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Biology 105: Biology: Science for Life with Physiology, 3rd Ed., Belk & Maier
Chapter 3: Diet: Cells and Metabolism, pp 53-79, with backup from Chapter 2, etc…
Nutrients (pp 54-61)
I. Substances providing structural materials or energy
A. Macronutrients
1. Required in large amounts
2. Water
a. Life ceases within a few days without water
b. helps body dissolve & disperse other nutrients
i. facilitates biochemical reactions
c. dissolves & eliminates metabolic waste products
d. maintains blood pressure
e. maintains cells’ osmotic pressure
f. regulates body temperature
3. Carbohydrates
a. basic CH2O formula
b. major source of energy, 4 Calories per gram
c. source of structural materials in cells
i. monosaccharide = glucose, fructose, ribose, galactose, etc…
ii. disaccharide = sucrose, lactose, maltose, etc…
iii. polysaccharide cellulose in cell wall
iv. polysaccharide chitin in exoskeletons of insects, spiders, & lobsters
v. polysaccharide chains of glycogen, starch & dextran = stores of glucose units
d. Complex carbohydrates are found in fruits, vegetables, beans, & grains.
i. Dietary fiber (roughage) is indigestible complex carbohydrates but good
because it helps keep good cholesterol levels & may reduce risk of cancers.
4. Proteins
COOa. made of amino acids: 20+ (R-CH-NH3+; R= side chain/ specific properties)
i. essential ones = PVT TIM HALL: phenylalanine, valine, threonine,
tryptophan, isoleucine, methionine, histidine, alanine, lysine, leucine
{Alanine can be made by your body, so it’s not really “essential”.}
ii. Many amino acids can be made from intermediates of major pathways
like the citric acid cycle.
b. amino acids linked via peptide bond  dipeptides polypeptides  proteins
i. requires input of free energy
ii. –COO- end of 1 amino acid reacts with the +H3N- end of another 
+
H3N-CHR-CO-NH-CHR2-COO- + H2O {peptide bond in italics}
iii. Convention has the polypeptide written beginning at the amino end.
c. comprise ½ the dry weight of most cells
i. integral to plasma membrane & other structures
ii. serve as catalysts (enzymes), membrane channels, hormonal messages
d. Structures
i. primary structure = amino acid sequence <determined from DNA>
ii. secondary structure = spatial arrangement of amino acid residues nearby
( helix,  pleated sheet, & collagen helix are common kinds.)
iii. tertiary structure = spatial arrangement of amino acids far apart linearly
iv. quaternary structure = spatial arrangement of subunits
v. domains = compact globular units with specific properties/ functions
e. found in beef, poultry, fish, beans, eggs, nuts, milk, yogurt, & cheese
f. Although some plants may lack some essential amino acids, vegetarians with a wide
of plants in their diet can rely on amino acid complementation for protein synthesis.
g. As a fuel source, proteins provide 4 Calories per gram.
5. Lipids
a. partially/ entirely hydrophobic organic molecules composed of hydrocarbons (-CH2-)n
b. include fats, phospholipids, and sterols
c. Fats = a 3-carbon glycerol molecule with 3 long fatty acid chains attached
i. Fatty acids with no double bonds are “saturated” & are solids at room temp.
ii. Fats with H’s bound on same side of C-C double bond are in cis configuration
iii. Trans fats are not required or beneficial; bad for heart, arteries, & diabetes
iv. provide 9 Calories per gram of energy when metabolized
v. found in milk, cheese, meat, nuts, & vegetable oils
vi. Fat, stored just below the skin, acts as insulation.
d. Phospholipids = a 3-C glycerol molecule with 2 long fatty acid chains as tails and 1
phosphate head group with polar/ hydrophilic properties
e. Steroids = 4 fused C-containing rings; includes cholesterol & sex hormones
*** Nucleic acids are NOT a macronutrient but are 1 of the 4 macromolecules for Life.
a. DNA = deoxyribonucleic acid – primary storage of genetic information
i. double stranded -helix
ii. James Watson & Francis Crick won Noble prize for finding its structure.
iii. Rosalind Franklin, Maurice Wilkins & Linus Pauling (-helix) contributed.
b. RNA = ribonucleic acid – key in synthesis of proteins
i. single stranded
c. covalently bound long strings of nucleotides (sugar + phosphate + nitrogenous base)
i. The sugar-phosphate bond forms the “backbone” of nucleic acid.
ii. The 2 strands are antiparallel, one proceeding 5’ to 3’and the other 3 ’to 5’
(upside down); 3’ is linked via sugar’s C3’s –OH group, 5’ to C5’s –OH
iii. DNA nitrogenous bases: Adenine, Guanine, Thymine, Cytosine
iv. RNA nitrogenous bases: Adenine, Guanine, Uracil, Cytosine
d. complementary base pairs: purine to pyrimidine (A = T/ A = U; G = C) via H-bonding
i. Purines are double-ring structures, whereas pyrimidines are single-ring bases
ii. “Chargaff’s rules” = base-pairing rules above; help determine DNA structure
B. Micronutrients
1. Needed in very small amounts but NOT for energy.
2. Vitamins function as coenzymes (act with different enzymes to hasten biochemical reactions).
3. Vitamins also aid in absorption of other nutrients.
4. Fat-soluble vitamins = A, D, E, K; others are water-soluble & cannot “build up” to toxic level.
a. Only Vitamin D is synthesized by your body (via sunlight on skin’s cholesterol).
5. Minerals are non-C based, essential substances such as Ca, Cl, Mg, P, K, Na, Fe, S, Se, etc…
a. are water-soluble; are NOT synthesized by your body (therefore are essential)
6. Antioxidants (Vit C, E, & K, -carotene, flavenoids, lutein, lycopene, & Se as a coenzyme)
a. protects against free radicals whose extra electron makes them super-reactive/ harmful
b. hydroxyl radicals, superoxide anion, singlet oxygen, & oxygenate heme intermediates
Enzymes & Metabolism (pp 61-65) with notes from Biochemistry, 3rd Ed, Lubert Stryer, ©1988
I. Enzymes
A. Proteins (& some RNA molecules, L19 RNA) that regulate rate of all metabolic reactions as catalysts
1. Naming of enzymes
a. Substrate is usually the root word with an –ase ending.
i. Lactose’s degradation is catalyzed by lactase, fructose by fructase, etc…
b. Sometimes the action of the enzyme is the root word or –zyme is the suffix.
i. All kinases involve the movement of a given moiety.
ii. Lysozyme (Fleming, 1922) lysed bacteria
iii. Ribozymes = RNA enzymes
c. Historically, discoverers of enzymes named them as they wished.
i. Pepsin, trypsin, chymotrypsin, subtilisin, thrombin, etc…
2. Lower the activation energy of those reactions [Gibbs free energy of activation, G]
a. Use intermolecular forces to orient substrates optimally for breaking/making bonds
b. Act to stabilize reaction intermediates/ transition states
i. Enzyme-substrate complex has a new reaction pathway of lower G.
ii. Selectively determines which one of potential chemical reactions will occur
c. Can couple the reactions of separate binding sites
i. Enzymes then act as molecular switches.
d. “Accelerates reactions by factors of at least a million”
i. E + S ES  E +P , where E= enzyme, S= substrate, P= product
ii. Michaelis-Menten equation for rate of reaction is V = Vmax ([S]/[S] KM)
where KM = (k2 + k3)/ k1 with k1 = forward rxn, k2 reverse rxn, & k3 final rxn
iii. Rate cannot exceed rate of diffusion-controlled encounter of Enz with Sbstrte
e. Induced fit model
i. Enzymes are specific for given substrate due to size & shape of active site,
typically a nonpolar cleft or crevice.
ii. Substrate is bound to enzyme by multiple weak attractions, ing specificity
iii. Enzyme’s structure is changed upon binding of substrate to its active site.
iv. Shape change likewise stresses substrate’s bonds, aiding in their cleavage.
f. Lock and key model
i. Doesn’t account for shape changes that occur upon substrate binding
II. Calories and Metabolic Rate
A. calorie = amount of energy required to raise temperature of 1 gram of H2O 1o Celsius
1. Calorie (with a capital C) = 1000 calories = 1 kilocalorie
B. Food is metabolized and the potential energy of its chemical bonds is released /converted.
1. Speed & efficiency of enzymes determine one’s metabolic rate.
a. Metabolic rate is measure of one’s energy use.
b. Basal metabolic rate (BMR) is for an awake, alert, resting individual.
3. Energy obtained allows one to do all activities, conscious & unconscious.
a. Cells convert food’s energy into ATP in the mitochondrion.
b. Excess energy from metabolism is stored as fat for later use.
4. MR/BMR is influenced by many factors other than diet & activities.
a. age & gender
b. weight & muscle mass
c. genetics
Transport across Membrane, (pp 66-69) with notes from Molecular Biology of the Cell, 2nd Ed., © 1989
I. Plasma membrane construction
A. Phospholipid bilayer with integral & peripheral proteins + cholesterol /sterols
1. Polar phosphate heads face toward the inside & outside of the cell.
a. Polar groups, water, and ions are accepted.
b. Nonpolar, hydrophobic molecules are repelled if unaided by specific proteins.
2. Nonpolar fatty acid chains compose interior of membrane.
a. Three major types of lipids = phospholipids, cholesterol, & glycolipids (amphipathic)
b. Nonpolar, hydrophobic substances pass readily.
c. Polar entities cannot pass through unaided.
3. Together, these layers create a semi-permeable membrane that regulates passage.
a. CO2, H2O, & O2 pass readily through membrane.
b. The concentration of molecules across the membrane is also a determinant.
i. Concentration gradient is formed from area of higher concentration to lower.
B. Fluid mosaic model
1. Membrane is dynamic.
a. Membrane’s lipids and proteins can move laterally within the bilayer.
b. Cholesterol & other sterols help firm up the membrane & prevent its freezing.
II. Types of membrane transport
A. Passive transport (requiring no input of energy by the cell)
1. Diffusion
a. = Movement of particles from area of high concentration to area of low concentration.
b. All atoms vibrate with random motion causing spontaneous mixing of particles.
i. Kinetic-molecular theory of matter applies to all states of matter.
c. Molecules/ substances move along their concentration gradient (from higher to lower)
d. Only very small, hydrophobic molecules cross the membrane by simple diffusion.
2. Facilitated diffusion
a. Hydrophilic substances are transported across the membrane by embedded proteins.
b. Integral proteins act as channels or carriers for movement across membrane.
i. Channel proteins form water-filled pores extending across lipid bilayer.
ii. Carrier proteins bind specific solute,  conformation, flip solute across.
iii. Concentration AND charge of solute create solutes’ electrochemical gradient
c. Carrier proteins act like membrane-bound enzymes with specific binding sites.
i. Some are uniports, moving only 1 solute across.
ii. Others are coupled transporters, moving 1 in conjunction with another solute.
Movement may be in same direction , symport, or opposite direction antiport.
3. Osmosis
a. = Movement of water across a semi-permeable membrane down its conc gradient
b. Water can move through aquaporins, in facilitated diffusion, or by simple diffusion.
B. Active transport (requiring input of energy / ATP by cell)
1. Moves substances against their concentration gradient
2. May involve membrane “pump” proteins powered by ATPase enzyme
3. Endocytosis: movement of large substances via membrane-fusing vesicles into the cell
i. Pinocytosis = transport of solutes or fluids
ii. Phagocytosis = movement of large particles, even cells; fuse with lysosomes once in
4. Exocytosis: movement of large substances via membrane-fusing vesicles out of the cell
Body Fat and Health, (pp 70-75)
I. Evaluating Body Fat
A. Healthy standards
1. Gender
a. women = 22%; essential range is 12% - 32%
i. have an 8% thicker dermis layer than men
b. men = 14%; essential range is 3% - 29%
2. Frame size
a. larger-boned folks carry more fat
3. Former standards were derived from 1950’s life insurance policy owners & are biased.
B. Body Mass Index (BMI)
1. BMI is calculation incorporating height & weight to determine an estimate of body fat
2. Still is not 100% valid for “healthy weight”
a. does not account for gender, frame size, or muscle mass, which is heavier than fat
3. Healthy range = 20-25 BMI
a. Values of > 30 = obesity
C. Health risks with obesity
1. diabetes
a. disorder of carbohydrate metabolism due to lack of (response) to insulin
b. insulin is secreted by the -cells of the islets of Langerhans in the pancreas
i. lowers blood sugar by stimulating muscle cells to store or use its glucose
c. insulin deficiency causes diabetes mellitus so cells starve & blood levels soar
d. excess glucose inhibits renal water reabsorption  dehydration, renal damage,
blindness, cardiovascular disease, amputations, coma, and death
Type I diabetes (insulin-dependent diabetes mellitus, or IDDM)
a. immune cells attack islet cells, killing them
b. treated with daily injections of insulin + islet cell transplant
c. not correlated with obesity
Type II diabetes (non-insulin-dependent diabetes mellitus, or NIDDM)
a. Major type (~ 90%)
b. Used to occur in folks over 40 yrs old, but now becoming more common earlier
c. caused by insufficient insulin production or less responsive target cell receptor
d. can be controlled by diet and exercise
2. Hypertension
a. “high blood pressure”
i. measured as systolic blood pressure over diastolic blood pressure
systolic = pressure exerted by the blood against vessels as heart contracts
diastolic = pressure between contractions of the heart when heart relaxes
ii. dangerous range = persistent 140/ 90 vs. normal = 120/ 80
3. Heart attack
a. sudden interruption of blood supply to the heart due to vascular blockage
b. can cause irreparable damage
4. Stroke
a. sudden loss of brain function due to vascular blockage/ rupture
b. can cause irreparable damage
5. Atherosclerosis
a. deposition of plaque/ cholesterol due to increased damage from high blood pressure
i. fat deposits narrow blood vessels less blood to heart & higher pressures
ii. Low-density lipoprotein (low in protein, high in cholesterol) carry cholesterol
to cells throughout body to help maintain membranes, etc…
ii. High-density lipoproteins (high in protein, low in cholesterol) rounds up
LDLs and returns them to the liver where it’s excreted as bile
b. Ratio of LDL/ HDL = rate of level of leaving body cells & returning to liver
i. Bad news if LDL > 100 or total cholesterol is > 200
ii. Diets high in plant (no cholesterol) & low in saturated fats are good.
iii. Genes may also increase cholesterol production, so meds may be needed.
D. Eating disorders
1. Anorexia
a. self-starvation
b. can cause altered heart rhythms
c. can result in decrease hormone/ estrogen release
i.  amenorrhea (cease menstruation) & possible sterility
ii.  osteoporosis (lower bone density)
2. Bulimia
a. forced purging of food, such as vomiting after (binge) eating
b. can cause all problems above PLUS issues from excess purging
i. increased stomach acid encounters  dental & gum problems
ii. ruptured stomach
iii. dehydration  death
E. Fitness
1. Not just diet, BMI, LDL/ HDL, & numbers
2. Exercise
3. Well-balanced living
a. work
b. play
c. quiet time/ reflection