Chapter 7: Energy for Life

Unit B: Understanding Common Energy Conversion Systems

7.1 Nature’s Energy Conversion Cells of green plants have special parts that

capture solar energy and convert it into energy for the plants (food) These cells are called CHLOROPLASTS

Chloroplasts also contain chlorophyll. Chlorophyll assists in converting carbon dioxide

and water into glucose and oxygen. This process is know as photosynthesis

Equation: Sunlight + CO2 + H20 Glucose and O2

7.1 Nature’s Energy Conversion Cellular respiration is how plants and animals

obtain energy from food Cellular respiration takes place in the

mitochondria

Equation: Glucose + O2 energy + H20 + CO2

Why is cellular respiration important?

7.1 Nature’s Energy Conversion Two Energy Conversions

Input energy converter output energy

This equation shows the energy conversion in plants Solar energy chloroplasts in plant leaf glucose

This equation shows the energy conversion in animals Glucose mitochondria kinetic energy

7.1 Nature’s Energy Conversion When any energy conversion happens, a

certain amount of energy is lost.

Only about 10 percent of energy is passed from one level to the next

7.2 The Need for Energy Homeostasis

No matter what is happening outside your body, your body will remain approximately 37 degrees Celsius.

How does your body remain around 37 degrees Celsius?

The rate at which your body uses energy is metabolism. Someone who has a high metabolism has high

energy needs

7.3 Sources of Energy The main source of energy for humans are

simple carbohydrates (glucose) If we take in more glucose than necessary, it

will be converted to glycogen Glycogen is a starch-like substance that is stored

in the liver and muscles

Carbohydrates are the most direct source of energy

7.3 Sources of Energy Fats

2 types of fats: Saturated and Unsaturated

Saturated fats come from animal fats and some oils Increased risk of heart disease

Unsaturated fats come from healthier oils Decreased risk of heart disease

7.3 Sources of Energy One gram of protein contains the same

energy as one grain of carbohydrate. The difference is that it is more difficult for the

body to break it down

Only 10% of our daily intake should be protein Examples of protien:

However proteins are still extremely important, protiens are the building blocks of our physical body

7.4 Human Energy Needs Change

4 things that affect our metabolism: Age, time of day, exercise, level of fitness

Age: Younger people have higher metabolisms

Time of Day: Our metabolism peaks at 10:00am

Exercise: Activity raises metabolism Level of fitness: Use a large amount of energy

getting and keeping in shape