Chapter 2

The Cell

2-1 Cells: The Units of Life

The Microscope: A ToolQ: Why do scientists need to use

microscopes?

A: Cells are small

Before…

Compound Microscope

• Combines the power of 2 lenses to enlarge the image and blend light toward your eye

Eye piece lens X objective lens

10x X 4x Low power

10x X 10x

Medium Power

10x X 40x

High Power

= 40x

= 100x

= 400x

Eyepiece or ocular lens• Lens closest to the

eye

Objective Lens• Lens closest to the

specimen or object

Nosepiece• Objectives fastened

to this revolving structure

Stage• Where you place

your slide

Stage clips• Hold slide in place

Body Tube• Light travels through

here

Light Source• Provides light

Diaphragm• Regulates the light

reaching the objective lens

Base• Supports the

microscope

Arm• Holds the body

tube, acts as a handle

Coarse focusing knob• Used to focus under

low power only

Fine focusing knob• Used to focus under

high power only

A microscope reverses and inverts the image of an object seen under it

ee

Before viewing under the microscope

While viewing under the microscope

Things moving under a microscope are actually moving in the opposite direction

Things moving under a microscope are actually moving in the opposite direction

Stereoscopic light microscope

• Give you 3D view of an object

• Used to look at thick things light can’t pass through

Electron Microscopes• Can magnify

things more than 300,000 times

Transmission electron microscope

• Used to study parts inside a cell

Scanning Electron Microscope

• Used to see the surfaces of whole objects

Cell Theory1. All organisms are made up of

one or more cells

2. Cells are the basic units of structure and function in all organisms

3. All cells come from cells that already exist

2-2 Cell Structure

Living cells are dynamic and have several things in common

• Membrane

• Cytoplasm (gel-like material)

• Nucleus (control center)

There are 2 basic types of cells

1. Prokaryotic – no nucleus

2. Eukaryotic – has a nucleus

Cell Membrane• Structure that forms the outer

boundary of the cell and allows only certain materials to move in and out of the cell

Features of the cell membrane

• Flexible

• Double layer of fats with some proteins scattered throughout

Cytoplasm• Gel-like material inside the cell

membrane

Organelles• Structures within the cytoplasm of

eukaryotic cells

Nucleus• Structure that directs all the

activities of the cell

• Contains the DNA

Chromatin• Made up of protein and DNA

(genetic blue print)

Endoplasmic Reticulum• Folded membrane that moves

materials around in the cell

• Some have ribosomes on them, some don’t

Ribosomes• Make

proteins

• Some found on ER

• Others in cytoplasm

Golgi Bodies• The packaging and secreting

organelles of the cell

Mitochondria• Where food molecules are broken

down and energy is released

Lysosomes• Digests wastes

and worn out cell parts

Vacuoles• Storage areas, store water, food, wastes

• Small in animals and large in plants

Cell Wall• Rigid structure

outside the cell membrane that supports and protects the plant cell

Chloroplasts• Organelles where light energy is

changed into chemical energy in the form of a sugar called glucose (C6H12O6)

Chlorophyll• Chemical in chloroplasts that

traps light energy – reflects green light

Bacterial Cells• Prokaryotic

• Don’t have membrane – bound organelles

Features of bacterial cells

• Cell wall and cytoplasm

• Single chromosome

• No nuclei

• Ribosomes

2-3 Cell Organization

Nerve Cell• Send impulses

through your body

Red Blood Cells• Can change

shape

• Flexible

• Move through the duct work of your blood vessels

Plant Vessel Cell• Transports

water and minerals throughout the cell

Tissues• Groups of similar cells that do

similar things

• Ex.) smooth muscle tissue

Organ• A structure made up of different

types of tissues that work together

• Ex.) stomach

Organ System• A group of organs working

together to do a certain job

• Ex.) digestive system