Transcript Cell - Structure & Function

Cell - Structure &
Function
Unit #3
Generalized Cell
• Cellular level is
where living
processes occur.
• Disease processes
occur at the cell
level.
Cancer cells
Cytology
• Or cellular
biology, is the
study of
cellular
structure and
function.
Ciliated columnar epithelial cells
Generalized Cell
• Cells are divided
into three basic
parts:
• Plasma (cell)
membrane
• Cytosol (jelly-like
fluid within the
cell)
• Organelles
Generalized Cell
Plasma membrane
– Separates the cell’s
internal
environment from
its external
environment
(interstitial fluid)
– Composed of a lipid
bilayer and proteins
– Helps
communication
among cells
Plasma membrane
Cytosol
Tortora
Pages 39-46
– All cellular contents
between the nucleus
and the plasma
membrane is cytoplasm.
– The thick semifluid of
the cytoplasm is the
cytosol.
– 75-90% water.
Cell organelles & cytosol
Generalized Cell
Tortora
Pages 39-40
• Organelles
– Highly
organized
structures
with specific
functions in
the cell.
Mitochondria
Plasma Membrane
• Separates
cell’s interior
from the
extracellular
materials.
Tortora
Pages 39-40
Lipids Are Usually
Triglycerides
Tortora
Pages 39-40
• Contains
– Glycerol
backbone
– 3 fatty acid
chains.
• Can be Saturated
– No double bonds
– Straight
– Solid at room Temp
• Can be unsaturated
– 1 or more double
bonds
– Has bend
– Less solid
Glycerol “heads” are polar, fatty
acids “tails” are non-polar.
How Do Phospholipids
Differ?
• Contains
– Two layers of
phospholipids
– Phospholipids have;
• 2 fatty acid chains
• 1 glycerol backbone
• 1phosphorylated
alcohol
– Tails are non polar
and so hydrophobic
– Heads are polar and
so hydrophilic
Tortora
Pages 39-40
Plasma Membrane
• Bilayer of
phospholipids
• Fatty acid tails
point inward.
– Away from ICF
– Away from ECF
• Phospholipid heads
orient towards ICF
& ECF
• Fluid-like make up.
Tortora
Pages 39-40
Plasma Membrane
• Contains
– Integral Proteins.
• Through bilayer
– Peripheral
proteins.
• Inside or outside
surface
– Most of the
proteins are
glycoproteins
– Cholesterol
molecules
Tortora
Pages 39-40
What Roles Do
Proteins Play?
• Plays role in
selective
permeability
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Ion channels
Transporters
Receptors
Enzymes
Cell identity markers
Anchors for
cytoskeleton
– Cell to Cell
connection
Tortora
Pages 39-40
How Do Viruses Use
Surface Proteins?
• HIV recognizes
CD4 (part of T
lymphocytes)
protein on cell
surface.
• Gains entry &
creates DNA
molecule.
• DNA becomes part
of cell’s DNA.
• Makes more viruses.
Glycoprotein
Plasma Membrane Function
• Passage of water
• Passage of bulk
material
• Selective transport
of molecules.
• Reception of
information.
• Expression of cell
identity.
• Physical connection
with other cells
Plasma membrane
Movement of Materials
Across Plasma Membrane
• Intracellular fluid
(ICF) is found
inside of the cell.
– Cytosol
• Extracellular fluid
(ECF) is found
outside of the cell.
– Interstital fluid
– Plasma
– Lymph fluid
Plasma membrane
Tortora
Pages 41-44
Passive Movement Across
Plasma Membrane
• Passive processes.
– No use of cells
energy.
– Kinetic energy
causes movement of
substances across
membrane.
– Moves down the
concentration
gradient.
– Eventually reaches
dynamic equilibrium.
Plasma membrane
Tortora
Pages 41-44
Passive Movement cont’d
• Simple diffusion.
• Net movement of
molecules or ions
from high
concentration area
to low concentration
area.
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–
–
O2
CO2
ions
small molecules
Polar molecules
Plasma membrane
Tortora
Pages 41-44
Movement of Materials:
Facilitated Diffusion
– Diffusion occurs
with a “helper”
molecule.
– Helper molecule is
a transmembrane
protein.
– Large molecules
such as glucose.
– Lipid soluble
molecules.
Tortora
Pages 41-44
Tortora
Facilitated diffusion: glucose
• Example:
– Glucose attaches
to transporter
protein on outside
of cell.
– Transporter
changes shape.
– Glucose passes
through the
membrane and is
released inside of
cell.
Pages 41-44
Tortora
Osmosis
Pages 41-44
• Osmosis
– Net movement of water
from area of high
concentration to area of
low concentration through
a selectively permeable
membrane.
– Water wanting to move
down the concentration
gradient causes osmotic
pressure.
– Osmotic pressure is the
force required to stop
the movement of water.
Plasma membrane
Active Processes: use ATP
• Cells use ATP (Cellular
energy) to transport
materials.
• Materials move from low
to high concentration
areas. (Up the conc.
gradient)
• Integral proteins are
needed to transport the
material.
• Ex. Sodium/potassium
pump.
Tortora
Pages 45-46
Endocytosis Vs
Exocytosis
Tortora
Pages 45-46
• Cells moving large
objects or molecules
through the plasma
membrane.
– Endocytosis - move
materials into cell.
– Exocytosis - move
materials out of cells.
– Plasma membrane forms a
pseudopod.
– Results in a phagocytic
vesicle.
Endocytosis
Phagocytosis Vs
Pinocytosis
Pinocytosis
Phagocytosis
“Cell drinking”
‘Cell eating”
Exibit 3.2 Quiz
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Contains the genes of the cell.
Involved in the synthesis of lipids, proteins, and
detoxifies some compounds.
3) Acts as a digestive structure.
4) Provides shape and support for the cell.
5) Moves materials across the surface of cells.
6) Provides movement of the whole cell.
7) Packages and delivers proteins for the cell.
8) Provides a location for ribosomes.
9) Builds proteins.
10) Regulates entrance of molecules into the cell and the exit
of molecules from the cell.
Exibit 3.2 Quiz
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Nucleus
Endoplasmic reticulum
Lysosome
Cytoskeleton
Cilia
Flagella
Golgi Apparatus
Rough ER
Ribosomes
Plasma membrane