life science chapter 2 the cell
TRANSCRIPT
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