EX phys: Energy

Energy

Capacity to perform work

Work

Application of force thru a distance

WORK= F x d

If there is no displacement, no mechanical work is done (physics definition).

Force

THAT which tends to produce motion

Power

Rate of performing work

(also has a lot to deal with quality of life)

How quickly work is performed

First Law of Thermodynamics states that

(conservation of energy): energy cannot be created or destroyed, only transformed or transferred between forms.

Forms of Energy

1. Chemical engery(food)

2. Heat(sun)

3. Mechanical( human motion, Bones & muscles)

4. Light (sun)

5. Electrical(nervous system)

6. Nuclear(sun)

3 Main food sources

1. Carbs

2. Protein

3. Fat

98-99% Comes from Carbs and fat

1-2% comes from Protien

ATP

adenosine triphosphate; the usable chemical energy form for cells.

• Adenosine = adenine + ribose (“-ose” = sugar)

• Three phosphate groups (terminal phosphoanhydride bonds are “high-energy”)

Conceptual structure

Enzymes

• Protein catalysts that speed reactions; many end in “-ase” (e.g., ATPase).

• Enzyme names indicate function (e.g., kinases transfer phosphate groups).

The only form of cells can directly use for biological work

ATP

___ is stored in muscle only in small amounts.

ATP

During maximal all-out efforts, PCr falls rapidly while ATP initially stays near resting levels due to rapid resynthesis. When PCr is depleted (after ~8–10 s), ATP production cannot match demand, ATP concentration falls, and performance degrades (fatigue).

Fatigue

Product of ATP hydrolysis (adenosine + two phosphates); can be rephosphorylated to ATP.

ADP

Free phosphate released during ATP hydrolysis; can be reattached to ADP to reform ATP.

Pi(Inorganic phosphate)

The terminal phosphate bonds in ATP and PCr whose hydrolysis liberates usable energy for cellular work.

High-energy (phosphoanhydride) bonds

A chemical reaction using water to break a bond; in this context, ATP + H2O —(ATPase)—> ADP + Pi + energy.

Hydrolysis

How many seconds do we have stored in the muscle for ATP?

2 SECONDS

A creatine molecule bonded to a phosphate via a high-energy bond; donates phosphate to ADP to quickly reform ATP.

Phosphocreatine (PCr / CP / creatine phosphate)

The non-phosphorylated form found in muscle cells; can be phosphorylated to form PCr. (Note: oral creatine monohydrate supplements are related but not identical to PCr.)

Creatine (intracellular):

The reversible enzyme (a kinase) that transfers phosphate between PCr and ADP: ADP + PCr —(CK)—> ATP + creatine.

Creatine kinase (CK)

Enzyme that catalyzes ATP hydrolysis to ADP + Pi, releasing energy for biological work (e.g., muscle contraction cross-bridge cycling uses ATPase activity).

ATPase:

Enzymes that transfer phosphate groups; creatine kinase transfers phosphate between PCr and ADP/ATP.

Kinase (naming convention)

Reversible reaction (PCr ↔ ATP)

The CK-catalyzed reaction is reversible, allowing PCr to donate phosphate to ADP to form ATP and, under other conditions, ATP to phosphorylate creatine.

Activities primarily supported by ATP–PC:

Very short,

maximal-power efforts such as single maximal sprints (initial phase),

shot put,

single maximal weight lifts, throws, explosive jumps, and singular maximal actions in team sports (e.g., a single block, kick, or swing).

System limitations for prolonged exercise

The ATP–PC system cannot sustain prolonged activity; for efforts beyond ~10 s at high intensity, glycolysis (anaerobic carbohydrate metabolism) and aerobic oxidative phosphorylation are needed.

Pathways that regenerate ATP without using oxygen (ATP–PC system and glycolysis).

Anaerobic systems

Oxygen-dependent, multi-step ATP production pathway with higher capacity but slower power output; covered in later lectures.

Aerobic metabolism (oxidative phosphorylation):

How ATP is used at the molecular level to power actin–myosin interactions (sliding filament theory) — topic for further lectures.

Cross-bridge / muscle contraction coupling