Transcript Option C - Human biochemistry C.1 Diet-

Option C - Human biochemistry
C.1 Diet
C.1.1 Requirements of a Healthy
Human Diet:
• Water: necessary for life, biochemical
activities within the body
Food groups:
• 1) milk group-milk, cheese, yoghurt ->supplies calcium, protein, vit A&D
• 2) meat group-meat, fish, poultry, eggs,
legumes, nuts --> iron, vit B,energy
• 3)vegetable and fruit group -->vit A&C
• 4)bread and cereal group -->energy, vit,
minerals, protein
Carbohydrates
• source of calories (energy), glucose
important in energy-producing cycles
within cells. RDA
Proteins• enzymes to catalyze the body's chemical
reactions, hormones, muscle, connective
tissue
Fats (& oils)• concentrated source of energy RDA
Vitamins-
Minerals:
• Calcium- blood, cells, body fluids, bones (its
absorption is enhanced by vit D) Magnesiummaintains the electric potential across nerve-andmuscle-cell membranes
• Phosphorus- bones & teeth
• Iodine- essential for functioning of thyroid gland
• Iron- hemoglobin, enzymes
• Zinc- part of important enzymes in the body
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
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
C.2 Proteins
20 different types
R
amino
NH2
Ca
acid
COOH
H
R1
NH2 Ca COOH
H
R2
NH2 Ca COOH
R1
NH2
Ca
H
R2
CO NH
Ca
H
H
Amino acid
Polypeptide
Protein
COOH
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)
Amino Acid
Structure


All amino acids have this general structure.
All amino acids have an amino group, a carboxyl
group and a side chain.
The amino
group is the
nitrogen
atom and
the attached
hydrogen
atoms.
H
H
N
H
C
R
O
C
O
H
R stands for a side chain that can contain
different combinations of carbon, hydrogen,
oxygen, and nitrogen or sulfur.
A carboxyl
group
contains
these parts:
a carbon
atom, an
oxygen atom
and a
hydroxyl
group (O-H).
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
Dehydration Synthesis
• Let’s see how amino acids combine to make
proteins.
• Amino acids combine in the presence of an
enzyme during dehydration synthesis.
H
N
H
C
R
H
O
H
N
C
O
H
H2O
H
O
H
C
R
C
O
H
Dehydration Synthesis
H
N
H
H
O
H
H
C
C
N
C
R
R
H2O
O
C
O
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.
H
C.2.4 PROTEIN STRUCTURE:
-PRIMARY:
• 20 different amino acids: many combinations
• amino acids arranged in linear order
PROTEIN STRUCTURE: SECONDARY:
• -alpha helix:coil 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.
Alpha Helix
Secondary Structure- b Sheet
Oxygen
Nitrogen
Hydrogen
Carbonyl C
Carbon a
R Group
H Bond
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 + Rgroups
• 3) Disulfide bonds
• 4) Hydrophobic interactions- non polar R-groups
tend to stay close together because repelled polar
substances surrounding proteins.
PROTEIN
STRUCTURE:QUATERNARY
• : more than one polypeptide chain join to
form a protein--several folded chains
joined by disulfide bonds (eg. hemoglobin)
Quaternary Structure
The classic example- hemoglobin a2-b2
B/T- Figure 3.7
END OF PART 1
Disulfide Bonding
V/V/P- Figure 16.6
Protein Separations
Paper Chromatography
Electrophoresis
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…
Amino Acid Experiment
1
2
3
4
• 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.
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!
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.
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.
C.2.5 FUNCTIONS:
•
•
•
•
-structure, eg collagen (fibrous proteins)
-biological catalysts (eg. enzymes)
-transport eg. hemoglobin
-energy source
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
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)
Collagen: A Fibrous Protein
Triple Helix
Stabilizing
Inter-strand
H-bonds
Gly-Pro-Pro Repeat
V/V/P- Figures 6.17/18
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)
C.3 Carbohydrates
•
•
Contain the elements Carbon Hydrogen
& Oxygen
There are 3 types:
 Monosaccharides
 Disaccharides
 Polysaccharides
C.3.1 MONOSACCHARIDES:
• -all sugars that contain a single
carbohydrate unit, with an empirical
formula: CH2O
• -contain a carbolyl group (C=O), and at
least two hydroxyl groups (-OH)
• -eg. -glucose, fructose, galactose
Monosacharides
• If n=3, triose (glyceraldehyde)
• If n=5, pentose (fructose, ribose)
• If n=6, hexose (glucose, galactose)
• Used for Energy and Building Blocks
C.3.2 GLUCOSE:
• -C6H12O6
• -a main source of energy
• -contains six carbons with an aldehyde group (HC=O) 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
Isomerism
• They can exist as isomers:
a & b glucose
a
OH
OH
b
Disaccharides
• Formed from two monosaccharides
• Joined by a glycosidic bond
• A condensation reaction:
– glucose + glucose  maltose
– glucose + galactose  lactose
– glucose + fructose  sucrose
C 3.3 Condensation reaction
C
C
C
O
C
C
C
C
C
C
O
OH
OH
C
C
C
Condensation reaction
C
C
C
O
C
C
C
C
C
C
O
OH
OH
C
C
C
Condensation reaction
C
C
C
O
C
C
C
C
C
C
O
O
H2O
C
C
C
Condensation reaction
C
C
C
O
C
C1
C
C
C
O
4C
O
C
C
A disaccharide
1,4 glycosidic bond
C
Polysaccharides
• Polymers formed from many
monosaccharides
• Three important examples:
– Starch
– Glycogen
– Cellulose
Starch
• Amylose
• Amylopectin
a-glucose
1,4 glycosidic bonds
Spiral structure
a-glucose
1,4 and some 1,6
glycosidic bonds
Branched structure
Glycogen
• Insoluble compact
store of glucose in
animals
• a-glucose units
• 1,4 and 1,6 glycosidic
bonds
• Branched structure
Cellulose
•
•
•
•
Structural polysaccharide in plants
b-glucose
1,4 glycosidic bonds
H-bonds link adjacent chains
O
O
O
O
O
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)
• -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)
C.4 Fats
C.4.1 COMPOSITION OF
FATS/OILS:
• -fatty acids: long chain of carbon and hydrogen atoms
with a carbonyl group at the end (C=O)
• -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
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
Unsaturated Fatty Acids
8
CH3
7
CH2
6
CH2
5
CH2
4
CH2
O
3
2
1
CH2 CH2 C OH
3 - Octenoic Acid
8
7
CH3 CH2
O
5
3
4
6
2
1
CH2 CH2 CH2 CH2 CH2 C OH
3, 6 - Octadienoic Acid
Saturated Fatty Acids
8
7
CH3 CH2
O
5
3
4
6
2
1
CH2 CH2 CH2 CH2 CH2 C OH
Octanoic Acid
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 doublebond location--every molecule of I2 used
indicates one double bond.Electrophillic addition
R-C=C-R + I2 ---> R-I-C-C-I-R
• -When the reaction occurs, the iodine will
become clear.
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.
Iodine Value Determination
CH
CH
CH
Cl
+ ICl
Iodine chloride
CH
I
Excess unreacted ICl
ICl
I2 +
+
KI
2 Na2 S2 O3
KCl
+
Na2 S4 O6
I2
+ 2 NaI
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.
Saponification
Saponification - hydrolysis of ester under alkaline
condition.
O
H 2C O
HC
C R
O
O
C R
O
H 2C O
C R
H 2C OH
O
+
3 NaOH
HC
OH
H 2C OH
+
3R C
O Na+
C.4.5 FUNTIONS:
• -Energy source (self-explanatory)
• -Insulation (ditto)
• -Cell membrane-made up of phospholipids
Function of Lipids
•
•
•
•
•
Formation of protective structures
Metabolic reserve
Structural component of cell organelles
Hormones and signal compounds
Vitamins
C.5 Vitamins
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-->vitamins function
as coenzymes (mainly water soluble vitamins)
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
Functions: (structures listed in
data-booklet)
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--nightblindness, xerophthalmia
(tear glands cease to
function)
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)
Vitamin D (calciferol)
CH3
H3C
H3C
H
HO
H
CH2
CH3
CH3
• 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)
Vitamin E
R1
R2
HO
R3
CH3
CH
3
O
(CH2 CH2 CH2 CH2 )2 CH2 CH2CH2 CH(CH 3 )2
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
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.
C.6.1 Production/Roles:
• -ADRENALIN synthesized from amino acid
Tyrosine:when 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.
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.
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.
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.
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.
Sterols
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
Steroid Hormone
Structures
Cortisol
Testosterone
CH3
CH3
HO
cholesterol
Progesterone
Cholic acid
Estradiol
Deoxycholic acid
Cholesterol
CH3
CH3
HO
Sexual Development
estradiol
testosterone
•Key lipid found in cell membranes
•Precursor to steroid hormones:
Metabolic Regulation
glucocorticoids
Digestion
Bile Acids
Pregnancy
progesterone
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.
C.6.4 Steroid Use and Abuse: