CHAPTER 6 - CELLS

Section 6.1 & 6.2

Importance of cells

An organism’s basic unit of structure & function is the cell

Everything we do occurs fundamentally at the cellular level Thinking Moving Maintaining homeostasis

Cells discovered by Robert Hooke in 1665

Studying Cells

How do we understand cells if we can’t see them?

Microscopes allow us to see the inner workings of cells

Two main types of Microscopes Light Microscope (LM) – 1665-present Electron Microscope (EM) – 1950’s-present

Light Microscopes

Allow us to see plant & animal cells and the nucleus.

Can also see bacteria cells. Light passes through the specimen and

lenses, bends the light to magnify the image.

Magnification: ratio of an object’s image to its real size (max. about 1,000x)

Resolution: measure of the clarity of the image (max. about 200nm – size of bacteria)

Electron Microscopes

Rapidly advance our understanding of cells because we could see subcellular structures

Focuses a beam of electrons through the specimen

Two types: Scanning electron microscope (SEM)

Gives a 3D image of the surface of the specimen Transmission electron microscope (TEM)

Used to study internal stux – gives a cross section

Advantages & Disadvantages Light Microscopes

Advantage: Can study living organisms Disadvantage: Can’t see organelles in

detail Electron Microscopes

Advantage: Can see organelles in detail Disadvantage: Specimens are killed in

preparation process (not for living tissues)

Cell Fractionation

Goal: take cells apart and separate the major organelles from one another

Process: Centrifuge spins test tubes at various

speeds Cell components separate by size and

density Result:

Bulk quantity of cellular organelles to study composition and function

Section 6.2

Two types of cells Prokaryotic found in Domain _______ & _______ Eukaryotic found in Domain _______

What 4 Kingdoms contain organisms with Eukaryotic cells?

1. Animal 2. Plant 3. Protist 4. Fungi

Similarities & Differences

All Cells contain: Plasma membrane made up of a __________

Phospholipid bilayer Cytosol (cytoplasm) DNA Ribosomes

Differences: Eukaryotic cells contain membrane bound

organelles and the DNA is contained in the nucleus.

Prokaryotic cells:

DNA located in nucleoid region Prefix: pro means “before” Suffix: karyon means “kernel” (nucleus) No membrane bound organelles in

cytoplasm Smaller & simpler Cilia and flagella for locomotion Some have cell wall surrounding plasma

membrane

Prokaryotic cells

Cell Size

Cellular metabolism sets a limit on how large a cell can get

The cell needs to bring in oxygen & nutrients and needs to get rid of waste

Cell needs to maintain a high surface area to volume ratio to exchange the materials it needs to

Larger organisms do not have larger cells just more of them (we have trillions of cells!)

Surface area to volume ratio

Plasma membrane

Eukaryotic cells

Contain membrane bound organelles Larger than prokaryotic cells and more

complex Animal & Plant cells Draw a diagram of an animal and a plant

cell