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Cell Structure and Transport
Biology Content Standards
2. Cell Biology
Broad Concept:
Cells have specific structures and functions that
make them distinctive. Processes in a cell can be classified broadly as
growth, maintenance, and reproduction.
2.1 Relate cell parts/organelles (plasma membrane, nuclear envelope,
nucleus, nucleolus, cytoplasm, mitochondrion, endoplasmic reticulum,
Golgi apparatus, lysosome, ribosome, vacuole, cell wall, chloroplast,
cytoskeleton, centriole, cilium, flagellum, pseudopod) to their functions.
Explain the role of cell membranes as a highly selective barrier
(diffusion, osmosis, facilitated diffusion, and active transport).
2.2 Compare and contrast, at the cellular level, prokaryotes and
eukaryotes (general structures and degrees of complexity).
2.8 Compare and contrast a virus and a cell in terms of genetic
material and reproduction.
Biology Content Standards
4. Anatomy and Physiology
Broad Concept: There is a relationship between the
organization of cells into tissues, and tissues into organs. The
structure and function of organs determine their
relationships within body systems of an organism.
Homeostasis allows the body to perform its normal functions.
4.7
Recognize that communication between cells is required
for coordination of body functions. The nerves communicate
with electrochemical signals; hormones circulate through the
blood, and some cells produce signals to communicate only
with nearby cells.
The Cell Theory
• All living things are composed of cells.
• Cells are the basic
units of structure/
function in living
things.
• All cells come from preexisting cells.
Key Scientists
• Anton van Leeuwenhoek
________________
• Robert Hooke
________________
• Robert Brown
________________
• Matthias Schleiden
________________
• Theodor Schwann
________________
• Rudolph Virchow
________________
Anton van Leeuwenhoek
Father of microscopy
Robert Hooke
Robert Brown
Coined the term “cell”
Discovered the nucleus
Robert Brown's Microscope
This instrument is preserved at the Linnaean Society in London.
This is the view Brown obtained in 1828, when he first
recognized the cell nucleus. It shows about twenty orchid
epidermal cells, and the nucleus can clearly be seen
within each cell. Three stomata can also be clearly seen these are the breathing pores through which a plant
exchanges gases with the atmosphere
Schleiden
“All plants are made of cells.”
Schwann
“All animals are made of cells.”
Rudolph Virchow
“All cells arise from the division of preexisting cells.”
Virchow rejected the ancient
idea that disease was an
affliction of the entire body.
“Disease, said Virchow, was
the result of a cellular
alteration”.
He made important
contributions to our
understanding of blood
coagulation, atherosclerosis,
leukemia, and other cancers.
Cell Structure
Cells come in many sizes and shapes!
Great Examples of Cell Structure-Function
• Ovum (Egg )
• Sperm cell
• Neuron
• Skeletal Muscle Cell
• Fat cell
• Leaf epidermis Cells
Ovum & Spermatozoa
Neuron
Skeletal Muscle Cells
Fat Cells
Leaf Epidermis
Protist - Amoeba
pseudopod
Bacteria - Anthrax
Prokaryotes vs. Eukaryotes
Prokaryotes
- Organisms that lack a nucleus
- Usually small and unicellular
-
Bacteria
Eukaryotes
Organisms whose cells contain a nucleus
and membrane-bound organelles..
Structures common to most Cells …
Cell Membrane
The membrane is like “the guard at the door!”
Cell Wall
• Supports and protects the cell
• Lies outside the cell membrane
• Pectin: gluey substance which holds plant cells
together: jelly
• Plants: cellulose
• Fungi: chitin
• Algae: varies…
• Some bacteria: peptidoglycan
Cell Wall
Primary cell wall:
composed of cellulose,
which provides elasticity
Secondary cell wall:
found in plants that
have woody stems 
cellulose + lignin
Cell Wall
(Pectin)
Nucleus
“Control center”
• Contains DNA, which, in eukaryotes, is attached
to special proteins forming chromosomes.
• Surrounded by 2 membranes, which form the
nuclear envelope. The nuclear envelope has
nuclear pores, which conduct traffic in and out.
• Nucleolus
- composed of RNA and proteins
- site of ribosome production
Nucleus
Nucleolus
DNA
Nuclear
Envelope
Nuclear
Pore
Nucleolus
Chromatin
Ribosomes
Proteins are made here!
Some are attached to membranes. Others are free in cytoplasm.
Cytoplasm
Cytosol (water with free-floating molecules) + organelles
Cell Organelles
Mitochondria
change the chemical
energy stored in food into
compounds that can be
used by the cell (ATP).
– 2 membranes
– Contain DNA
Cell Respiration takes place here!
Cristae
Matrix
Chloroplasts (plant cells and algae)
trap the energy of sunlight and convert it into chemical energy
(sugars and starches). Have 2 membranes. Contain DNA.
Photosynthesis takes place here!
Endoplasmic Reticulum (ER)
System of little tubes and sacs which
transports materials within the cell.
•
Rough Endoplasmic Reticulum (RER):
ribosomes stuck to its surface. Many proteins
that are released from the cell are made here.
•
Smooth Endoplasmic Reticulum (SER):
NOT covered with ribosomes. In some cells,
special enzymes and chemicals are stored
here.
Golgi Apparatus
Modifies, collects, packages, and distributes proteins
made at one location in the cell and used at another.
Lysosomes
• Membrane sac of enzymes formed by the Golgi
apparatus.
• Digest food and clean up/recycle
• Rarely found in plants
small food
particle
lysosomes
vacuole
digesting food
digesting broken
organelles
Vacuoles – sacs which store materials such as water, salts,
proteins, and carbohydrates.
Plant cells – single, large vacuole filled with liquid.
Plastids:
Plant organelles that come in a variety of forms.
Many store food and pigments.
• Chloroplasts …
• Leucoplasts – store starch granules.
• Chromoplasts – store pigment molecules.
Leucoplasts from Potato Cells
Chromoplasts from
Red Pepper Cells
Cytoskeleton
A network of
protein fibers in
the cytoplasm
that gives shape
to a cell, holds
and moves
organelles, and
is involved in
cell movement.
Types of Protein Fibers
Cilia and Flagella
Hair like organelles that
extend from the surface of the cell.
They help with movement.
Made of microtubules.
Cilia – short and present in large numbers.
Flagella – long and less numerous.
Euglena
Flagellum
Sperm
Flagellum
Cilia
Respiratory tract
A Protist
Centrioles
Found in most eukaryotic cells; absent
in higher plants and most fungi.
Nine triplets of microtubules
arranged in a very special way.
When two centrioles are found next to each other, they are
usually at right angles.
The centrioles are found in pairs and move towards
opposite ends of the nucleus when it is time for cell
division.
During division, centrioles create spindle fibers.
Plant
Cell
Levels
of
Organization
Cell Communication
• Direct cell-cell contact
Some cells can form gap junctions that
connect their cytoplasm to the cytoplasm
of adjacent cells. (Ex) cardiac muscle
• Neurotransmitters
Nerves communicate with electrochemical signals.
• Hormones
Hormones are produced by endocrine cells and
travel through the blood to reach all parts of the
body.
Cell Transport
Transport By Passive Processes
(No Energy Needed)
Diffusion - movement of molecules from a region of higher
concentration to one of lower concentration. Example: Aromas of
food. Oxygen and carbon dioxide pass easily through the cell
membrane because they can dissolve in lipids.
http://www.teachersdomain.org/asset/tdc02_int_membraneweb/
Rate of diffusion is a function of:
• Size and shape of the molecules
• Electric charges of the molecules
• Temperature and pressure
• Concentration gradient
Concentration gradient – the difference in concentration
of molecules of a substance from the highest to the lowest number of
molecules. Molecules of a substance that are moving from areas of
high concentration of that substance to areas of low concentration are
moving WITH the concentration gradient. The steeper the grade from
high to low, the more rapid the diffusion rate.
Transport By Passive Processes
(No Energy Needed)
Osmosis – diffusion of water through a selectively
permeable membrane. Water moves from high water
potential to low water potential.
The cell has NO CONTROL over osmosis!
Water will flow in and out of the cell until the
concentration is equal on each side of the membrane.
This is called EQUILIBRIUM.
Animal
Cells
Hypotonic
Cytolysis
Hypertonic
Crenation
To Review …
Cytolysis
No net movement of H2O
Crenation
Plant
Cells
Turgor Pressure
Plasmolysis
Cytolysis
Turgor pressure
No NET
movement
Crenation
Plasmolysis
Transport By Active Processes
Use of Carrier Molecules (PERMEASES) –
proteins in the cell membrane
1.
FACILITATED DIFFUSION – transport by
permeases down or with the concentration gradient.
Example = glucose transport
2.
ACTIVE TRANSPORT – transport by permeases
against the concentration gradient. The cell needs
ATP! Example = Na+ K+ pump
http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html
Facilitated Diffusion
Glucose
transport
Active Transport
Transport By Active Processes
Endocytosis – into the cell – needs ATP
1. Phagocytosis – cell-eating.
Example: amoeba using pseudopod !
2. Pinocytosis – cell drinking.
Exocytosis – out the cell – needs ATP
Endocytosis
Phagocytosis
The cell membrane pulls
in and pinches off placing
the solid particles in a
phagosome.
The phagosome then fuses
with a lysosome and the
material is broken down.
“Cell EATING”
Endocytosis
Pinocytosis
The cytoplasmic membrane
pulls in and pinches off
placing small droplets of
liquid in a pinocytic vesicle.
The liquid contents of the
vesicle is then slowly
transferred to the cytosol.
“Cell DRINKING”
Exocytosis
Endocytosis & Exocytosis
Receptor-Mediated Endocytosis
Endocytosis in which specific molecules become bound
to specific receptors on the cell surface and subsequently
enter the cytoplasm enclosed in special vesicles.
• Receptor-mediated endocytosis is used by animal cells to
take cholesterol up from the blood via low-density
lipoprotein (LDL) particles.
• The LDL receptor proteins are concentrated in depressed
regions of the membrane known as clathrin coated pits
because they are coated with a layer of a protein called
clathrin.
• After the LDL particle binds to the receptor protein, the
coated pit invaginates forming a coated vesicle.
LDL particles
bind to specific
LDL receptors
in coated pits of
the cytoplasmic
membrane.
The coat on the
inner surface of
the membrane is
a layer of a
protein called
clathrin.
A coated vesicle forms by endocytosis.
The clathrin
coating
detaches from
the vesicle and
is recycled
back to the
cytoplasmic
membrane.
The uncoated
vesicle is called
an endosome.
The endosome divides forming two vesicles.
One vesicle
recycles the
LDL receptor
proteins back to
the cytoplasmic
membrane.
The other
vesicle fuses
with lysosomes.
After the vesicle
fuses with the
lysosome, the
contents are
digested and free
cholesterol is
released into the
cytosol.
Viruses
How Big are Viruses?
What is a Virus?
Viruses are particles of nucleic acid, protein,
and in some cases lipids that can reproduce
ONLY by infecting living cells. They are NOT
living things!
Viruses differ widely in size and shape.
Viruses are usually classified based on their
genome. Retrovirus = RNA-based virus.
Viral Structure
A typical virus is composed of a core of either
DNA or RNA, surrounded by a protein coat, or
capsid.
Many animal viruses form an envelope around
the capsid. The envelope is rich in proteins, lipids,
and glycoproteins. Most of the envelope is from
the host cell’s membrane and serves as an
attachment site
Genome
•
DNA or RNA
• DNA - linear or circular,
double or single stranded
• RNA - single or double stranded
The protein coat, or capsid provides:
• protection
• attachment
• identity
• immunity
Viral Replication
• Lytic
• Lysogenic
Bacteriophage
Life Cycle of a Bacteriophage
Lytic
Replication
Lysogenic :
A host cell lives normally, but is harboring a
viral genome (prophage) within its own
genome.
Lysogenic