Transcript Necessities of Life Notes - YCUSD Staff Support Forum

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.
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Chapter 2
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.
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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.
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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.
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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.
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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.
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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.
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Comparing Consumers and Producers
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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.
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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.
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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.
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Proteins
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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.
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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.
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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.
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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.
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Section 2 The Necessities of Life
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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.
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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.
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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.
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Concept Map
Use the terms below to complete the concept map
on the next slide.
DNA
sugars
energy
enzymes
living cells
proteins
starches
carbohydrates
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Concept Map
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Chapter 2
It's Alive!! Or Is It?
Concept Map
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