Download Chapter 7 - Holden R

Chapter 7
A View of the Cell
7.1 Microscopes

Compound light microscopes
• Use a series of lenses to magnify objects
• Can magnify up to 1500 times
• Uses a beam of light

Electron Microscopes
•
•
•
•
Uses a beam of electrons to magnify objects
Can magnify up to 500,000 times
Specimens must be examined in a vacuum
Two types:
Scanning electron microscope scans the surface
of cells to view the 3 dimensional shape
 Transmission electron microscopes allow
scientists to study structures in a cell

7.1 Cell Theory

With the invention of microscopes,
scientists were able to conduct more
in-depth investigations and created
the cell theory, which has 3 basic
ideas:
• All organisms are composed of one or
more cells
• The cell is the basic unit of structure
and organization of organisms
• All cells come from cells that already
existed
7.1 Types of cells

There are 2 basic types of cells
• Prokaryotes
Do not have membrane bound organelles
 Include most single celled organisms

• Eukaryotes
Have membrane bound organelles
 Includes most multi celled organisms
 Have a nucleus, which manages and
controls cellular functions


Organelles each have a specific
function within the cell
7.1 Prokaryotic cells

Prokaryotic cells have the following
structures:
• Cell wall
• Plasma membrane
• Ribosomes
• DNA
• Cytoplasm
7.1 Eukaryotic Cells

Eukaryotic Cells contain the following
structures:
• Plasma membrane
• Cytoplasm
• Chromosomes
• Nucleus
• Nucleolus
• Organelles
7.2 Plasma Membrane

The plasma membrane is the flexible
boundary between the cell and its
environment
• It allows nutrients to enter and exit the
cells
• It allows waste to exit the cell
• It is described as being selectively
permeable, because it lets some things
through but not others

It can also change what it allows to pass
through at different times
7.2 Plasma Membrane Structure

The plasma membrane is made of a
phospholipid bilayer, which is composed of
2 layers of phospholipids back to back
• Phospholipids are composed of a glycerol
backbone, 2 fatty acids chains and a
phosphate group

The fatty acid tails are non-polar
• These are on the inside of the bilayer

The phosphate head is polar
• This is on the outside of the bilayer
7.2 Fluid Mosaic Model

The model of the plasma membrane
is called the fluid mosaic model
• Fluid because the phospholipids move
within the membrane (similar to water
waves moving in a lake)
• Mosaic because proteins create a
pattern on the surface of the bilayer
7.2 Other components

Cholesterol
• Stabilizes the phospholipids by
preventing their fatty acid tails from
sticking together
• Cholesterol can be harmful in large
quantities, but some is necessary for
this purpose

Transport proteins
• Regulate which substances enter and
leave the cells
7.3 Cell Structures

Eukaryotic Cells are divided into 2
categories: plant cells and animal
cells
• Animal cell structures include a plasma
membrane, ribosomes, a cytoskeleton,
an endoplasmic reticulum, a golgi
apparatus, lysosomes (some cells),
mitochondrion, a nucleus, a nucleolus,
and vacuoles (some animal cells)
• Plant cells include these items plus a cell
wall and chloroplasts
7.3 Cell Parts & Functions I




Plasma membrane- flexible cell boundary
that is selectively permeable
Cell wall- rigid cell boundary outside the
plasma membrane that provides additional
structural support
Nucleus- controls organelle activity and
includes directions to make proteins in the
DNA, which is in a stringy form called
chromatin
Nucleolus- inside the nucleus-makes
ribosomes
7.3 Cell Parts & Functions II
Ribosomes- where cells produce
proteins according to the directions
in DNA
 Cytoplasm-clear gelatinous fluid
inside a cell-suspends organelles
 Endoplasmic reticulum (ER)- site of
cellular chemical reactions

• Rough ER has ribosomes
• Smooth ER does not have ribosomes
7.3 Cell Parts & Functions III



Golgi Apparatus- modifies proteins by
sorting and packaging them and sending
them to the correct location
Vacuoles- temporary storage of materials
(food, enzymes, waste)
Lysosomes- contain digestive enzymes
that digest extra or worn out organelles,
food, and viruses/bacteria
• They can fuse with vacuoles to empty their
contents
7.3 Cell Parts & Functions IV


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Chloroplasts- trap light energy and
convert it to chemical energy; contain
chlorophyll a green pigment that traps
light energy
Mitochondria- transform energy for the
cell
Cytoskeleton- a network of rods
(microtubules) and filaments
(microflaments) inside the plasma
membrane that provide structure and
maintain the shape of the cell
7.3 Cell Parts & Function V
Centrioles- play a role in cell division
 Cilia- short numerous projections
that look like hairs that allow the cell
to move
 Flagella-long projections (1 or 2 per
cell) that allow the cell to move
 Nuclear membrane- separates the
cytoplasm from the nucleus

7.3 Animal Cell
Plasma
membrane
lysosome
Golgi
Apparatus
centriole
nucleolus
mitochondria
Endoplasmic
reticulum
vacuole
nucleus
cytoplasm
ribosomes
Nuclear membrane
7.3 Plant Cell
Nuclear membrane
Cell
wall
mitochondria
cytoplasm
nucleus
nucleolus
ribosomes
Endoplasmic
reticulum
Golgi apparatus
Plasma
membrane
Vacuole
chloroplast
cytoskeleton