Download slib Human Biochemistry

Human Biochemistry
Energy [484-486]
Energy in food is determined using calorimetry
• Exercise 1 page 486
Functions of proteins [486]
1)
2)
3)
4)
5)
6)
7)
Structural
Biological catalysts
Hormones
Protection
Transport
Storage
lubrication
Structure of Proteins [487]
• Proteins are polymers of amino acids
• General structure of amino acids
• 20 naturally occurring
• Called 2-amino acids (or  amino acid)
Structure of Proteins [488]
• Amino acids are both acidic and basic
Structure of Proteins [488]
• Amino acids in the body exist as zwitter ions
• Have high melting points, water soluble, act as
buffers
Structure of Proteins [489]
• At the isoelectric point:
– amino acids have no net charge
– will not move in an electric field and are least
soluble
• Isoelectric point depends on R group
Structure of Proteins [489]
Reactions of amino acids [490]
• Amino acids undergo condensation reactions
Structure of Proteins [490-495]
• Proteins are actually polypeptides
• Proteins have primary, secondary, tertiary, and
quaternary structure
Structure of Proteins [490-495]
• Primary structure is amino acid sequence
• Secondary structure refers to folding of
protein chain
– H-bonds form between amino acids
– -helix and  pleated sheets
Structure of Proteins [490-495]
• Tertiary structure refers to twisting, folding, and
coiling of protein chain due to interactions
between R groups
– Compact structure known as conformation
– Most stable
– H-bonds
– Hydrophobic interactions
– Ionic bond
between R groups
– Disulfide bridge
Structure of Proteins [490-495]
• Quaternary structure is association between
protein chains
Analysis of Proteins [495-497]
How are proteins analyzed?
• First protein is broken down into amino acids
– Hydrolysis reaction using enzyme or heat/acid
– Amino acid sequence will not be known
– Amino acids separated and analyzed by
1)electrophoresis or 2)chromatography
Electrophoresis of Proteins [497]
– Separation based on movement of amino acids in
an electric field (charged)
– Amino acids stop moving at isoelectric point
– Detected by stain or UV light
Electrophoresis of Proteins [497]
– electrophoresis of amino acids
49
Chromatography of Proteins [496]
• Chromatography
– Separation based on solubility differences
between mobile phase and stationary phase
– Amino acid spots become visible with ninhydrin
Exercises 2,3,4 page 497
Carbohydrates [498]
• Functions of carbohydrates in humans
1) Energy source (glucose, fructose)
2) Energy reserve (glycogen)
3) Precursor of other biologically important
molecules (fats, amino acids, nucleic acids)
In plants carbs have a structural function
(cellulose)
Structure of Carbohydrates [498-501]
• types of carbohydrates
1) Monosaccharides (simple sugars)
2) Disaccharides
3) Polysaccharides
Monosaccharide Structure [498-499]
• Classified by number of carbons
– eg: pentose sugar has 5 C
• Essential features are 2 or more OH groups
and a C=O, empirical formula = CH2O
• Monosaccharides can be in chain or ring form
Straight chain monosaccharides [498]
Ring monosaccharides [498 -499]
Disaccharides [499]
• two monosaccharides reaction via a
condensation reaction
– Glycosidic link
• Examples are
– Lactose (milk) -glucose + -galactose
– Maltose (starch digestion) -glucose + -glucose
– Sucrose (cane sugar) -glucose + -fructose
Disaccharide Structure [499]
Polysaccharides [499-501]
• Polysaccharides are polymers of
monosaccharides
• Examples
– Starch (plant carb storage)
– Glycogen (animal carb storage)
– Cellulose (plant structure)
Starch [500]
• Starch
– Polymer of -glucose
– Mixture of two polysaccharides
• Amylose – straight chain 1,4 link of -glucose
• Amylopectin – branched chain 1,4 and 1,6 links of
-glucose
Glycogen [500]
• Glycogen (animal carb storage)
similar to amylopectin with more 1,6 links
Cellulose [500]
• Cellulose (plant structure) 1,4 link of -glucose
Digestion of polysaccharides [501]
– Insoluble in water so must be broken down into
monosaccharides for transportation in blood
– Humans have enzymes to break down starch and
glycogen, not cellulose
– No enzyme for  linkage, although some bacteria
in gut have, cellulose mostly passed through
undigested
– Cellulose is main bulk in waste
Digestion of polysaccharides [501]
• Dietary fiber is the undigested substances
• Benefits
– Aids movement of undigested food
– Prevents constipation, hemorrhoids, irritable
bowel syndrome, colorectal cancer
Lipids [502-509]
3 main types of lipids
1) Triglycerides
2) Phospholipids
3) steroids
Function of lipids [502-503]
1) Energy source
•
More energy than carbs, lipids less oxidized
2) Protection of organs and insulation
•
Adipose tissue
3) Component of hormones and bile
4) Cell membranes
Function of lipids [502-503]
Negative effects of lipids
1) obesity
2) increased risk of heart disease
Main culprit in heart disease is cholesterol
Cholesterol [503]
• Cholesterol is not soluble in blood,
transported in body bound to lipoproteins
– Low density lipoprotein (LDL)
• “Bad cholesterol”
• Increased artery build up
• Saturated and trans fat
– High density lipoprotein (HDL)
• “good cholesterol”
• Protection against heart attack
• Thought to carry cholesterol away from arteries
Types of Lipids
1) Triglycerides
2) Phospholipids
3) steroids
Triglycerides [504-508]
• Major component of fats and oil
• Formed by condensation reaction between
glycerol and 3 fatty acids
Triglycerides [504-508]
Fatty Acids [504-508]
• Most fatty acids have even number of carbons
• Number is between 14 and 22
• Fatty acids can be saturated, monounsaturated, or polyunsaturated
• Saturated are solids at RT, known as fats,
increase LDL
• Unsaturated fats are liquids at RT, known as
oils
Fatty Acids [504-508]
Fatty Acids [504-508]
• Essential fatty acids
– Our body cannot synthesize all the fatty acids we
need, we must get these from our food
– Linoleic acid (omega-6-fatty acid)
– Linolenic acid (omega-3-fatty acid)
– Lower LDL
– Prostaglandins synthesized from essential fatty
acids, prostaglandins lower blood pressure
Fatty Acids and Iodine Number
[504-508]
• Degree of unsaturation of a fatty acid can be
determined using iodine
• Iodine number is the number of grams of
iodine that react with 100 g of fat
• Exercise 6 page 509
Fatty Acids [504-508]
• Food industry uses hydrogenation to produce
saturated fats in foods
– High melting point
– More convenient to store and transport
– More stable
• Process produces trans fats
Fatty Acids [504-508]
lipids - Triglycerides
Digestion of triglycerides [508]
• Fats must be broken down into glycerol and
fatty acids to be transported in blood
• Fats undergo hydrolysis using enzymes
– Lipases
• Slow process
Phospholipids [508]
• Glycerol + 2 fatty acids + a phosphate group
and one of several nitrogen-containing
molecules.
• Polar head and hydrophobic tail
• Phospholipid bilayer makes up cell membrane
Phospholipids [508]
Phospholipids [508]
Steroids [509]
• have a structure of 17 carbon atoms arranged
in four rings
• Cholesterol used in synthesis of other steroids
such as testosterone, estrogen
Steroids [509]
Micronutrients and Macronutrients
[509-513]
• Nutrients – molecules required in diet for
absorption and use by the body
• Micronutrients are needed in extremely small
amounts, mainly function as co-factors of
enzymes (less than 0.005% of body mass)
– mg or mg
– Examples are vitamin B, and the minerals Fe, Cu, F,
Zn, I, Se, Mn Mo, Cr, Co
Micronutrients and Macronutrients
[509-513]
• Macronutrients are needed in relatively large
quantities, used to provide energy and to
build and maintain structure
– Carbohydrates, proteins, lipids
– Na, Mg, K, Ca, P, S, Cl
Micronutrients and Macronutrients
[509-513]
• Vitamins are organic compounds needed for
growth and metabolism that must be taken in
the diet (not made in body)
• Either water or fat soluble (not both)
• Water soluble transported directly in blood
and excess passed through kidneys
– Vitamins B and C
Micronutrients and Macronutrients
[509-513]
• Fat soluble slowly absorbed and excess build
up in fat tissues
– Can cause serious side effects
– Vitamins A, D, E, and K
Micronutrients and Macronutrients
[509-513]
• Solubility depends on structure
• Compare structures of retinol (vitamin A),
ascorbic acid (vitamin C), and calciferol
(vitamin D)
Micronutrients and Macronutrients
[509-513]
• Malnutrition is the lack of nutrients in the diet
– Poor, underdeveloped countries
– Consumption of processed, energy dense, but
nutrient poor foods
– Lack of distribution of global resources
– Depletion of soil nutrients
– Lack of education
– Use of chemicals in food production
Micronutrients and Macronutrients
[509-513]
• The World Health Organization has identified
iodine, vitamin A, and iron as the most
important microdefiencies globally
Macronutrient and disease
• Protein – marasmus and kwashiorkor
Micronutrients and Macronutrients
[509-513]
Micronutrient and disease
• Iron – anemia
• Iodine – goiter
• Retinol – xerophthalmia, night blindness
• Niacin – pellagra
• Thiamin – beriberi
• Ascorbic acid – scurvy
• Calciferol - rickets
Micronutrients and Macronutrients
• Solutions to malnutrition
– Fresh and nutrient rich food rations
– Adding nutrients to common foods
– Genetic modification of food
– Nutritional supplements
– Increased nutritional information on foods
– education
Hormones [513-516]
• Hormones are chemical messengers
• Secreted directed into the blood by endocrine
glands and act on target cell
– Target cells have specific receptors for hormone
• Important hormone/endocrine gland/target
cell are shown on page 514
• Compare and contrast structures of
cholesterol and sex hormones
oral contraceptives [515]
• Mode of action of oral contraceptives
– Prevent ovulation
– Pills contain progesterone and estrogen that
suppress secretion of follicle stimulating hormone
and luteinizing hormone which trigger ovulation
– Simulates hormonal conditions during pregnancy
– Pill taken for 3 weeks with 1 week off
– Prescription only
– Morning after pill
Steroids [516]
• Use and abuse of steroids
• Female hormones
– Oral contraceptive use steroids
– Hormone replacement therapy use steroids
Steroids [516]
• Male steroids are called androgens
– Testosterone is used in treatment of testes and
breast disorders
– aka anabolic steroids which promote tissue
growth, especially muscle
– Used to gain weight after debilitating disease
– Abused by athletes
• Side effects include infertility, liver damage, sexual
characteristics