Cell Structure
& Function
http://koning.ecsu.ctstateu.edu/cell/cell.html
Cytology-Study of Cell Biology
Definition of Cell
A cell is the smallest unit that is
capable of performing life
functions.
The Cell
• A cell is the smallest unit of living
matter.
• Don’t confuse this with: atom,
element, proton, etc.
Cell Structure
• Relies on 4 critical properties
– Matter
– Energy
– Organization
– Information
Matter
• Matter found in living matter is composed
of elements, molecules, and
macromolecules
• Life (cells) depend on organic molecules
• Cells are composed of the same
macromolecules—carbohydrates, lipids,
proteins, nucleic acids.
• These compounds are composed of 6
main elements. C H O N P S
Energy
• Needed to carryout life processes
– Build molecules and
macromolecules(synthesis)
– Break down macromolecules and molecules
– To carryout cell functions
– To overcome disorder , to maintain
organization
– Energy molecule the cell uses is
ATP adenosine triphosphate
Organization
• Cells are not a haphazard bag of
components
• Molecules and macromolecules that make
up cells have specific sites where they are
found.
InformationCell organization requires instructions
• Genetic materials that carries the instructions
• Genome- the entire complement of its genetic
material
• Every living cell has a copy of its genome
• Genome contains the genes that carry the
information to create cells with particular
structures and functions.
Cell Theory
• “Theory” is not a casual term in science.
• Tested innumerable times with consistent
results.
• Universally accepted
• One of the most basic, fundamental
concepts in the foundation of biology.
Cell Theory 1800’s
1. Matthias Schleiden- GermanBotanist
Studied plant material
Saw compartments with dark areas
Cells are living entities and plants are
aggregates of cells
2. Theodor Schwann-German physiologist
friend of Schleiden
He saw similar compartments and large
numbers nuclei in animal tissues.
Schwann extended Schleiden’s hypothesis to animals.
3.Rudolf Virchow-German Biologist
Research diseased cells-discovered that “every cell originate from
another cell”
Cell Theory
• All organism are made of cells.
• Cells are the smallest structural and
functional units of organisms
• All cells come from pre-existing cells
• Cells are capable of self-reproduction by
cell division.
Cell Size-Cells are small
Types of Organisms based on
number of cells
• Unicellular organisms
– Bacteria, Protists, etc.
• Multicellular organisms
– Protist
– Fungi
– Plants
– Animals
• Muscles, skin, nerves, liver, digestive, bones,
blood, immune system, lungs, etc.
Two Types of Organism
based on Cell Structures
•Prokaryotes- organisms that have
prokaryotic cells- cells that do not have a
nucleus or organelles
•Eukaryotes-organism that have eukaryotic
cells-cells that have a nucleus and
structures called organelles that carryout
specific functions.
All Cells have the following
1. Plasma membrane-Maintains
Homeostasis
Structure--Made of 2 layers (bilayer) of phospholipids
and embedded proteins, can give some cells their
shape
Insoluble in water
Main Function-Maintain Homeostasis by:
Forms a barrier between the cell’s internal environment
and the external environment
Semipermeable-controls movement of material into and
out of cell
Communicates with other cell membranes and
molecules in the external environment
2. Cytoplasm
• Region of the cell that is contained within
the plasma membrane
• Fluid within the cell that contains water
and molecules
3. Ribosomes
• Made of RNA molecules Ribonucleic Acid
• Function- place where polypeptides and
protein are synthesize (produced)
• Free Ribosomes are found in cytoplasm of
both prokaryotic and eukaryotic cells
• Bound Ribosomes are found on rough
Endoplasmic reticulum in eukaryotic cells
4.Genetic Material-DNA
• Prokaryotic Cells-DNA is found in the
central part of cytoplasm called the
nucleoid region
• Eukaryotic Cells-DNA is found inside the
Nucleus
DNA in the two cell types is precisely the
same kind of DNA, and the genetic code is
exactly the same
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
Prokaryotic Cell
• Do not organelles-structures surrounded
by membranes
• Few internal
structures
• One-celled
organisms,
• Bacteria
http://library.thinkquest.org/C004535/prokaryotic_cells.html
Prokaryotic Cells
• Small, less complexity
• all materials within the cell are relatively
close together
• Prokaryotic cells have no nucleus.
• DNA is circular (it has no ends) and is
found in nucleoid region is essentially an
imaginary "structure." There is no physical
boundary enclosing the nucleoid.
Prokaryotic Cells
• Prokaryotic ribosomes are small and
composed of only three kinds of rRNA and
about fifty kinds of protein.
• contains no membrane-bound
organelles.
Basic Prokaryotic Cell
Capsule or Slime layer
Some bacteria
Surrounds the cell wall and
plasma membrane
Made up of polysaccharides .
Function
Traps water to keep the
bacterium from drying out and
to protect it from phagocytosis
(engulfing) by larger
microorganisms.
More Structures
Cell Wall• rigid structure outside the plasma
membrane.
Functions
• It supports and protects the plasma
membrane.
• It is permeable and will allow material to
reach the plasma membrane.
More Structures
• Pili - Many species of bacteria have pili (singular, pilus), small
hairlike projections emerging from the outside cell surface.
• These outgrowths assist the bacteria in attaching to other cells and
surfaces, such as teeth, intestines, and rocks. Without pili, many
disease-causing bacteria lose their ability to infect because they're
unable to attach to host tissue.
• Flagella - Flagella (singular, flagellum) are hairlike structures
that provide a means of locomotion for those bacteria that have
them. They can be found at either or both ends of a bacterium or all
over its surface. The flagella beat in a propeller-like motion to help
the bacterium move toward nutrients; away from toxic chemicals; or,
in the case of the photosynthetic cyanobacteria; toward the light.
Eukaryotic
• Contain organelles small structures surrounded by
membranes that perform specific functions
• All other organisms except Bacteria
Plant
http://library.thinkquest.org/C004535/eukaryotic_cells.html
Animal
“Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
“Typical” Plant Cell
http://waynesword.palomar.edu/images/plant3.gif
Surrounding the Cell
Cell Membrane
• Outer membrane of cell
that controls movement
in and out of the cell
• Double layer of
phospholipids (bilayer)
• Animal (Blue #1)
• Plant (Blue #4)
http://library.thinkquest.org/12413/structures.html
Cell Wall
• Most commonly
found in plant cells
& bacteria
• Made of
carbohydratescellulose in plants
• Not found in animal
cells
• Supports & protects
cells
• Plant Cell (Red #2.3)
http://library.thinkquest.org/12413/structures.html
Cells walls are in plant cells not animal cells
Inside the Cell
Eukaryotic Cell
Part I. Cytosol
Occupies about 50 % of volume
Site of many chemical reactions-Metabolism
1. Main Structure is Cytoskeleton
1.Microfilaments
2. Microtubules
3. Cilia
4. Flagellum
Part II Nucleus
Nucleus
• Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material - DNA
Nucleus: DNA stored here.
The Control Center Nuclear
envelope:
membrane
surrounding the
nucleus
Nuclear pores:
open portals of
communication
between the
nucleus &
cytoplasm
Chromatin:
condensed
DNA
Chromosome:
very tightly
packed DNA
Nucleolus:
dense region of
chromatin
Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
http://library.thinkquest.org/12413/structures.html
Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings allow
material to enter and
leave nucleus
http://library.thinkquest.org/12413/structures.html
Chromosomes
• In nucleus
• Made of DNA
• Contain instructions
for traits &
characteristics
http://library.thinkquest.org/12413/structures.html
Part III Endomembrane System
• Network of membranes and organelles
where molecules are produced and
modified and transported in and out of cell
Endoplasmic Reticulum
• Interconnected highway
within the cell
• Moves materials around
in cell
• Smooth type: lacks
ribosomes
• Rough type (pictured):
ribosomes embedded in
surface
http://library.thinkquest.org/12413/structures.html
Ribosomes: protein factories
Rough ER: make proteins (studded with ribosomes)
Smooth ER: make lipids, modify proteins made in RER
Golgi Bodies
• Protein processing,
modifications and
repackaging
organelle
• Called Golgi complex
or apparatus also
http://library.thinkquest.org/12413/structures.html
1-receives proteins & lipids in membrane-bound vesicles from ER.
2-modifies those proteins & lipids.
3-sorts and ships the proteins & lipids away in membrane-bound
vesicles.
Lysosome
• Digest cell parts and waste
• Contains many digestive
enzymes
• Break down proteins, fats,
and carbohydrates and
waste products
• Transports undigested
material to cell membrane
for removal
• Cell breaks down and is
digested if lysosome
membrane is broken
• Animal development
http://library.thinkquest.org/12413/structures.html
Vacuoles
• Membrane-bound sacs
for storage,
• Stores water, waste,
toxins,
• Stores enzymes for
digestion, and waste
removal
• Contains fluid (water
and molecules
• Help plants maintain
shape (central vacuole)
http://library.thinkquest.org/12413/structures.html
Central Vacuole-takes up much of plant cell volume
Tonoplast is the
membrane around
the central vacuole
Central vacuole
stores water, salts,
organic compounds
etc. for the plant
cell
The pressure inside
the vacuole builds
up and enables
plant cells to
support omplex
structure such as
leaves and flowers
Vacuoles and vesicles are storage organelles in cells. Vacuoles are larger
than vesicles. Either structure may store water, waste products, food, and other
cellular materials. In plant cells, the vacuole may take up most of the cell's
volume.
The membrane surrounding the plant cell vacuole is called the tonoplast.
Video of Paramecium contractile vacuole
http://www.youtube.com/watch?v=4z98WI
eNtjM
Part IV Semiautonomous
Organelles
• These organelles can grow and divide to
reproduce themselves
• But still depend on other parts of the cell
Mitochondria
• Small, can be few hundred to
thousands.
• Cell needing a lot of energy will have
thousands
• Cellular Respiration – changes
chemical energy ( fats &
carbohydrates) into a energy
molecule(ATP)
• ATP is what cell used to do work
• Controls level of water and other
materials in cell
• Recycles and decomposes proteins,
fats, and carbohydrates
http://library.thinkquest.org/12413/structures.html
Contains
Maternal DNA
Chloroplast-site of
Photosynthesis
• Only found in plant cells and other
photosynthetic cells
• Never found in animal cells
Chloroplast
• Contain there own
DNA
• Contains green
chlorophyll pigment
• Where
photosynthesis takes
place
• Converting Inorganic
compounds into sugar
using sun’s energy
http://library.thinkquest.org/12413/structures.html
Not found in animal cells
Peroxisomes
• Catalyze certain chemical reactions
• Breaks down molecules by removing
hydrogen or adding oxygen
• Liver cells have many peroxisomes
– Toxins in the liver cells are broken down and
release hydrogen peroxide- a lethal toxin to
cells.
– Catalase enzyme breaks hydrogen peroxide
into water and oxygen gas