil
  chains are held together by DISULFIDE BONDS
  between adjacent chains.
• -beta-pleated sheet a folded sheet, stabilized
  by hydrogen bonds between the chains. There are
  NO disulfide bonds in this structure.

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Alpha Helix
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Secondary Structure- b Sheet
Carbonyl C
H Bond
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PROTEIN STRUCTURE TERTIARY-

• folded structure of chains of amino acids. 4
  types of interactions
• 1) Ionic bonds between R and R-
• 2) H-bonds between partial - and partial
  R-groups
• 3) Disulfide bonds
• 4) Hydrophobic interactions- non polar R-groups
  tend to stay close together because repelled
  polar substances surrounding proteins.

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PROTEIN STRUCTUREQUATERNARY

• more than one polypeptide chain join to form a
  protein--several folded chains joined by
  disulfide bonds (eg. hemoglobin)

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Quaternary Structure
The classic example- hemoglobin a2-b2
END OF PART 1
B/T- Figure 3.7
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Disulfide Bonding
V/V/P- Figure 16.6
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Protein Separations

• Paper Chromatography
• Electrophoresis

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An Experiment

• The solvent rises up the paper when the two
  touch.
• The spot on the filter paper contains four
  different amino acids.
• Watch what happens when the paper touches the
  solvent in the beaker

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Amino Acid Experiment

• Which amino acid is the most soluble in this
  solvent (1-4)?
• Number 1 is the most soluble. It remains
  dissolved in the solvent longer than the other
  amino acids and travels farther up the paper.
• Which amino acid adheres most tightly to the
  paper (1-4)?
• Number 4 sticks tightly to the paper and does not
  move as far as the other amino acids.

1
2
3
4
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Gel Electrophoresis

• Movement of charged molecules in an electric
  field.
• Polyacrylamide gel provides a porous matrix
• (PAGE Polyacrylamide Gel Electrophoresis)
• Sample is stained to make it visible in the gel.
• Sample placed in wells on the gel.
• Electric field across gel separates molecules.
• Negatively charged molecules travel towards the
  positive terminal and vice-versa.
• Cheap, fast and easy!

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1-D Gel electrophoresis

• Separation in only 1 dimension size.
• Smaller molecules travel further through the gel
  large ones get stuck earlier creating a
  separation.

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1-D cont.

• DNA/RNA are stained with Ethidium Bromide which
  fluoresces under UV light.
• Protein stained with Coomassie Blue which is blue
  in visible light.
• Southern blots (DNA), Northern blots (RNA),
  Western blots (Protein).
• Proteins are treated with the denaturing
  detergent SDS (sodium dodecyl sulfate) which
  coats the protein with negative charges, hence
  SDS-PAGE.

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 C.2.5 FUNCTIONS 

• -structure, eg collagen (fibrous proteins)
• -biological catalysts (eg. enzymes)
• -transport eg. hemoglobin
• -energy source

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Functional Classes of Proteins

• Receptors- sense stimuli, e.g. in neurons
• Channels- control cell contents
• Transport- e.g. hemoglobin in blood
• Storage- e.g. ferritin in liver
• Enzyme- catalyze biochemical reactions
• Cell function- multi-protein machines
• Structural- collagen in skin
• Immune response- antibodies

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Structural Classes of Proteins

• 2. Fibrous Proteins (fibrils, structural
  proteins)
• One dominating secondary structure
• Typically narrow, rod-like shape
• Poor water solubility
• Function in structural roles (e.g. cytoskeleton,
  bone, skin)

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Collagen A Fibrous Protein
Triple Helix
Stabilizing Inter-strand H-bonds
Gly-Pro-Pro Repeat
V/V/P- Figures 6.17/18
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Structural Classes of Proteins

• 3. Membrane Proteins (receptors, channels)
• Inserted into (through) membranes
• Multi-domain- membrane spanning, cytoplasmic, and
  extra-cellular domains
• Poor water solubility
• Function in cell communication (e.g. cell
  signaling, transport)

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C.3 Carbohydrates

• Contain the elements Carbon Hydrogen Oxygen
• There are 3 types
• Monosaccharides
• Disaccharides
• Polysaccharides

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C.3.1 MONOSACCHARIDES

• -all sugars that contain a single carbohydrate
  unit, with an empirical formula CH2O
• -contain a carbolyl group (CO), and at least two
  hydroxyl groups (-OH)
• -eg. -glucose, fructose, galactose

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Monosacharides

• If n3, triose (glyceraldehyde)
• If n5, pentose (fructose, ribose)
• If n6, hexose (glucose, galactose)
• Used for Energy and Building Blocks

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C.3.2 GLUCOSE

• -C6H12O6
• -a main source of energy
• -contains six carbons with an aldehyde group
  (H-CO) on the first and hydroxyl groups on each
  of the remaining carbons
• -in water, the 2nd C and the 6th C form a bond,
  forming a cyclic structure
• -a-glucose hydroxyl group on the sixth carbon is
  DOWN
• -b-glucose it is UP

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Isomerism

• They can exist as isomers
• ? ? glucose

OH
?
?
OH
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Disaccharides

• Formed from two monosaccharides
• Joined by a glycosidic bond
• A condensation reaction
• glucose glucose ? maltose
• glucose galactose ? lactose
• glucose fructose ? sucrose

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C 3.3 Condensation reaction
OH
OH
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Condensation reaction
OH
OH
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Condensation reaction
O
H2O
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Condensation reaction
4
1
O
A disaccharide 1,4 glycosidic bond
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Polysaccharides

• Polymers formed from many monosaccharides
• Three important examples
• Starch
• Glycogen
• Cellulose

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Starch

• Amylopectin
• ?-glucose
• 1,4 and some 1,6 glycosidic bonds
• Branched structure

• Amylose
• ?-glucose
• 1,4 glycosidic bonds
• Spiral structure

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Glycogen

• Insoluble compact store of glucose in animals
• ?-glucose units
• 1,4 and 1,6 glycosidic bonds
• Branched structure

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Cellulose

• Structural polysaccharide in plants
• ?-glucose
• 1,4 glycosidic bonds
• H-bonds link adjacent chains

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C.3.4 FUNCTIONS OF POLYSACCHARIDES

• a number of monosaccharides joined together eg.
  Starch, a polymer of glucose, with formula
  (C6H10O5)n eg. Glycogen, same molecular
  formula--gives glucose when hydrolised, stored in
  liver and muscles as a reserve of carbohydrates.
  (this is not needed)

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• -basic energy sources for living organisms
• -GLYCOGEN- an energy reserve, (stored in liver),
  can break down into glucose when it is needed
• -Precursors for other biologically important
  molecules---i.e. monosaccharides are used to make
  other molecules like glycerol and fatty acids and
  some amino acids.
• -Cellulose-structural material in plants (not in
  syllabus)

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C.4 Fats
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C.4.1 COMPOSITION OF FATS/OILS

• -fatty acids long chain of carbon and hydrogen
  atoms with a carbonyl group at the end (CO)
• -TRIGLYCERIDES molecules formed by the joining
  of three fatty acids to a molecule of glycerol by
  dehydration synthesis.
• -solid at room temperature-"fats"-and liquid at
  room temp- "oils"
• -PHOSPHOLIPIDS- similar to the above, but one or
  to of the fatty acids are replaced by a phosphate
  group,
• -ALL Fats are hydrophobic--contain a high
  proportion of C-H bonds, the carbonyl end of the
  molecule is hydrophilic

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C.4.2 SATURATED/UNSATURATED FATS

• -SATURATED- fats with single bonds (no double
  bonds, not even one), C atoms can hold no more H
  atoms than they already have
• -UNSATURATED- fats with at least one double bond
• -the double bond causes fats (eg triglyceerides)
  to have a lower boiling point-the double bond
  tends to keep the fat flat-linear----usually oils
  at room temp

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Unsaturated Fatty Acids
3 - Octenoic Acid
3, 6 - Octadienoic Acid
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Saturated Fatty Acids
Octanoic Acid
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C.4.3 FAT ADDITION REACTION

• -The extent of unsaturation of a fat---tested by
  I2. By calculating the number of moles that react
  with a fat, the number of double bonds will be
  discovered. This is because the double bonds
  between C atoms are broken, and I bonds itself to
  the C. One I will bond to each former double-bond
  location--every molecule of I2 used indicates one
  double bond.Electrophillic addition R-CC-R I2
  ---gt R-I-C-C-I-R
• -When the reaction occurs, the iodine will become
  clear.

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Iodine Number
Number of iodine (g) absorbed by 100 g of
oil. Molecular weight and iodine number can
calculate the number of double bonds. 1 g of fat
adsorbed 1.5 g of iodine value 150.
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Iodine Value Determination
Excess unreacted ICl
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C.4.4. SOAP

• -Soap is made by the hydrolysis of fats. NaOH is
  added as a source of alkali.
• -3 Na are required to saponify one fat molecule
  (generally a triglyceride). These will replace
  the glycerol, yielding three fatty acids with an
  Na tail.

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Saponification
Saponification - hydrolysis of ester under
alkaline condition.

3

3
62
C.4.5 FUNTIONS

• -Energy source (self-explanatory)
• -Insulation (ditto)
• -Cell membrane-made up of phospholipids

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Function of Lipids

• Formation of protective structures
• Metabolic reserve
• Structural component of cell organelles
• Hormones and signal compounds
• Vitamins

64
 C.5 Vitamins
65
C.5.1 Role in Metabolism

• -Metabolism- all of an organism's biochemical
  reactions
• -In order for reactions to take place in the
  body, catalysts are needed-these are called
  enzymes (see section on enzymes for more info)
• -Enzymes do not work alone, and sometimes require
  the help of coenzymes in order to carry out their
  catalytic functions--gtvitamins function as
  coenzymes (mainly water soluble vitamins)

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C.5.2 Water/Fat Soluble

• -WATER- coenzymes needed in metabolism. eg.
  Vitamin B and C. when in excess, they pass out
  the body in urine
• -FAT-other functions in body (not clear) eg.
  Vitamin A and D. These can be stored in fat
  tissue These vitamins can accumulate to toxic
  levels

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Functions (structures listed in data-booklet) 

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Vitamin A (Retinol

• Vitamin A (Retinol)--at night, light shining on
  the eye strikes a receptor, rodopsin which sends
  an impulse to the brain. vit A is essential in
  the formation of rodopsin.
• Deficiency--night-blindness, xerophthalmia (tear
  glands cease to function)

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Vitamin C

• Vitamin C (ascorbic acid)--essential in the
  formation of connective tissue-collagen. Works as
  a reducing agent to form one of the amino acids
  in the protein collagen
• Deficiency- scorbutus ("scurvy"-connective tissue
  breaks down, hemorrhage)

70
Vitamin D (calciferol)

• important in the production of a hormone involved
  in the metabolism of calcium.
• (2 -OH groups are added) and it functions as a
  hormone which causes the intestines to absorb
  calcium from food.
• Deficiency--rickets (weak bones, low blood
  calcium level)

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Vitamin E
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C.5.4 Food Processing

• -most vitamins are destroyed or altered during
  cooking, especially water soluble vitamins. (fat
  soluble vit are relatively stable)
• -vit B is destroyed during milling processes

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C.6 Hormones

• -organic molecules secreted by one part of the
  organism but having an effect on another. They
  are controlled by the pituitary gland, which is
  controlled by the hypothalamus. Secreted by
  endocrine glands.

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C.6.1 Production/Roles

• -ADRENALIN synthesized from amino acid
  Tyrosinewhen exercise is done, impulses are sent
  for adrenaline to be released into the blood
  stream. It causes blood to be sent into areas of
  more active circulation. Increase in volume of
  blood available. Increase in rate of heart beat,
  stimulated respiration. the breakdown of glycogen
  to glucose is stimulated-raises level of sugar in
  the blood stream.

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C.6.1 Production/Roles

• -THYROXINE iodated amino acid derivative,
  produced by the thyroid gland stimulates growth
  and metabolism

• INSULIN made up of 2 poypeptide chains held
  together by disulfide bonds. Made in the pancreas
  by the Islet of Langerhorn. regulates cellular
  intake of glucose from the blood. It is secreted
  in response to a rise in blood sugar or amino
  acid concentration. It also inhibits the
  breakdown of glycogen in the liver.

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Female Sex Hormones

• pituitary hormones (LH and FSH) are secreted at
  puberty, Estrogen (produced by ovary) stimulates
  an increase in secretion of a hormone, which
  brings about the maturation of the follicle and
  the ovulation. stimulates the development of
  female features breasts, subcuataneous fat,
  menstrual cycle Porgesterone (corpus luteum of
  ovary)- stimulate the endometrium (lining of the
  uterus) to thicken and to secrete a nourishing
  fluid-in preparaton for a fertilized egg.

77
Male Sex Hormones

• Male Testosterone-hormone secreted by the
  testes and the sdrenal glands (above the
  kidneys). During puberty, the pituitary gland
  stimulates the release of a potein ABP, which has
  high affinity for testosterone. stimulates
  development of male features deepening of voice,
  development of male musculature, growth of hair
  on the face and other parts of the body.

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C.6.2 Steroids (see structure in data booklet)

• -a type of lipid (hydrophobic)
• -Structure consist of four contiguous carbon
  rings (the common backbone)
• -Different steroids have different functional
  groups attached to the backbone.

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Sterols
80
Steroids

• Based on a core structure consisting of three
  6-membered rings and one 5-membered ring, all
  fused together
• Cholesterol is the most common steroid in animals
  and precursor for all other steroids in animals
• Steroid hormones serve many functions
• salt balance
• metabolic function
• sexual development

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Steroid Hormone Structures
cholesterol
82

Cholesterol

• Key lipid found in cell membranes
• Precursor to steroid hormones

Sexual Development estradiol testosterone
Metabolic Regulation glucocorticoids
Pregnancy progesterone

Digestion Bile Acids
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C.6.3 Oral Contraceptive

• C.6.3 Oral Contraceptive
• -the "pill" consists of estrogen and progesterone
  hormones (synthetic). The excess of these
  hormones (at a given dosage) will prevent
  ovulation, thus avoiding pregnancy.
• -Negative feedback control--The increased levels
  of estrogen inhibit the levels of LH hormone
  released by the pituitary gland. The drop in LH
  and FSH levels stops the development of the
  endometrium lining-without it the egg cannot
  implant and therefore no pregnancy will occur.

84
C.6.4 Steroid Use and Abuse