Post on 04-Apr-2018
Reference: Chapter 2
A Tour of the Cell reference: Chapter 6
1
Monkey Fibroblast Cells stained with fluorescent dyes to show the nucleus
(blue) and cytoskeleton (yellow and red fibers), image courtesy of Nikon
Instruments & Florida State University
Overview & Objectives
v Outline § Basic Features of Cells § Animal Cell Structures
v Objectives § List the major structures that make up animal cells and describe
their functions § Be able to recognize and label organelles and other cell structures
in a picture of a cell
v Important concepts: § Cells are the building blocks of all life § Cells are the smallest living things § Cells arise only from other cells
Cells
v Living organisms are either § Prokaryotes
§ Single-celled organisms that lack specialized internal structures, such as a nucleus
§ e.g. bacteria
§ Eukaryotes § Organisms whose cells contains a nucleus
and other complex internal structures
§ May be single-celled (e.g. protozoa such as amoebae
§ Multi-celled, such as plants and animals (and you!)
THE MICROSCOPIC WORLD OF CELLS v Scale:
§ mm = millimeter = one thousandth of a meter (small; barely see it) § µm = micrometer = one millionth of a meter (really small; can’t see it)
§ nm = nanometer = one billionth of a meter (really, really really small)
Cell Structures
v All cells consist of two basic components: § Plasma Membrane (aka Cell Membrane)
§ This encloses the contents of the cell and regulates the passage of materials into and out of the cell
§ Cytoplasm § Internal contents of the cell
v Many cells also possess an Extracellular Matrix § Material that forms a coating around the cell § Holds cells together in tissues; can also be the starting material for
bone and other structures
Cell Structures: The Plasma Membrane
v Separates the living cell (cytoplasm) from its nonliving surroundings
v The membranes of cells are composed of macromolecules § Lipids § Proteins § Carbohydrate
Cell Structures: The Plasma Membrane
v The lipids belong to a special category called phospholipids § Glycerol backbone § Two hydrophobic fatty
acid “tails” § Hydrophilic phosphate
“head” § Organic group (R)
sometimes attached to phosphate § proteins § carbohydrates
Cell Structures: The Plasma Membrane
v Phospholipids form a two-layered membrane, the phospholipid bilayer
v This thin, flexible bilayer surrounds the cell contents and prevents most materials from entering or leaving the cell
Outside cell
Cytoplasm (inside cell)
(a) Phospholipid bilayer of membrane
Cell Structures: The Plasma Membrane v Carbohydrate chains attach to the proteins and lipids in
the plasma membrane § Important in cell-cell recognition
Cell Structures: The Cytoplasm
v A semi-fluid matrix that fills the interior of the cell v Most cellular activities occur in the cytoplasm
§ Highly organized § Consists of 3 components
1. Cytosol § Gooey liquid; makes up about 80% of the cell § Composed of water, salts, organic molecules
2. Organelles § “Little organs”; specialized structures in the
cytoplasm 3. Vesicles
§ Membrane-bound sacks that transport materials and carry out chemical reactions within the cell
Cell Organelles: The Nucleus v The nucleus is the “manager” of the cell
§ Contains chromatin (DNA) that carries the genes which code for proteins
§ Bordered by a double membrane called the nuclear envelope
§ Also contains the nucleolus, a region of the nucleus where ribosomes are assembled
Cell Organelles: Ribosomes
v Ribosomes are small organelles § Mixture of protein and RNA (ribonucleic acid) § synthesize the cell’s proteins
Cell Organelles: The Endomembrane System
v Many of the membranous organelles in the cell belong to the endomembrane system § They manufacture and
distribute cell products
v Four components: 1. Rough Endoplasmic
Reticulum (RER) 2. Smooth Endoplasmic
Reticulum (SER) 3. Golgi Apparatus 4. Lysosomes
The Endoplasmic Reticulum
v The endoplasmic reticulum (ER)
§ Produces an enormous variety of molecules
§ Is composed of smooth and rough ER
Nuclear envelope
Ribosomes
Rough ER Smooth ER
1. Rough Endoplasmic Reticulum, RER
v “Roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane
v The functions of the RER include: § Producing proteins § Producing new membrane
RER
1. Rough Endoplasmic Reticulum, RER
v After the rough ER synthesizes a molecule it packages the molecule into transport vesicles
Transport vesicle buds off
Ribosome Secretory protein inside transport vesicle
Protein Rough ER
Polypeptide
1 2
3
4
2. Smooth Endoplasmic Reticulum, SER
v SER lacks the surface ribosomes of RER § Produces a different
variety of compounds, such as lipids, including steroids
SER
3. The Golgi Apparatus
v Golgi works in partnership with the ER § Refines, stores, and distributes the products of cells
§ The “UPS Store” of the cell § Consists of flattened membranous “sacks” § Vesicles fuse and pinch off from the sacks
Transport vesicle from ER
“Receiving” side of Golgi apparatus
Golgi apparatus
New vesicle forming
Transport vesicle from the Golgi
“Shipping” side of Golgi apparatus
Plasma membrane
4. Lysosomes
v A lysosome is a membrane-enclosed sack § contains digestive enzymes § Lysosomes have 2 functions:
1. fuse with food vacuoles to digest food
4. Lysosomes
2. break down damaged organelles
• Visual Summary: The Endomembrane System
Cell Organelles: Mitochondria
v Cells require a constant energy supply to carry out the work of life
v Cells use a chemical form of energy known as ATP (adenosine triphosphate)
v Mitochondria are “Powerplants” that supply the cell’s energy needs by producing ATP
v Production of ATP is known as Cellular Respiration
mitochondria
Cell Structures: The Cytoskeleton
v The cytoskeleton is the infrastructure of the cell v Consists of a network of protein fibers v Controls cell shape and movement
Flagella and Cilia
v Cilia and flagella are external appendages
v Flagella propel the cell in a whiplike motion
§ Useful when you need to get somewhere in a hurry, like the sperm cell shown below
Flagella and Cilia
v Cilia are smaller than flagella § Usually occur rows along the surface of the cell § Beat in a coordinated fashion for locomotion or to move particles
toward or away from the cell
v The ciliates are a group of single-celled protists that have cilia covering the entire body
v Small animals like rotifers use cilia to gather food
Flagella and Cilia
v More structurally complex animals often have ciliated cells within their bodies
v The human windpipe is lined with cilia, as is the lining of the female reproductive tract
v In the windpipe, the cilia beat in unison to propel dust and mucus out of the lungs
A Panoramic View of Eukaryotic Cells
Summary: Prokaryotic Cells Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Cell wall
Capsule
Flagella A typical
rod-shaped bacterium
(a)
Bacterial chromosome
0.5 µm
A thin section through the bacterium Bacillus
coagulans (TEM)
(b)
v Prokaryotic cells are characterized by having § No nucleus § DNA in an unbound region called the nucleoid § No membrane-bound organelles § Cytoplasm bound by the plasma membrane
Summary: Prokaryotic Cells
v Eukaryotic cells are characterized by having § DNA in a nucleus that is bounded by a membranous
nuclear envelope § Membrane-bound organelles § Cytoplasm in the region between the plasma
membrane and nucleus
v Eukaryotic cells are generally much larger than prokaryotic cells
Summary: Eukaryotic Cells
Summary: Eukaryotic Cells
(Animal) Flagellum
Centrosome
CYTOSKELETON: Microfilaments
Intermediate filaments Microtubules
Microvilli
Peroxisome
Mitochondrion Lysosome
Golgi apparatus
Ribosomes
Plasma membrane
Nuclear envelope
Nucleolus
Chromatin
NUCLEUS
ENDOPLASMIC RETICULUM (ER)
Rough ER Smooth ER
Plant cells are also Eukaryotic, but have a few unique features… NUCLEUS
Nuclear envelope
Nucleolus Chromatin Rough ER
Smooth ER
Ribosomes
Central vacuole Microfilaments Microtubules
CYTOSKELETON
Chloroplast
Plasmodesmata Wall of adjacent cell
Cell wall
Plasma membrane
Peroxisome Mitochondrion
Golgi apparatus