1. Chapter 2
Section 2 The Necessities of Life
Bellringer
Most cells are made up of about 70% water. What would your mass be if there was no water in your body?
Write your answer in your science journal.

2. Chapter 2 What You Will Learn
Section 2 The Necessities of Life
What You Will Learn
The cells of every living thing need water and food in order to function properly.
Proteins, carbohydrates, lipids, ATP, and nucleic acids are molecules that support the functions of cells.

3. Chapter 2
Section 2 The Necessities of Life
Water
Every living thing needs water, food, and a place to live in order to survive.
Water makes up about 70% of your cells. This is true for almost all living things.
Water is needed for most of the chemical reactions involved in metabolism.

4. Chapter 2
Section 2 The Necessities of Life
Air
Air is a mixture of gasses, mostly nitrogen and oxygen, with some other gasses like carbon dioxide.
Most living things, including plants, use oxygen to release energy from food. Plants also need carbon dioxide to make food.
Some organisms can live without air and are called anaerobic.

5. Chapter 2
Section 2 The Necessities of Life
A Place to Live
All organisms need a place to live that has all of the things they need to survive.
Often organisms compete for the best places to live. Space is limited, especially space that includes food, water, and other necessities.
The amount of space needed to survive varies from organism to organism.

6. Chapter 2
Section 2 The Necessities of Life
Food
All living things need food for energy and the raw materials to make cells and build body parts.
Organisms can be divided into three groups based on how they get their food: producers, consumers, and decomposers.
Producers make their own food through photosynthesis. Producers include plants, algae, and some types of bacteria.

7. Chapter 2 Food, continued
Section 2 The Necessities of Life
Food, continued
Consumers must eat other organisms, such as plants or animals, to get food.
Decomposers are a group of consumers that get their food from breaking down the nutrients in dead organisms and their wastes.
A mushroom, or fungus, is a type of decomposer.

8. Comparing Consumers and Producers
Chapter 2
It's Alive!! Or Is It?
Comparing Consumers and Producers

9. Putting It All Together
Chapter 2
Section 2 The Necessities of Life
Putting It All Together
Producers, consumers, and decomposers must all break down their food to use the nutrients.
Nutrients are made of molecules. A molecule is made from two or more atoms joined together.
Molecules made of more than one type of atom are called compounds.

10. Putting It All Together, continued
Chapter 2
Section 2 The Necessities of Life
Putting It All Together, continued
The most common atoms, or elements, that make the compounds found in nutrients are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.
These elements join together to form proteins, carbohydrates, lipids, ATP, and nucleic acids.

11. Chapter 2
Section 2 The Necessities of Life
Proteins
Almost all life processes of a cell involve proteins.
Proteins are large molecules made of amino acids. Amino acids are used to build new proteins for body repair, growth, and to regulate processes in the body.
Hemoglobin is a protein in red blood cells. Enzymes are proteins that speed up chemical reactions.

12. Chapter 2
It's Alive!! Or Is It?
Proteins

13. Chapter 2 Carbohydrates
Section 2 The Necessities of Life
Carbohydrates
Molecules made of sugars are called carbohydrates. They provide energy for the cell, and store energy for later use.
Simple carbohydrates are made up of one or a few sugar molecules.
Table sugar and fruit sugar are simple carbohydrates.

14. Carbohydrates, continued
Chapter 2
Section 2 The Necessities of Life
Carbohydrates, continued
Complex carbohydrates may contain hundreds of sugars in long chains.
Complex carbohydrates are used for storage of extra sugar.
Starch is an example of a complex carbohydrate.

15. Chapter 2
Section 2 The Necessities of Life
Lipids
Lipids are fat molecules. Lipids cannot mix with water.
Like complex carbohydrates, some lipids store energy. Other lipids form the membranes of cells.
All cells are surrounded by a cell membrane that protects the cell and helps to maintain homeostasis.

16. Chapter 2 Lipids, continued
Section 2 The Necessities of Life
Lipids, continued
Phospholipids are a type of lipid molecule that form much of the cell membrane.
The head of a phospholipid molecule is attracted to water. The tail of the phospholipid is repelled by water.
The properties of phospholipids cause the tails of individual molecules to come together, forming a two layer membrane.

17. Chapter 2
Section 2 The Necessities of Life

18. Chapter 2 Lipids, continued
Section 2 The Necessities of Life
Lipids, continued
The two layer-membrane protects the cell by making it difficult for materials to move into or out of the cell.
Fats and oils are also lipids. Both fats and oils store energy, but most fats are solid at room temperature, and most oils are liquid.

19. Chapter 2
Section 2 The Necessities of Life
ATP
Adenosine triphosphate, or ATP, is another important molecule. ATP is the main energy source for cellular activities.
Energy in carbohydrates and lipids must first be transferred to ATP before in can be used by cells.

20. Chapter 2
Section 2 The Necessities of Life
Nucleic Acids
Nucleic Acids are molecules that carry the directions for making proteins.
DNA is a nucleic acid. Nucleic acids are made of chains of smaller molecules called nucleotides.
The sequence of nucleotides tells the cell how to arrange the amino acids to make the protein.

21. Chapter 2
It's Alive!! Or Is It?
Concept Map
Use the terms below to complete the concept map on the next slide.
DNA
sugars
energy
enzymes
living cells
proteins
starches
carbohydrates

22. Chapter 2
It's Alive!! Or Is It?
Concept Map

23. Chapter 2
It's Alive!! Or Is It?
Concept Map