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Chapter 4
The Cell in Action
Table of Contents
Section 1 Exchange with the Environment
Section 2 Cell Energy
Section 3 The Cell Cycle
Chapter 4
Section 1 Exchange with the
Environment
Objectives
• Explain the process of diffusion.
• Describe how osmosis occurs.
• Compare passive transport with active transport.
• Explain how large particles get into and out of cells.
Chapter 4
Section 1 Exchange with the
Environment
What Is Diffusion?
• Diffusion is the movement of particles from regions
of higher density to regions of lower density.
• Diffusion of Water The diffusion of water through
cell membranes is called osmosis.
Chapter 4
Section 1 Exchange with the
Environment
What Is Diffusion?, continued
• The Cell and Osmosis Osmosis is important to
cell functions.
• Plasma surrounds red blood cells and is made up
of water, salts, sugars, and other particles. Osmosis
keeps the concentration of these particles in balance.
• When a wilted plant is watered, osmosis makes the
plant firm again.
Chapter 4
Section 1 Exchange with the
Environment
Moving Small Particles
• Passive Transport The movement of particles
across a cell membrane without the use of energy by
the cell is called passive transport.
• Active Transport A process of transporting
particles that requires the cell to use energy is called
active transport.
Chapter 4
Section 1 Exchange with the
Environment
Chapter 4
Section 1 Exchange with the
Environment
Moving Large Particles
• Endocytosis The active-transport process by which
a cell surrounds a large particle and encloses the
particle in a vesicle to bring the particle into the cell is
called endocytosis.
• Exocytosis The process in which a cell releases a
particle by enclosing the particle in a vesicle that then
moves to the cell surface and fuses with the cell
membrane is called exocytosis.
Chapter 4
Section 1 Exchange with the
Environment
Chapter 4
Section 2 Cell Energy
Objectives
• Describe photosynthesis and cellular respiration.
• Compare cellular respiration with fermentation.
Chapter 4
Section 2 Cell Energy
From Sun to Cell
• Photosynthesis is the process by which plants,
algae, and some bacteria use sunlight, carbon
dioxide, and water to make food.
• Chlorophyll Plant cells have molecules that
absorb light energy. These molecules are called
pigments. Chlorophyll, the main pigment used in
photosynthesis, gives plants their green color.
Pigments and Spectrum of light
Chapter 4
Section 2 Cell Energy
From Sun to Cell, continued
Chapter 4
Section 2 Cell Energy
Getting Energy from Food
• Cellular Respiration During cellular respiration,
food (such as glucose) is broken down into carbon
dioxide and water, and energy is released.
Chapter 4
Section 2 Cell Energy
Getting Energy from Food, continued
• Connection Between Photosynthesis and
Respiration During photosynthesis, cells take in
carbon dioxide and release oxygen. During cellular
respiration, cells use oxygen to break down glucose
and release energy and carbon dioxide.
• Fermentation When muscles can’t get the oxygen
for cellular respiration, they use fermentation to get
energy. Fermentation is the breakdown of food
without the use of oxygen.
Chapter 4
Section 2 Cell Energy
Chapter 4
Section 3 The Cell Cycle
Objectives
• Explain how cells produce more cells.
• Describe the process of mitosis.
• Explain how cell division differs in animals and
plants.
Chapter 4
Section 3 The Cell Cycle
The Life of a Cell
• The cell cycle begins when the cell is formed and
ends when the cell divides and forms new cells.
• Before a cell divides, it must make a copy of its
DNA which is organized into structures called
chromosomes.
Cell Cycle
G1 Phase
S Phase
G2 Phase
M Phase
Chapter 4
Section 3 The Cell Cycle
The Life of a Cell, continued
• Making More Prokaryotic Cells Cell division in
bacteria is called binary fission, which means
“splitting into two parts.”
• Bacteria have a single circular DNA molecule
(chromosome). Binary fission results in two cells that
each contain one copy of the circle of DNA.
Chapter 4
Section 3 The Cell Cycle
The Life of a Cell, continued
•Eukaryotic Cells and Their DNA The chromosomes
of eukaryotic cells contain more DNA than those of
prokaryotic cells.
•In a eukaryotic cell, chromosomes are found in the
nucleus and are made of DNA and protein.
• Pairs of similar chromosomes are called homologous
chromosomes.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Chapter 4
Section 3 The Cell Cycle
The Life of a Cell, continued
The cell cycle has three stages:
1. Interphase: The cell grows and copies its
chromosomes. The two copies are now called
chromatids.
2. Mitosis: The chromatids separate.
3. Cytokinesis: The cell splits into two identical
cells.
Chapter 4
Section 3 The Cell Cycle
Mitosis and the Cell Cycle
• Mitosis has four phases:
1. prophase
2. metaphase
3. anaphase
4. telophase
Chapter 4
Section 3 The Cell Cycle
Mitosis and the Cell Cycle, continued
• Cytokinesis is the division of cytoplasm.
• In animal cells and other eukaryotes that do not have
cell walls, division of the cytoplasm begins at the cell
membrane.
• In plant cells and in other eukaryotes with cell walls,
a cell plate forms and the cell splits into two cells.
Chapter 4
Section 3 The Cell Cycle
Chapter 4
The Cell in Action
Concept Map
Use the terms below to complete the concept map on
the next slide.
ATP
photosynthesis
oxygen
water
consumers
lactic acid
producers
respiration
energy
Chapter 4
The Cell in Action