Marks’ Biochemistry
Chapter 1 – Metabolic Fuels
Review
Triglycerides
Β-oxidation
Glycolysis
Cells require ATP for normal function
of everyday processes, including
biosynthetic reactions, muscle contraction,
active transport.
Proteins
Starch and glycogen are both homopolymers of only glucose, the predominant sugar
in the blood.
Sucrose and Lactose are both
disaccharides while fructose,
glucose, and galactose are all
monosaccharides.
Lactose
The proteins – made from 20 different amino acids
Composed of the amide or peptide bond.
Proteins are heteropolymers of different AAs
Composed primarily of C, H, O, and N, having 16% N by weight.
Metabolize for energy
Or build own proteins
Fats – Dietary fat composed of Triacylglycerols (aka triglycerides) which consist
Of 3 fatty acids esterified to a glycerol molecule
Storage fat
3-carbon
backbone
used in
gluconeogenesis
Fatty acids
To be metabolized
by β-oxidation
to yield ketone
bodies
Our friend, ethanol (EtOH)
Also considered part of dietary intake,
more than proteins and carbohydrates
(next slide)
Table 1.1 Caloric
Content of Fuels
kcal/g
Carbohydrate
4
Fat
9
Fats contain much less O/H2O = more reduced, yield more energy
when oxidized!
Protein
4
Oxidation of proteins to CO2, H2O, NH4+
Alcohol
7
Even our friend EtOH yields more than protein and carbs
Carbs contain significant amounts of oxygen = partially oxidized
Bottom line: must know this slide!
Liver glycogen
0.08kg (0.2%)
(Fuel storage b/w meals)
Protein
6kg (14.5%)
(Has many functions)
Muscle glycogen
0.15kg (0.4%)
(Muscle glycogen for
muscle contraction only)
Fat
15kg (85%)
(Only contains
15% water!)
A 70kg man after an overnight fast will yield this in fuel consumption
18kg fat = 34kg glycogen + 136kg H2O = 170kg man
Daily Energy Expenditure = Resting Metabolic Rate + Diet-induced Thermogenesis
i.e. DEE = RMR + DIT
RMR, the energy required to maintain life functions (differs from BMR very little)
Basal metabolic rate (BMR) expressed in kcal/day: affected by size, age, sex, other factors
(think metabolically active tissue)
↓ for women (more inactive adipose tissue), ↑ for men
Temperature affects BMR
HYPERthyroidism = excessive thyroid hormone > more heat, i.e. BMR ↑
HYPOthyroidism = insufficient thyroid hormone > less heat, i.e. BMR ↓
Children/pregnant women are growing, so BMR ↑
Aging people are not so active, so BMR ↓
BMR – assume 24kcal/day/kg body weight
Sedentary
Uses only 30% RMR/day
Physical exercise
Can use 60% to 70% RMR/day with about
two hours of moderate exercise
100% with several hours of exercise
Medical student
I CAN SEE THIS BEING ASKED
ON THE TEST!!!!
BMI = weight (kg) =
[height (m)]²
Underweight is below 18.5
Average is 20-25
Ideal is 18.5-24.9
Obese is over 30
704 x weight (lb)
[height (in)] ²
Table 1.4
Equations for
Predicting Basal
Metabolic Rate
(BMR) From Body
Weight (W) in
Kilograms
Males
Females
Age Range (y)
0–3
BMR (kcal/d)
60.9W - 54
Age Range (y)
0–3
BMR (kcal/d)
61.0W - 51
3–10
22.7W + 495
3–10
22.5W + 499
10–18
17.5W + 651
10–18
12.2W + 746
18–30
15.3W + 679
18–30
14.7W + 496
30–60
11.6W + 879
30–60
8.7W + 829
>60
13.5W + 487
>60
10.5W + 596
Source: Energy and protein requirements: report of a Joint FAO/WHO/UNU Expert Consultation.
Technical report series no. 724. Geneva: World Health Organization; 1987:71.
See also Schofield WN. Hum Nutr Clin Nutr. 1985;39(suppl).
FACTORS AFFECTING BMR, a recap!
•Gender (males > females)
•Body temperature (> w/fever)
•Environmental temperature (>in cold)
•Thyroid status (>in hyperthyroidism)
•Pregnancy/lactation (>)
•Age (>in childhood)
•Diet-induced Thermogenesis – energy lost as heat due to the energy
needed for digestion is about 10% of calories taken in
•Adipose mass generally does not contribute to BMR
and therefore calculations for obese individuals are not accurate
(also a person who is very muscular may be classified as obese when
they are not)
Daily Energy Expenditure (DEE) = BMR + physical activity
For student/no exercise
= 72.9(1*8 + 1.5*16) = 2327kcal/day
+1 hr moderate exercise
= 72.9(1*8 + 1.5*15 + 1*5)+ = 2588kcal/day
(1750kcal/day/24hrs = 72.9kcal/hr)
Table 1.5 Typical Activities With Corresponding Hourly Activity Factors
Activity Category
Resting: sleeping, reclining
Hourly Activity Factor (for Time in Activity)
1.0
Very light: seated and standing activities, driving, laboratory work, keyboarding,
sewing, ironing, cooking, playing cards, playing a musical instrument
1.5
Light: walking on a level surface at 2.5 to 3 mph, garage work, electrical trades,
carpentry, restaurant trades, house cleaning, golf, sailing, table tennis
2.5
Moderate: walking 3.5 to 4 mph, weeding and hoeing, carrying loads, cycling,
skiing, tennis, dancing
5.0
Heavy: walking uphill with a load, tree felling, heavy manual digging, mountain
climbing, basketball, football, soccer
7.0
The hourly activity factor is multiplied by the basal metabolic rate, BMR (resting metabolic rate, RMR) per hour times the number of
hours engaged in the activity to give the caloric expenditure for that activity. If this is done for all of the hours in a day, the sum over 24
hours will approximately equal the daily energy expenditure.
Source: Reprinted with permission from Recommended Dietary Allowances. 10th ed. Washington, DC: National Academy Press; 1989.
FYE = for your entertainment/education
•Breakfast – breakfast sandwhich & 12oz orange juice
•(muffin/sausage/egg/cheese
27x9= 243
•27g fat =
30x4= 120
•30g carbs =
•21g protein = 21x4= 84
447
•
Total=
•Orange juice
•33g carbs = 33x4= 132
8
•2g protein = 2x4=
140
•
Total =
•Lunch – large cheeseburger, large fries & 32oz cola
•510kcal + 570kcal + 310kcal = 1390
•Dinner – chicken sandwich, salad, water
•660kcal + 400kcal + 0kcal = 1060
•Late night snack – one 1.55oz chocolate bar
•230kcal
•Grand total = 3267kcal/day
Nota bene:
One hour on
the bike
=200kcal!!!
The moral of the story IS:
Calories in=3267
Calories out=2588
If all this goes to fat
679kcal/9kcal/g
=75.4g = 0.0754kg = 0.165lbs
Difference= +679kcal/day
Pounds per year
0.165lbs x 365days
= 60.5lbs/yr weight gain!!
Calories in=2167
Calories out=2588
Difference= -412kcal/day
If all this is removed from fat
412kcal/9kcal/g
=46.78g = 0.04678kg = 0.103lbs
Pounds per year
0.103lbs x 365days
= ~40lbs/yr weight loss!!
What we need:
•Carbohydrates – elimination causes health problems; low-carb must have high-fat = obesity
•Essential fatty acids – saturated are NON-essential (we make them ourselves)
We require unsaturated FA
•Linoleic acid, ω-6 from plants
•Linolenic acid, ω-3 from plants
•Eicosapentaenoic acid, ω-3 from fish oil
•Docosahexaenoic acid, another ω-3 from fish oil
Needed for making membranes and some hormones (eicosanoids)
Protein
•Essential amino acids = Arg, His, Iso, Leu, Lys, Met, Phe, Thr, Try, Val
vs
NON-essential AA = Ala, Asn, Asp, Cys, Gln, Glu, Gly, Pro, Ser, Tyr
Conditional Essential AA
Histadine needed very small in adults – efficient recycling
Histadine needed MORE in growing children/pregnant women
Tyrosine, from Phenylalanine; need Tyr if Phe is inadequate (or phenylketonuria PKU)
Cysteine, using Sulfur from Methionine, required under certain conditions
Edema and Dermatosis from Kwashiorkor
Protein deficiency
HYPOalbuminemia, anemia, edema,
Pot belly, loss of hair, other tissue injury
Murasmus
Prolonged calorie and
Protein malnutrition
Do NOT develop edema
Table 1.6 Nitrogen Balance
Positive nitrogen balance
Growth (e.g., childhood,
pregnancy)
Dietary N > excreted N
Nitrogen balance
Normal healthy adult
Dietary N = excreted N
Negative nitrogen balance
Dietary deficiency of total
protein or amino acids:
catabolic stress
Dietary N < excreted N
Water soluble vitamins:
Vitamin C
Thiamin
Riboflavin
Niacin
Vitamin B6 (pyridoxine)
Folate
Vitamin B12
Biotin B7
Pantothenic acid B5
Choline
Fat soluble vitamins:
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Just remember ADEK
For fat soluble vitamins
Most vitamins are used for synthesis of coenzymes that
assist enzymes in catalyzing biochemical reactions
Vitamin C – Ascorbic acid
Deficiency causes
-Scurvy
Find in citrus fruits, potatoes, peppers, broccoli,
spinach, strawberries
Needed for collagen formation
Thiamine – B1
Deficiency causes
-Beriberi
edema, heart failure
-Wernicke-Korsokoff (not in book)
EtOH induced, brain damage (dementia)
Find in cereal grains, beans, nuts, milk, brewer’s yeast
Needed for decarboxylation reactions
Beriberi
Riboflavin – B2
Deficiency causes
-Ariboflavinosis
-dermatitis
-glossitis
Find in milk, meat, wheat, green veggies,
fish
Needed for FADH2 synthesis
dermatitis
glossitis
Niacin – B3
Deficiency causes
-Pellagra
Find in meat, enriched cereals or whole grains,
most foods
Needed for NADH synthesis
Pellagra
desquamation, erythema,
scaling, and keratosis of
sun-exposed areas
Pantothenic acid – B5
Deficiency causes
-irritability/reslessness
-fatigue
-apathy/malaise
-gastrointestinal disturbances
-neurologic symptoms
Find in liver, eggs, yeast, milk
Needed for CoA formation
Pyridoxine – B6
Deficiency causes
-seborrheic dermatitis
-microcytic anemia
-depression
-confusion
-convulsions in infants
Find in eggs, liver, yeast, peas, beans, milk
Needed for amino acid de-/trans-aminations
Seborrheic
dermatitis
Infant convulsions
Biotin – B7
Deficiency causes
-conjunctivitis
-CNS abnormalities
-glossitis
-alopecia (balding)
-dry, scaly dermatitis
Find in beef liver, yeast, peanuts, chocolate, eggs
Needed for carboxylation, fat synthesis
alopecia
Folic acid – B9
Deficiency causes
-megaloblastic anemia
-impaired cell division/growth
-NTD
Find in citrus fruits, dark green veggies, cereals/breads,
legumes
Needed for carbon transfers – in making purines
Vitamin B12
Deficiency causes
-megaloblastic anemia
-neurologic symptoms (dementia)
Find in animal products
vegetarians beware!!!
Needed for fat/AA metabolism
Choline
Deficiency causes
-liver damage
Find in milk, liver, eggs, peanuts
Needed for structural integrity, signaling pathways
Vitamin A (betacarotine)
Deficiency causes
-night blindness
-xerophthalmia
Find in carrots, broccoli, squash,
Sweet potoatoes, leafy veggies,
Liver, eggs, butter, fish, cheese
Needed for photodetection
Xerophthalmia
Night blindness
Vitamin D - calciferol
Deficiency causes
-Rickets (in children)
-osteomalacia
Find in milk, exposure of skin to sunlight
Needed for calcium absorption
Vitamin E – α-tocopherol
Deficiency causes
-muscular dystrophy
-neurologic abnormalities
Find in vegetable oils, wheat germ, nuts, green leafy veggies
Needed for antioxidant activity (free radical scavenging)
Vitamin K - phylloquinone
Deficiency causes
-defective blood coagulation
-hemorrhagic anemia of newborn
Find in green leafy veggies, cabbages, bacterial flora of intestine
Needed for carbon transfers
Excessive intake of vitamins cause deleterious effects
Hypervitaminosis A – desquamation of skin, birth defects
Hypervitaminosis C – diarrhea, GI disturbances
Intake normally above when taken in single vitamins, not from
foods
Minerals are also required in the diet
Table 1.8 Minerals
Required in the Diet
Electrolytes
Sodium
Minerals
Calcium
Trace Minerals
Iodine
Ultratrace or Trace
Minerals a
Manganese
Potassium
Phosphorus
Selenium
Fluoride
Chloride
Magnesium
Copper
Chromium
Iron
Zinc
Sulfur
Molybdenum
aThese
minerals are
classified as trace or as
ultratrace.
Fluoride Deficiency
High fluoride
Causes Fluoride mottling
Building, changes color, brittle
Just enough fluoride
Can give you a great
Smile!! =D
Iron Deficiency
Iron is needed for the oxygen-carrying
component in hemoglobin (heme group)
glossitis
Spoon nailing
Zinc Deficiency
Psoriasiform lesion
of Zn deficiency
hair is very thin and sparse
after treatment
Iodine deficiency
Calcium deficiency – osteoporosis = elderly women
Phosphorous deficiency – bone loss, weakness, anorexia, malaise, pain