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BIOLOGY CHAPTER 7, SECTIONS 1-2
CHAPTER 7 - CELL STRUCTURE AND
FUNCTION
(modified from PowerPoint by Mrs. Fisch)
SECTION 1: LIFE IS CELLULAR
Anton van Leeuwenhoek
• Observed tiny living
organisms in pond
water using a
microscope
• one of the first to use
a microscope to study
nature
•
•
Robert Hooke
1665 - Used
microscope to look
at thin slices of cork
(plant tissue)
Saw thousands of
tiny chambers and
called them cells
Mathias Schleiden – concluded that all
plants are made of cells (1838)
Onion skin cells
Theodor Schwann – all animals are
made of cells (1839).
Human red blood cells
Rudolf Virchow – new cells are
produced from the division of preexisting cells (1855).
Cell Theory
1. All living things are composed of
cells.
2. Cells are the basic units of structure
and function in living things.
3. New cells are produced from existing
cells.
All cells today represent a continuous
line of descent from the first living cells.
http://www.youtube.com/watch?v=4OpBylwH9DU
Cell size is limited.
As cell size increases, it takes longer
for material to diffuse from the cell
membrane to the interior of the cell.
Surface area-to-volume ratio: as a
cell increases in size, the volume
increases faster than the surface area
7
How big are cells?
• Microscopic (mostly)
• Measured in µm (micrometers) (also
known as “microns”).
All cells:
• Are surrounded by a barrier called the
cell membrane
• Contain DNA at some point in their life
Two categories of cells, depending on if
they have a nucleus:
• Prokaryotes
• Eukaryotes
Prokaryotes
before
1.
2.
3.
4.
5.
kernel, nucleus
NO nucleus
NO membrane bound organelles
ALL are unicellular
Smaller than eukaryotic cells
Forerunner to eukaryotic cells
(smaller and simpler)
6. DNA – circular
7. Ex: ALL bacteria
Flagella (plural; singular = flagellum)
- present in some prokaryotic cells
- whip-like tail used for locomotion
Eukaryotes
true
nucleus
1. Have a nucleus with a nuclear envelope
2. Bigger and more complex than
prokaryotes
3. Have membrane bound organelles
(Golgi, ER, lysosomes, etc.)
4. DNA – forms chromosomes (highly
organized)
5. Can be uni- OR multicellular organisms
6. Ex: animals, plants, fungi
Similarities - Prokaryote and Eukaryote
• Contain all four biomolecules (lipids,
carbohydrates, proteins, and nucleic
acids)
• Have ribosomes
• Have DNA
• Similar metabolism
• Can be unicellular
• Have cell membranes
1. Which type of organisms contain a
nucleus?
2. What does the Latin word karyon
mean? What cell structure does this
describe?
3. What type of organisms are
bacteria?
4. What protective barrier do both
prokaryotes and eukaryotes have in
common?
5. What is a whip-like tail used for
locomotion in some prokaryotes?
6. What type of cells do plants have?
SECTION 2: EUKARYOTIC CELL
STRUCTURE
Organelles – specialized “little
organs” within cells
Cytoplasm - viscous fluid containing
organelles
Contains:
• interconnected filaments and
fibers (cytoskeleton)
• fluid = cytosol
• organelles
• storage substances
Cytoskeleton – network of protein
filaments that helps cell maintain
shape, aids in movement and anchors
organelles
Three fiber types that form cytoskeleton:
–Microfilaments – thin, stringy for
structure and movement
–Microtubules – round, tubular
• Ex:
–centrioles – for cell division
–cilia – hair-like projections for
movement
–flagella
–Intermediate filaments
Nucleus – control center of cell.
• Surrounded by
nuclear membrane
(nuclear envelope)
• Contains
–DNA
–chromatin
–chromosomes
–nucleolus
Nuclear membrane
(nuclear envelope)
• Separates nucleus from
rest of cell
• Double membrane
• Has nuclear pores – control
what goes in and out of
nucleus
DNA - hereditary material
• Chromatin – granular
(having grains or particles)
material that contains DNA
bound to proteins
• Chromosomes – condensed
chromatin. Become visible
during cell division.
Nucleolus - small dense region in
nucleus where ribosomes are
assembled
RIBOSOMES - particles of RNA
and protein that have the main
function of assembling proteins.
• Found throughout the
cytoplasm or attached
to the endoplasmic
reticulum
Endoplasmic Reticulum (ER) network of interconnected
membranes that helps move things
within the cell.
• Synthesizes proteins and lipids for
cell membrane
• Two types:
–Rough endoplasmic reticulum
–Smooth endoplasmic reticulum
Rough Endoplasmic Reticulum
• Ribosomes attached to surface
• May modify proteins from
ribosomes
Smooth Endoplasmic Reticulum
• No attached ribosomes
• Has enzymes that help build
molecules
–Carbohydrates
–Lipids
Golgi Apparatus - modifies, sorts and
packages proteins from ER for storage
or export (in packages of membranes
called “vesicles”)
Lysosomes
• Contain digestive enzymes
• Functions:
–Break down lipids, carbohydrates,
and proteins into smaller units for
use in cell.
–Break down old cell parts
–Clean up cell “junk”
Vacuoles - membrane-bound sacs
used for storage
• More common in plants than animals
–large central vacuole stores water
–exerts pressure against wall,
making cell rigid
Mitochondria (plural; singular = mitochondrion)
– powerhouses of cell. Convert
chemical energy from food into a
compound (ATP) for cell to use for
energy.
• Have their own DNA
• Bound by double
membrane
• Most are passed on
in cytoplasm of egg
cell.
Chloroplasts - capture energy from
sunlight and convert it to chemical
energy that the cell can use.
•
•
•
•
Where photosynthesis takes place
Only in plant cells
Surrounded by two membranes
Contain chlorophyll – green
pigment
Chloroplasts
Endosymbiotic Theory – theory that
mitochondria and chloroplasts
evolved from prokaryotes
• Both contain DNA
• Both surrounded by two membranes
1. What is the granular material in the
nucleus that contains DNA?
2. What is the covering of the nucleus
called?
3. What is the center of the nucleus
where ribosomes are assembled?
4. Which cellular structure is used for
storage?
5. Which cellular structure is used for
cleaning up dead things within the
cell?
6. What is the “powerhouse” of the
cell?