Introduction to Cells

Section 7-1

Key Idea: Microscope

observations of organisms

led to the discovery of

the basic characteristics

common to all living

things.

Observations made by

scientists using more

powerful microscopes in

the 1800s led to the

formation of the cell

theory.

How powerful was Hooke’s

microscope?

Hooke’s microscope could

magnify objects to 30 times

their normal size.

Key Idea: A cell’s shape

reflects its function.

The word dimension means

cells can be branched, flat,

round, or rectangular.

Cell size is limited by a cell’s

surface area-to-volume ratio.

Cells with greater surface

area-to-volume ratio can

exchange substances more

efficiently.

Small cells have greater

surface area-to-volume

ratios than large cells.

So, small cells function

more efficiently than

large cells.

How does a cell’s size

affect the cell’s function?

Smaller cells can exchange

substances more efficiently

than larger cells of the

same shape and size.

Key Idea: All cells have

common structural

features including a cell

membrane, cytoplasm,

ribosomes, and DNA.

A cell membrane is the outer

layer that covers a cell’s surface

and acts as a barrier between the

outside environment and the

inside of the cell.

Cytoplasm is the region of the

cell within the cell membrane.

The cytoplasm includes the fluid

inside the cell called the cytosol.

A ribosome is a cellular structure

that makes proteins.

Prokaryotic Cell Eukaryotic Cell

A prokaryote is an

organism that is a single

prokaryotic cell.

A eukaryote is an

organism that is made

up of one or more

eukaryotic cells.

The nucleus is an internal

compartment of the cell

that contains the DNA of a

eukaryotic cell.

An organelle is a small

structure found in the

cytoplasm that carries out

specific activities inside

the cell.

Prokaryotic cells do not

have a nucleus or other

internal compartments.

The genetic material of a

prokaryotic cell is a single

loop of DNA.

Each organelle is a

eukaryotic cell performs

distinct functions.

The complex organization of

eukaryotic cells enables

them to carry out more

specialized functions than

prokaryotic cells.

What is a ribosome?

A cellular structure on

which proteins are made.

Inside the Eukaryotic Cell

Section 7-2

Key Idea: The

cytoskeleton helps the

cell move, keep its

shape and organize

parts.

An intricate network of protein

provides the interior framework

of the cell.

There are three types of

cytoskeleton fibers:

Microfilaments

Microtubules

Intermediate fibers

Key Idea: DNA instructions

are copied as RNA

messages, which leave the

nucleus. In the cytoplasm,

ribosomes use the RNA

messages to assemble

proteins.

The word assemble

means to fit

together parts or

pieces to build.

DNA is stored in the

nucleus.

Nuclear envelope

surrounds the nucleus.

Nucleolus is within the

nucleus where ribosome

parts are made.

Each ribosome in a cell is made of

RNA and many different proteins.

“free” ribosomes – suspended in the

cytosol, make proteins that remain

inside the cell.

“bound” ribosomes – attached to the

endoplasmic reticulum, make

proteins that are exported from the

cell.

What kind of protein do “free”

ribosomes make?

Proteins that remain in the

cell, such as proteins that

build new organelles or

enzymes to speed chemical

reactions.

Key Idea: The endoplasmic

reticulum and Golgi

apparatus are organelles

involved in preparing

proteins for extracellular

export.

A vesicle is a small, membrane-

bound sac that encloses the

protein and keeps them

separate from the rest of the

cytoplasm.

The endoplasmic reticulum is a

extensive system that moves

proteins and other substances.

The Golgi apparatus is a set of

flattened, membrane-bound

sacs.

Divided into 2 portions:

rough ER and smooth ER.

Rough ER has attached

ribosomes and makes

proteins

Smooth ER has no ribosomes

and makes lipids and breaks

down toxic substances.

The Golgi apparatus

helps modify, sort,

and package cell

products for

distribution.

Step 1: ER membrane pinches off and

forms a vesicle around the proteins.

Step 2: Vesicles transport the

proteins to the Golgi apparatus,

where they are modified by enzymes

and repackaged in new vesicles.

Step 3: New vesicles transport the

modified proteins to the cell

membrane to be released outside the

cell.

Key Idea: The vesicles help

maintain homeostasis by storing

and releasing a variety of

substances as the cell needs them.

A vacuole is a fluid-filled vesicle

found in the cytoplasm of many

plant cells.

Lysosomes contain

enzymes that recycle

old or damaged

organelles and digest

food particles to provide

nutrients for the cell.

A central vacuole helps

the cell become rigid,

allowing a plant to stand

up. When the vacuole

loses water, the cell

shrinks, and the plant

dies.

A contractile vacuole pumps excess

water out of the cell in order to

control the concentration of salts

and other substances.

A food vacuole is formed when the

cell membrane surrounds food

particles outside the cell and

pinches off to form a vesicle inside

the cell.

Key Idea: The energy for

cellular functions is

produced by chemical

reactions that occur in the

mitochondria and

chloroplasts.

The chloroplast is an

organelle found in plant and

algae cells that uses light

energy to make carbohydrates

from carbon dioxide and

water.

The mitochondrion is a cell

organelle that uses energy

from organic compounds to

make ATP.

They contain

chlorophyll which is a

green pigment that

helps with

photosynthesis.

Most of the ATP needed

by a cell is produced

inside mitochondria.

Both animal and plant

cells contain

mitochondria.

In what kinds of cells are

mitochondria found?

Nearly all eukaryotic cells,

including plant cells.

From Cell to Organism

Section 7-3

Key Idea: The different

organelles and features of cells

enable organisms to function in

unique ways in different

environments.

The flagellum is a long, hair-like

structure that grows out of the

cell and enables the cell to move

through its environment.

Prokaryotes can vary

in shape, the way

they obtain and use

energy, and their

ability to move.

Cell Structure Section 3

A

B

C

D

E

F

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Eukaryotic cells can vary

in shape and external

features and their internal

organelles.

Animal and plant cells are

two types of eukaryotic

cells.

Cell Structure Section 3

A

B

B

CD

DC

A

E

E

F

F

G

G

H

H

I

I

J

J

K

L

M

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What are flagella?

Long, threadlike structures

that rotate quickly to move

an organism through its

environment.

Key Idea: Plants and

animals have many highly

specialized cells that are

arranged into tissues,

organs, and organ

systems.

Cell Structure Section 3

Organization in Multicellular Organisms

Click to animate the image.

Tissue is a distinct group of

similar cells that perform a

common function.

An organ is a collection of

tissues that work together to

form a structure which performs

a specific function.

An organ system is composed of

a group of organs that work

together to perform major body

functions.

Muscle tissue is a group of

many cells that have

bundles of cytoskeleton

structures.

When the bundles

contract at the same time,

they help animals move.

The heart is an organ

made of muscle, nerve,

and other tissues.

Tissues work together

to pump blood.

The circulatory system is

made up of the heart, the

blood vessels, and blood.

In plants, the shoot

system consists of stems,

leaves, and the vascular

tissue that connects them.

Key Idea: A multicellular

organism is composed of

many individual,

permanently associated

cells that coordinate

their activities.

Colonial organism is a

collection of genetically

identical cells that are

permanently associated but

do not work together or

integrate cell activities.

Unicellular organisms

can thrive

independently or live

together in groups.

Example: slime molds

In a multicellular body,

cells are interdependent.

Distinct types of cells

have specialized functions

to help the organism

survive.

What is differentiation?

The process by which cells

of a multicellular organism

develop specialized forms

and functions.