Transcript Structure & Function

The Cell
Structure & Function
Dr. Childs
Science Computer Lab
Spring, 2004
Types of Cells
Two major groups of cells:
• Prokaryotes
• Eukaryotes
Prokaryotes
Prokaryotes are simple cells:
- Lack a membrane-bound nucleus
- Lack membrane-bound organelles
- Reproduce by binary fission
- Includes bacteria
Eukaryotes
Eukaryotes:
- Membrane-bound nucleus
- Membrane-bound organelles
- Reproduce by mitosis
- Includes fungi, plants, animals
Organelles
Eukaryotic cells contain membrane-bound
structures called “organelles”
Structure and Function
• Cells look like what they do!!
Nerve cells – transmit
electrical nerve impulses
Muscle cells – contractile fibers
Red blood cells – carry oxygen
in tiny blood vessels
White blood cells
Ingest & destroy bacteria
Protozoa – cilia for swimming
Eukaryotic Cell Structure
• Cell membrane
• Cytoplasm
• Nucleus
• Membrane-bound organelles
mitochondria
chloroplasts
• Endoplasmic reticulum with
ribosomes
Think of the cell as a factory!
Eukaryotic Cell Structure
nuclear membrane
nucleolus
mitochondria
nucleus
cell membrane
Nucleus
Chromatin
Nuclear pores
Nucleolus
Nuclear membrane
• Surrounded by a double nuclear membrane with pore.
• Chromatin is site of DNA – forms chromosomes.
• Prominent nucleolus – site of ribosome synthesis.
Factory – Nucleus is the control center. Blueprints in DNA.
Nucleus
chromatin – site of DNA
nuclear pore – allows passage of molecule
nuclear membrane - double membrane
nucleolus – produces ribosomes
rough endoplasmic reticulum
Note: during mitosis chromatin condenses to form
chromosomes
In a factory, the nucleus would be the control center and
contains blueprint in the form of DNA
Rough Endoplasmic Reticulum
rough endoplasmic reticulum
“rough ER”
Rough endoplasmic reticulum (or “rough
ER”) is the site of protein synthesis. These
are membranes lined with ribosomes. The
ribosomes look like “dots”.
In a factory, the rough ER would be the assembly line.
Ribosomes
Ribosomes
The “dots” on the rough ER are ribosomes.
Ribosomes are composed of a “large subunit”
and a “small subunit”.
Proteins are assembled on the ribosomes.
In a factory, the ribosomes are the machines on the
assembly line.
Golgi Complex
Golgi complex
• The Golgi complex is a series of flattened
membrane sacs. These complete final
protein assembly.
Secretory vesicles
• Proteins are “shipped” from the cell in
secretory vesicles (membrane-bound sacs).
In a factory, the Golgi complexes are the site
of final assembly and shipping.
Protein Synthesis
Proteins are synthesized on the
ribosomes on the rough ER.
Final synthesis is in the Golgi
complex.
Secretory vesicles carry proteins
to membrane, then out of the cell.
Lysosomes
lysosomes
Lysosomes contain digestive
enzymes.
Small spherical organelles with
single membranes with a dense
interior.
Site of intracellular digestion. Digests
food or foreign bodies as
bacteria.
In a factory, the lysomes are the “vacuum
cleaners” and recycling centers of the cells.
Mitochondria
Mitochondria are the site of energy
production. Energy is used for almost all
cellular functions.
Respiratory enzymes break down sugars
into high energy molecules.
Mitochondria have double membranes. The
inner membrane has finger-like “cristae”.
In a factory, the mitochondria are the “powerhouses”
of the cell.
Chloroplasts
Chloroplasts are the site of
photosynthesis and are unique to
plant cells.
Chloroplasts are green because of
the presence of chlorophyll, the
pigment that captures energy
from the sun
chloroplast
grana
The chlorophyll is located in the
membranes of “stacked coins” or
grana
Vacuoles
Plant cells have a large central
vacuole. This serves to store
water and nutrients as well as to
have maintain the rigid shape of
the cell.
central vacuole
Vacuoles
Contractile vacuoles occur in singlecelled protozoa.
contractile vacuole
These help pump out excess water.
Cell Membranes & Cell Walls
Both plant and animal cells have a cell
membrane that is bilaminate – it has two
layer.
In addition, plant cells have a rigid cell wall
composed of cellulose. This helps the
plant cell maintain their shape.
cell membrane
cell wall
Microtubules
Centrioles
Centrioles are usually located near one of
the poles of the cells. They are
composed of short sections of
microtubules.
Centrioles are only found in animal cells;
not in plant cells.
These have a role in mitosis (cell division)
Microtubules
Flagella & Cilia
Flagella and cilia are commonly found
in protozoa. Flagella are long and
few; cilia are short and many.
Cilia are also found in some animal
cells; for example, cells lining the
respiratory tract ciliated.
cilia
flagella
Flagella and cilia are composed of
microtubules.
microtubules
cross-section of flagellum