Supplying Energy

Supplying Energy

Middle School

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Learning Objectives

• Trace the path of energy from food to ATP within a cell.

• Explain the roles of the digestive, respiratory, and circulatory systems in supplying energy.

• Compare aerobic and anaerobic ATP production and when each is used by the body.

• Describe how glycogen and fat are used as energy stores managed by insulin and glucagon.

• Predict changes in breathing, heart rate, and fuel use during exercise and recovery periods.

Key Vocabulary

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ATP

The molecule that cells directly use to power their many activities and functions.

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Mitochondrion

The specialized part of a cell where aerobic respiration occurs to produce most ATP.

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Aerobic Respiration

The process of creating a large amount of ATP from glucose and fat using oxygen.

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Anaerobic Glycolysis

The rapid creation of a small amount of ATP from glucose without requiring oxygen.

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Lactate

A substance produced during anaerobic glycolysis that signals fatigue during intense, short-term exercise.

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Glycogen

The body's stored form of glucose, found in the liver and muscles for quick energy.

Key Vocabulary

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Fatty Acid

A primary component of fat that serves as a very dense, long-term energy source for the body.

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Hemoglobin

The essential protein in red blood cells that binds to and transports oxygen throughout your body's tissues.

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Alveolus

A tiny, functional air sac in the lungs where oxygen enters the blood from the air you breathe.

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Capillary

The smallest type of blood vessel where nutrients and oxygen are exchanged between blood and body cells.

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Creatine Phosphate

Creatine Phosphate (PCr) is a compound in muscles that rebuilds ATP for short, explosive bursts of power.

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Insulin

A key hormone that helps your body's cells absorb glucose and promotes energy storage as glycogen.

Key Vocabulary

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Glucagon

A hormone that signals the liver to release its stored glucose into the bloodstream.

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Epinephrine

A hormone that triggers a rapid release of both glucose and fats for immediate energy.

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From Food to Fuel: The Big Picture

• Food provides potential chemical energy that the body turns into a usable form called ATP.

• Carbohydrates are the main source of quick energy, breaking down into glucose.

• Fats are a dense energy source, and proteins are for building and repair.

• Vitamins and minerals act as helpers to enable energy-releasing chemical reactions.

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Multiple Choice

What is the main purpose of food for the body, as described in the 'From Food to Fuel' model?

• To provide chemical energy that is converted into a usable form called ATP.

• To supply the body with materials for building and repair only.

• To act as helpers for chemical reactions in the body.

• To be immediately stored as a dense energy source for later use.

Multiple Choice

How does the primary role of carbohydrates differ from the primary role of proteins in the body?

• Carbohydrates are the main source of quick energy, while proteins are primarily for building and repair.

• Carbohydrates are for building and repair, while proteins are the main source of quick energy.

• Both carbohydrates and proteins are used mainly as dense, long-term energy sources.

• Both carbohydrates and proteins act as helpers for energy-releasing chemical reactions.

Multiple Choice

If a person's diet contains plenty of carbohydrates and fats but is missing vitamins and minerals, what is the most likely impact on their body's ability to produce energy?

• Energy production would be less efficient because the chemical reactions that release energy would be hindered.

• The body would produce extra ATP because it has plenty of carbohydrates and fats for fuel.

• The body would start breaking down proteins for energy instead of for repair.

• Energy production would not be affected as long as fuel from food is available.

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Step 1: Digest, Absorb, and Deliver

Digestion

• The digestive system uses enzymes to break down large food molecules into smaller nutrient molecules.

• Amylase in the mouth and pepsin in the stomach begin to break down carbohydrates and proteins.

• In the small intestine, nutrients are fully broken down into glucose, amino acids, and fatty acids.

Absorption & Delivery

• The walls of the small intestine have tiny structures called villi that absorb these nutrient molecules.

• Fats enter vessels called lacteals, while glucose and amino acids go directly into the blood.

• The heart then pumps this nutrient-rich blood through tiny capillaries to deliver fuel to every cell.

Multiple Choice

What is the primary function of enzymes like amylase and pepsin in the digestive system?

• To break down large food molecules into smaller nutrient molecules.

• To store food until the body needs energy.

• To absorb water and electrolytes from undigested food.

• To pump nutrient-rich blood to all the cells in the body.

Multiple Choice

What is the relationship between the villi in the small intestine and the delivery of nutrients to the body?

• The stomach uses villi to break down proteins into amino acids.

• Villi absorb nutrients, which then enter the blood and lacteals for delivery.

• The heart pumps blood directly to the small intestine to digest food.

• Amylase and pepsin are absorbed by villi to enter the bloodstream.

Multiple Choice

If the digestive system successfully breaks down and absorbs nutrients but the heart stops pumping blood effectively, what would be the ultimate consequence for the body's cells?

• Enzymes would stop breaking down carbohydrates and proteins.

• The delivery of fuel to the body's cells would fail.

• Fats would be absorbed directly into the blood instead of lacteals.

• The villi would be unable to absorb any nutrient molecules.

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Step 2: Making ATP - The Cell's Energy Money

Aerobic Respiration

• This is the main way cells generate energy when oxygen is present and it happens inside the mitochondria.

• It breaks down glucose completely, producing a large amount of ATP, the cell's main energy currency.

• The waste products are carbon dioxide and water, following the formula: glucose + oxygen → CO₂ + water + ATP.

Anaerobic Respiration

• This process kicks in when your body needs energy faster than oxygen can be supplied for short bursts.

• It works without oxygen, producing a small amount of ATP very quickly for immediate power needs.

• This type of respiration also produces a substance called lactate, which can build up in the muscles.

Multiple Choice

What is the main energy currency that cells produce during both aerobic and anaerobic respiration?

• ATP

• Lactate

• Carbon dioxide

• Glucose

Multiple Choice

What is a primary difference between aerobic and anaerobic respiration?

• Aerobic respiration requires oxygen and produces a large amount of ATP, while anaerobic respiration does not.

• Anaerobic respiration occurs in the mitochondria, while aerobic respiration occurs in the cytoplasm.

• Aerobic respiration produces lactate, while anaerobic respiration produces carbon dioxide and water.

• Anaerobic respiration breaks down glucose completely, while aerobic respiration breaks it down partially.

Multiple Choice

In which of the following scenarios would muscle cells rely most heavily on anaerobic respiration for energy?

• A sprinter running a 100-meter dash, because their body needs a small amount of ATP very quickly.

• A person sleeping through the night, because their body is not using any oxygen.

• A hiker walking on a flat trail for an hour, because their muscles are producing a lot of lactate.

• A student sitting and reading a book, because their mitochondria are working without oxygen.

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Step 3: Supplying the Oxygen

• For aerobic respiration, your cells require a constant supply of oxygen.

• The respiratory system brings oxygen into the lungs' alveoli, where it enters the blood.

• In red blood cells, oxygen binds to a protein called hemoglobin.

• Your heart rate adjusts to pump oxygen-rich blood effectively to your tissues.

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Multiple Choice

What is the primary reason your cells require a constant supply of oxygen?

• To perform aerobic respiration.

• To cool down the body's tissues.

• To remove waste from the blood.

• To create new red blood cells.

Multiple Choice

What is the specific role of hemoglobin in supplying oxygen to the body's tissues?

• It moves from the lungs into the alveoli.

• It is a part of the heart that pumps blood.

• It binds to oxygen in red blood cells for transport through the blood.

• It is the cell that performs aerobic respiration.

Multiple Choice

During physical exercise, the body's tissues need more energy. Based on this, what is the most likely response of the circulatory system?

• The heart rate increases to deliver oxygen-rich blood to the muscles more quickly.

• The heart rate decreases to conserve oxygen for the brain.

• Hemoglobin stops binding to oxygen to save it for later.

• The alveoli close to prevent too much oxygen from entering the blood.

Energy Systems on Different Time Scales

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Immediate Energy (0-10s)

• ​The body uses the ATP already stored in your muscles for energy.

• ​​Creatine Phosphate helps rebuild ATP for brief, powerful bursts of activity.

• ​This system is ideal for a heavy weight lift or a jump.

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Short-Term (10s - 2min)

• ​The body breaks down glucose without oxygen to make ATP very quickly.

• ​​This process is used for events like running a 400-meter sprint.

• ​A byproduct of this energy system is the production of lactate.

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Long-Term Energy (>2min)

• ​The aerobic system uses oxygen to produce large amounts of ATP.

• ​​It breaks down both carbohydrates and fats to create sustained energy.

• ​This system powers long activities like running a marathon for hours.

Multiple Choice

What is the main factor that determines which of the body's energy systems is used for an activity?

• The duration of the activity.

• The time of day the activity is performed.

• The amount of water a person drinks.

• The type of equipment used.

Multiple Choice

What is a key difference between how the body produces energy for a short sprint versus a long marathon?

• Energy for a sprint is made with oxygen, while energy for a marathon is made without it.

• Energy for a sprint is made without oxygen, while energy for a marathon requires oxygen.

• Sprints are powered by breaking down fats, while marathons are powered by stored ATP.

• Sprints get energy from creatine phosphate, while marathons get energy from lactate.

Multiple Choice

An athlete performs a maximum-effort sprint that lasts for 90 seconds. After the first 10 seconds, what is the most likely way the athlete's body will produce energy for the rest of the sprint?

• The body will use its aerobic system to break down fats for sustained energy.

• The body will continue to use stored ATP and creatine phosphate for the entire duration.

• The body will rely on breaking down glucose without oxygen, leading to the production of lactate.

• The body will immediately switch to using oxygen to power the rest of the sprint.

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Energy Storage and Hormonal Control

• Glucose is stored as glycogen in the liver and your muscles.

• Liver glycogen keeps blood glucose steady; muscle glycogen fuels muscle work.

• Fat is the body's most efficient long-term energy storage fuel.

• Insulin stores energy, while glucagon and epinephrine release stored energy.

Multiple Choice

What are the primary ways the body stores energy for short-term and long-term needs?

• As glycogen for short-term use and fat for long-term use.

• As insulin for short-term use and glucagon for long-term use.

• As muscle for short-term use and adipose tissue for long-term use.

• As glucose for short-term use and protein for long-term use.

Multiple Choice

What is the relationship between eating a meal and the hormone insulin?

• After a meal, insulin is released to help the body store energy.

• After a meal, insulin is released to help the body burn fat immediately.

• Insulin is released when you are hungry to make you want to eat a meal.

• Insulin breaks down glycogen into glucose after a meal.

Multiple Choice

A person goes for a long run several hours after their last meal. Which hormones are most likely released to provide their muscles with the energy they need?

• Glucagon and epinephrine to release stored energy.

• Insulin to help store any remaining energy.

• Glucagon to store fat and epinephrine to store glycogen.

• Insulin and glucagon to create new energy.

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Common Misconceptions

Misconception	Correction
Protein is the body's main fuel for energy.	Carbohydrates and fats are the main fuel; protein is for building and repair.
Your body cannot make ATP without enough oxygen.	Your body can make ATP without oxygen for short bursts of activity.
The liver’s only role is in digestion.	The liver also stores and releases glucose to regulate your body's energy.
Energy needs are normal right after exercise.	Breathing stays high after exercise to repay an 'oxygen debt.'

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Summary

• Body systems work together to convert food into fuel and deliver it to cells.

• Aerobic respiration provides long-lasting energy, while anaerobic respiration gives quick power bursts.

• The body stores energy as glycogen and fat, which is managed by hormones.

• Exercise recovery requires extra oxygen to replenish ATP and restore balance.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1 (Not confident)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)