Lec 1

Metabolism

- sum of chemical changes that convert nutrients into energy and the finished products of the cell.
- greek for change
- interconnected pathways involving production of energy + synthesis of molecules using energy

Pathway

A series of consecutive reactions that can be linear, cyclic, or branched.

linear pathway example

glycolysis

cyclic pathway exmaple

citric acid cycle

branched pathway example

amino acid metabolism

Macronutrients

Nutrients required in large amounts, including fats, carbohydrates, and proteins.

forms of energy

atp, gtp

Micronutrients

Nutrients required in smaller amounts, including vitamins and minerals.

A>a>B>b>C>c>D>d>E>e

- inital substrate = A
- final product = E
- enzyme = b,c,d,e
- intermediates = B,C,D
- metabolites = A,B,C,D,E

reactions are catalyzed by

enzymes

ATP

Adenosine triphosphate, the primary energy carrier in cells.

Anabolism

synthesis of complex molecules from simpler ones

ex of anabolism

gluconeogenesis.

Catabolism

breakdown of complex molecules into simpler ones (degradative)

ex catabolism

glycolysis

traits of anabolytic/catabolytic pathways

- distinct enzymes that catalyze irreversible reactions
- cannot operate simultaneously (futile cycling, substrate cycling)

futile cycling/substrate cycling

- 2 metabolic pathways run simultaneously in opposite directions
- has no overall effect
- dissipate energy in the form of heat.

pathways are controlled by

- allosteric regulation
- covalent regulation by phosphrylation

Enzyme

A protein that catalyzes biochemical reactions, facilitating metabolic pathways.

Allosteric regulation

A form of regulation where the activity of an enzyme is modified by the binding of an effector molecule.

Compartmentalization

- localization of enzymes and metabolites in specific organelles to enhance metabolic efficiency
- maintains separate pools of enzymes/metabolites/cofactors for seperate processes
- requires specific transport proteins
- offers control regulation

increased efficiency of assembly line

- localizing enzymes for glycolysis/citric acid in one location
- diffusion distance reduced

In vivo

- Studies conducted in living organisms, reflecting complex biological systems.
- no complete control over conditions

In vitro

- Studies conducted outside of living organisms, often in controlled laboratory conditions.
- difficult to extrapolate from controlled experiment
- not under physiological conditions

organizational levels of study

whole organism > isolated organism > tissue > whole cell > cell extract > purified components (isolated mitochondria/enzyme)

tools to study metabolism

- metabolic probes
- radiotope labels

important of studying metabolism

- need for energy (work, active transport, molecule biosynthesis)
- understand etiology of metabolic errors (PKU, diseases)
- diet (weight loss, diabetes)
- manufacturing food products
- studying hibernation/estivaition

BMI

Body Mass Index, a measure used to rank obesity based on weight and height.

BMI formula

= weight (kg) / height (m²)

normal BMI

20

overweight bmi

25

obese bmi

30

fat basic unit and storage

- basic unit: free fatty acid
- storage form: triglycerides

where is fat found and in which form

- muscle: triglycerides
- adipose tissue: triglycerides
- blood plasma: free fatty acid

carbohydrate basic unit and storage

- basic unit: glucose
- storage form: glycogen

where are carbs found and in which form

- liver. muscle: glycogen
- blood/plasma: glucose

protein basic unit and storage

- basic unit: amino acid
- storage form: muscle protein

where are proteins found and in which form

muscle: protein

muscle accounts for ___ total body mass

½
*muscle is also major consumer of glucose

muscle contraction is caused by

cycling of actin-myosin cross bridges in cytoplasm

ATP is hydrolyzed by

actomyosin ATPase

rate of ATP turnover varies with

tissue and metabolic activity

ATP stores are

finite
*must be continously replenished and resynthesized

from rest to maximal exercise ATP turnover in muscles can

increase 100 fold

muscle cells only have enough ATP to maintain

1-2 secs of maximal sprint exercise

what is highest energy demanding tissue of human body

brain (consumes 20% oxygen + ¼ glucose)

inverse relation btw

exercise intensity and duration of exercise

fuel availability ranking

1) PCr
2) carbs
3) fat

as intensity increases

- turnover increases
- carb fuel selection increases (fats used less)

PCr (phosphocreatine)

- high-energy compound that rapidly replenishes ATP during short bursts of activity.

ATP is replenished at site of contraction by

substrate phosphrylation of ADP by PCr

PCr + ADP =

ATP + Cr

what catalyzed phosphate transfer

creatine kinase (CK)

PCr shuttle

shuttles energy from site where ATP is made (mitochondria) to where it is required in cell (bc no efficent method for ATP to diffuse rapidly)
clusters of CK scattered througout cell to ensure PCr transfer

Phosphagen system

A metabolic pathway that uses PCr to quickly regenerate ATP during high-intensity exercise.

Creatine Kinase (CK)

An enzyme that catalyzes the transfer of a phosphate group from PCr to ADP to form ATP.

Ergogenic aids

Substances ingested to enhance physical performance and exercise capacity.(ergo-work)

ATP stores last

1-2 sec during maximal exercise

PCr stores offer energy for another

10 secs

Creatine supplementation

The practice of ingesting creatine to increase muscle creatine and PCr stores.

endogenous creatine

amino acid derivatives synthesized in body (glycine, arginine, methionine)

exogenous creatine

dietary intake (1-2 g/day)

storage of creatine in body

- skeletal muscle (95% - 60% stores as PCr)
- 5% in brain, liver, kidney, testes

role of PCr during exercise

- impt during high intesnity exercise + first few secs of exercise
- gives 50-70% energy in first 2-10 secs

key takeaways

- atp preserved bc of creatine
- during rest pcr stores replenished
- atp pretty consistent btw bouts

loading phase

3g/day for 28 days

Loading phase

A period of increased creatine intake to boost muscle creatine levels.
a) loading phase
b) loading + maintenance

loading + maintenance

- loading: 20g/day for 5 days
- mainthenance: 2g/day

creatine study results

top: loading phase only, creatine levels dropped
bottom: loading + maintenance, creatine levels maintained

mechanism of creatine loading

– Increases short-term power output by increasing PCr/Cr
energy stores
- increase intensity of contraction
– Enhances resynthesis of PCr during recovery - lowers fatigue
- increase volume of training
– Reduces reliance on glycolysis (less lactate production)
– May delay breakdown of muscle glycogen
– Consumes H +, and thus reduces lactic acidosis

concerns with studies

- Results are variable and often conflicting due to
– different experimental exercise protocols
– inter-individual variations in response to supplementation
- Most beneficial for sports involving
– short bouts of high intensity activity
– repetitive bouts of high intensity activity (sprinting/cycling,
weight lifting)

Side effects of creatine

Potential adverse effects including gastrointestinal upset, muscle cramps, and renal dysfunction.
no short term studies have demonstrated these side effects