metabolism

metabolism

refers to all the chemical reactions in the body, provides energy for homeostasis and functions such as breakdown and replacement of cell components, growth and division, secretion, contraction, and action potentials

catabolism

breakdown of organic substances, produces energy(exergonic), captures 40%, 60% lost to heat

anabolism

synthesis of new compounds, requires energy(endergonic)→ repair, growth, secretions, store reserves

ATP(adenosine triphosphate)

energy currency of the cell, short term storage(anabolism-catabolism)

mitochondria

cellular component that provides energy(TCA cycle and electron transport chain)

turns glucose and O2 → CO2, water, energy(ATP)

O2= aerobic

glycolysis (carb metabolism)

break down of glucose(6-carbon) into pyruvate 2(3-carbon), anaerobic, produces 2 ATP and 2 NADH, takes place in the cytosol of cell

step 1 of carb metabolism

 pyruvic acid + coenzyme A → Acetyl-CoA + CO2
& NADH (3-carbon→ 2-carbon) 2(NADH)
 TCA (krebs) Cycle- a reaction sequence or cycle
that yields 2(3-NADH, 1-FADH2, 1GTP1ATP)
 Aerobic, cellular respiration, takes place in the
mitochondria, goes around twice for 1 glucose
molecule

TCA cycle (krebs)

Acetyl CoA + adds a 2-carbon to 4-carbon
Oxaloacetic acid→ Citric acid→ Isocitric acid→ A-Ketoglutaric acid (NADH, CO2)→ Succinyl-CoA (NADH, CO2)→ Succinic acid (GTP→ATP) → Furmaric acid (FADH2)→ Malic acid→ Oxaloacetic acid (NADH)

electron transport system

(oxidative phosphorylation) occurs inside mitochondria, produces over 90% of ATP, tremendous energy( 2 H2 + O2→ 2H2O), cells can not handle explosions, uses enzymes in series of small controlled steps, (sequence of oxidation-reduction reactions)

oxidation

loss of an electron, loss of a hydrogen ion

reduction

gain of an electron, gain of a hydrogen ion

electron transport system steps

• Starts by removing H’s from NADH & FADH2(oxidation)

• NADH --- FMN, FADH2 --- coenzyme Q

• Uses proteins called Cytochromes (protein + metal)

• H’s collect in space between inner and outer mitochondrial membranes, sets up a concentration gradient

• The passing of H’s back through hydrogen ion channels generates ATP (chemiosmosis)

• At the end of the system O2 accepts
  electrons/hydrogen to form water

• If oxidative phosphorylation slows or stops the cell dies

glycolysis energy yield

2 ATP

NADH from glycolysis thru ETS energy yield

4 ATP

each NADH yields 3 ATP

TCA-GTP→ ATP

2 ATP

TCA-NADH thru ETS

24 ATP

TCA-FADH2 thru ETS

4 ATP

each FADH2 yields 2 ATP

what is the total energy yielded

36 ATP or 38 ATP(cardiac and liver cells)

glycogenesis

formation of glycogen from glucose in the liver and skeletal muscles

gluconeogenesis

the synthesis of glucose from non-carbohydrate sources(lactic acids, glycerol, amino acids) pyruvate to acetyl- CoA can not be reversed- turned back into glucose, therefore fatty acids and many amino acids can not be used either-there pathways produce acetyl-CoA

glycogenolysis

breakdown of glycogen into glucose

if O2 is scarce, anaerobic, muscle fibers during exercise, pyruvic acid + 2NADH → lactic acid

*liver converts lactic acid to pyruvate

what is the most abundant lipid in the body?

triglycerides

lipid catabolism(lipolysis)

yields to glycerol and 3 fatty acids

glycerol gets converted to pyruvate and enters TCA cycle

fatty acids generate acetyl-CoA

beta-oxidation

sequence of reactions where fatty acids are broken down into 2-carbon pieces(acetyl-CoA), occurs inside mitochondria-so acetyl CoA can enter TCA cycle, great source of energy, each 2-carbon fragment yields 12 ATP from acetyl-CoA thru TCA cycle + 3 ATP for 1 NADH + 2 ATP for 1 FADH2

• process costs 1 ATP

one 18 carbon fatty acid yields

144 ATP

lipid synthesis(lipogenesis)

synthesis of lipid compounds, most lipids including steroids and nonessential fatty acids begin with acetyl-CoA, since lipogenesis uses acetyl-CoA it can begin with lipids, amino acids or carbs. linoleic acid and linolenic acid are 18-carbon unsaturated fatty acids that can not be made in the body- therefore they are the essential fatty acids

lipid transport

all cells in the body need lipids to make steroid hormones and maintain their cell membranes. because lipids are not soluble in blood(water) they must be transported by proteins(lipoproteins)

free fatty acids

easily diffuse across cell membranes, bound to albumin-(plasma protein), important energy source

chylomicrons

95% triglyceride, largest lipoprotein, carries absorbed lipids from GI tract to blood stream, lipoprotein lipase in muscle, heart adipose, and liver tissue yield→ fatty acids and glycerol

very low density lipoproteins(VLDL)

contain liver made triglycerides, transports these triglycerides to peripheral tissues(triglycerides out)

intermediate density lipoprotein(IDL)

size and composition between VLDL and LDL, contains less triglycerides than VLDL(triglycerides return trip)

low density lipoproteins(LDL)

contains cholesterol and few triglycerides, delivers cholesterol to peripheral tissues, bad cholesterol- dumps cholesterol(cholesterol out)

high density lipoproteins(HDL)

equal amount of protein and cholesterol, transports cholesterol from peripheral tissues back to liver for storage or bile, good cholesterol- picks up cholesterol(cholesterol back)

protein metabolism

the breakdown of protein peptide bonds to amino acids, hundreds of thousands of proteins to just 20 amino acids, the body would prefer to use amino acids for building proteins but can use them for energy in the TCA cycle if it has to

amino acid metabolism

the break down of amino acids, -NH2(amino) is removed by vitamin B6

transamination

attaches an amino group from amino acid to a keto acid(trading)

deamination

removal of amino acid group and an H, generates ammonium- very toxic, liver converts to urea

protein catabolism impractical

1. more difficult to break down,

2. ammonium is toxic,

3. amino acids are important structurally

protein synthesis

20 different amino acids, 10 essential(isoleucine, leucine, lysine, threonine, tryptophan, phenylalanine, valine, methionine, arginine*, histidine*)

*essential for children

amination

attachment of an amino group

liver

contains great diversity of enzymes, can breakdown and synthesize most carbs, lipids, and amino acids needed by cells

adipose tissue

stores lipids as triglycerides

skeletal muscle

almost ½ of a healthy individual’s body weight, maintains glycogen reserves, amino acids

neural tissue

has high demand for energy, must be provides with supply of glucose

other peripheral tissues

do not maintain large metabolic reserves, metabolize glucose and fatty acids

absorptive state

around 4 hour period following a meal, absorption takes place, insulin is the primary hormone

postabsorptive state

nutrient absorption is not happening, must rely on internal energy reserves, glucagon, epinephrine, glucocorticoids are key hormones, liver cells try to conserve glucose- breaks down lipids and amino acids to generate acetyl-CoA, as acetyl-CoA levels rise ketone bodies form

ketone bodies

3 types- acetoacetate, acetone, beta-hydroxybutyrate

peripheral tissues reconvert ketone bodies back into acetyl-CoA for TCA cycle, high levels of ketone bodies seen in starvation- pH begins to fall in the blood and can lead to ketoacidosis which can disrupt tissue function

diet and nutrition

absorption of nutrients from food is call nutrition

balanced diet

contains all ingredients needed to maintain homeostasis- adequate energy, essential amino acids, essential fatty acids, vitamins and minerals

malnutrition

unhealthy state resulting from lack of one or more nutrients

food groups

milk and cheese/ meat, fish, eggs/ fruits/vegetables/ bread, cereal rice

eggs: perfect protein

40/30/30: carbs/ proteins/fat

nitrogen balance

when the amount of nitrogen in your diet equals the amount used and excreted

vitamins

cofactors for reactions

thiamine (water-soluble)

coenzyme in breaking C-C bonds

riboflavin (water-soluble)

part of FAD and FMN

niacin (water-soluble)

part of NAD

B5 (water-soluble)

part of acetyl-CoA

B6 (water-soluble)

coenzyme in amino acids and lipid metabolism

folic acid (water-soluble)

coenzyme in amino acid and nucleic acid metabolism, prevents neural tube defects in babies

B12 (water-soluble)

needed for RBC formation, nucleic acid metabolism

biotin (water-soluble)

coenzyme in breaking C-C bonds

C, ascorbic acid (water-soluble)

coenzyme, delivers H ions, anti-oxidant

A (fat-soluble)

synthesis of visual pigments, supports immune system

D (fat-soluble)

bone growth, Ca and Phosphorus absorption

E (fat-soluble)

prevents breakdown of vit. A and fatty acids, anti-oxidant

K (fat-soluble)

production of prothrobin and clotting factors

minerals

osmotic concentrations, physiological processes, cofactors in enzymatic reactions

sodium(BULK)

membrane function

potassium(BULK)

membrane function

chloride(BULK)

major ion in body fluids

calcium(BULK)

bone structure, muscle and neuron function

phosphorus(BULK)

high energy compounds, nucleic acids

magnesium(BULK)

cofactor of enzymes

sulfur(BULK)

component of proteins, electron carriers

iron(trace)

component of hemoglobin and cytochromes

zinc(trace)

cofactor in enzyme systems

copper(trace)

cofactor for hemoglobin production

manganese(trace)

hemoglobin production and urea formation

cobalt(trace)

needed with B12 for RBC production

selenium(trace)

important anti-oxidant

chromium (trace)

cofactor for glucose metabolism

iodide (trace)

required for thyroid hormones→ regulates metabolism

calories

amount of energy needed to raise a kilogram of water 1 degree C

calories per gram FAT

9.46

calories per gram PROTEIN

4.18

calories per gram CARB

4.32

metabolic rate

some of all the varied anabolic and catabolic processes occurring in the body

basic metabolic rate(BMR)

the minimum resting energy expenditure of an awake, alert person

4.825 calories per liter of O2 consumed, average BMR = 70 C per hour, 1680 C per day

thermoregulation

keeps body temperature within acceptable limits, regardless of environment

radiation- thermoregulation

transfer from hot to cold without contact, greater than 50% of heat loss

conduction- thermoregulation

from hot to cold with physical contact

convection-thermoregulation

from hot to cold from air that overlies surface, 15% of heat loss

evaporation- thermoregulation

water evaporates to cool surface, heat loss is due to change from liquid to gas, 20-25% of heat loss

heat loss

peripheral vasodilation, stimulates sweat glands, depth of respiration increases

heat conservation

decrease blood flow to dermis, and limbs is shunted deeper, countercurrent exchange

shivering- heat generation

gradual increase in muscle tone increases energy consumption of skeletal muscles

non-shivering- heat generation

epinephrine increases glycogenolysis in liver and skeletal muscles