Chapter 7: Energy Systems and Muscle Fibers

Energy Systems

02 not required

Takes place in the cytoplasm

Energy source is creatine phosphate

No by products

1-2 chemical reactions

1 molecule of ATP

10-15s duration

Super quick surge of power

100m sprint

Jump events

Shot put

Fatigue quickly

Takes place in the cytoplasm of cells

Begins with the breakdown of glucose into pyruvate

02 not required

Provides rapid but limited energy for short bursts of intense activity

Due to the accumulation of lactate and depletion of glycogen stores, the glycolytic system is not sustainable for prolonged periods of activity

A net gain of 2 ATP molecules per glucose molecule.

Lactic acid buildup causing a burning sensation in the muscles

Lactic acid is a byproduct

15s-3min duration

Fast surge of power

400m run

Hockey shift

HIIT circuit

Glucose as an energy source

O2 required

Location of activity is the mitochondria

Cells break down glucose and other organic molecules to produce ATP

Cellular respiration produces a large amount of ATP, with oxidative phosphorylation contributing the majority of ATP production

Provides a highly efficient way to extract energy from glucose molecules, maximizing ATP production

Consists of three main stages: glycolysis, the citric acid cycle (Krebs cycle), and oxidative phosphorylation (electron transport chain)

Carbon dioxide and water are produced as waste products.

Produces 36 molecules of ATP

2min and beyond duration

Slow and complete breakdown of glucose

Marathon

Cross-country skiing

Long-distance swimming

Fatigue resistant

Energy source is glycogen, fats and proteins

Cellular Respiration Pathways

Occurs in the cytoplasm of the cell

Begins with one glucose molecule

Produces a net gain of 2 ATP molecules

Produces 2 pyruvate molecules

No oxygen required

Breaks down glucose to provide energy and intermediates for further cellular respiration steps

Occurs in the mitochondria

Provides high-energy electrons for the electron transport chain.

Begins with acetyl-CoA

Produces CO2 as a waste product

Produces a small amount of ATP directly

Inside the inner membrane of the mitochondria

Produces ATP

Oxygen accepts electrons and forms water

Produces most of the cells ATP during respiration

ATP

ATP is the primary energy carrier in all living organisms.

Energy stored in high energy phosphate bonds

Powers the contraction of muscles

Provides energy for cell growth and division

Adenosine Triphosphate

"Free Energy"

Common Energy Molecule

Carbs, fats, and proteins are all resynthesized into this molecule to become usable sources of energy.

Relies on the action of phosphocreatine

ATP is generated through cellular respiration in the mitochondria

Stored in muscle and easily accessible

Nitrogenous base

five carbon sugar molecule

Connected by high energy bonds

Energy sources

Simple sugar, also known as a monosaccharide

Primary energy source of the human body

Essential for brain function, as neurons rely primarily on glucose for energy

During exercise, muscles rely on glucose for energy, especially during high-intensity activities

Belongs to the carbohydrate group, abundant in many foods like fruits, vegetables, and grains

Metabolized through glycolysis, where it is broken down to produce ATP

Excess glucose is stored in the liver and muscles as glycogen for later us

Stored form of glucose

Found in the liver and other muscles

Liver glycogen helps maintain blood glucose levels between meals and during fasting periods

Muscle glycogen provides energy for muscle contraction during exercise

It is a polysaccharide, meaning it consists of multiple glucose molecules linked together

Acts as a readily available energy reserve that can be quickly mobilized when needed

Glycogen is broken down into glucose through glycogenolysis when the body requires energy

During prolonged exercise, muscle glycogen stores can become depleted, leading to fatigue

Glycogen stores are replenished through dietary carbohydrates, particularly after exercise or periods of fasting

High-energy compound

Acts as a rapid and readily available energy reserve for muscle cells during short bursts of intense activity

Provides energy for activities like sprinting, weightlifting, and jumping, where the demand for ATP is immediate and intense

Creatine phosphate stores are quickly depleted during high-intensity activities and are not sustainable for prolonged endurance efforts

Stored primarily in skeletal muscle tissue, with higher concentrations in fast-twitch muscle fibers used for explosive movements

Creatine supplementation is popular among athletes and bodybuilders to enhance short-term performance during high-intensity activities

Creatine is synthesized in the liver and kidneys from amino acids

After use, creatine phosphate can be regenerated during rest periods when ATP demand is lower

Key Nutrients

Fats serve as a dense form of energy storage in the body.

Fatty acids

Glycerol

Saturated or un-saturated

Found in foods like oils, butter, meat, nuts, and avocados

Contain large quantities of stored energy

Found is muscle cells and adipose tissue

Must be consumed with food

Serve as building blocks for cells and tissues, and perform various functions in the body.

Essential for growth and repair

Amino acids

linked together by peptide bonds

20 different amino acids, each with a unique side chain

Some amino acids are essential, meaning they must be obtained from the diet

Found in foods like meat, fish, eggs, dairy, legumes, nuts, and seeds

No protein reserve

Main source of energy for the body, especially for the brain and muscles

Dietary guidelines suggest consuming a majority of calories from carbohydrates, mainly from whole food sources

Composed of carbon, hydrogen, and oxygen atoms in a ratio of 1:2:1

Include sugars, starches, and fibers

Simple vs Complex carbohydrates

Simple Carbs: Rapidly digested sugars found in foods like fruits, candies, and soft drinks

Complex Carbs: Starches and fibers found in foods like grains, vegetables, and legumes

Found in foods like bread, rice, pasta, fruits, vegetables, and dairy products

Glucose & Glycogen

Muscle Fibers

2-3x faster contractions than slow twitch fibres

Paler in colour

Tense and relax quickly

Generate large amounts of tension with low endurance levels

Fast-oxidative glycolytic

Intermediate force production

Low energy efficiency

Hockey shift

Red or dark colour

Generate and relax tension

Maintain lower level of tension for longer duration

Long-distance ideal

Fatigue resistant

Generate energy slowly

Mainly depend on anaerobic processes

Slow-oxidative

Marathon

Myoglobin

A protein that stores oxygen in muscle cells

It has a globular structure, similar to hemoglobin

Gives muscles their reddish color.

Has a higher affinity for oxygen than hemoglobin, making it efficient at storing oxygen in muscles

Facilitates oxygen delivery to muscle tissues during periods of increased activity

Abundant in skeletal and cardiac muscle cells

Helps muscles sustain aerobic activity by providing oxygen when needed