Download Cell Boundaries

Cell Membrane
•Double layer of phosholipids
•Controls movement of
materials in
and out of cells
• Selectively permeable
because it only allows certain
materials into and out of the
cell.
• This membrane is composed of two main groups
of organic molecules:
lipids and proteins.
Lipids:
• The lipid bilayer
-the phosphate “head”; is
polar is attracted to water (hydrophilic)
- the two “tails”; the hydrocarbon
chains are nonpolar and repelled by
water (hydrophobic)
Proteins:
• Embedded in the plasma membrane are cell
surface proteins that allow larger materials to
pass into and out of the cell.
• These proteins are called channels.
Cells
All cells can be
divided into two groups
• Prokaryotes
• Cells that DO NOT
contain a nucleus
• Eukaryotes
• Cell that DO contain a
nucleus and many
specialized “organelles”
Size of a bacterium
Compared to a eukaryotic cell
ALL cells have these 3 things:
1 - Cell Membrane
2 – Cytoplasm
3 – DNA
Organelles -Specialized structures inside a
eukaryotic cell that perform important cell functions
http://www.studiodaily.c
om/2006/07/cellularvisions-the-inner-life-of-acell/
Nucleus
• Membrane enclosed
structure
• Contains the cells
genetic material
(DNA)
• The nucleus directs
the cells activities
• Nuclear envelope: membrane composed of
thousands of pores that surrounds the nucleus
•
•
•
•
Nucleolus – dense region
within the nucleus
where ribosomes are
produced.
Cytoplasm
• Cytoplasm is everything INSIDE of the cell
membrane but OUTSIDE of the nucleus.
• It is the area inside the cell where all the
organelles lie
 Cytoskeleton
– Network of protein
filaments that help a cell maintain shape
• Mitochondrion
converts chemical energy stored in food into the
energy molecule Adeosine Triphosphate (ATP).
Endoplasmic
Reticulum (smooth) membrane where lipid
components of the cell
membrane are assembled
Ribosome – Protein
factories of the cell.
Found free-floating or
attached to the ER
◊ Rough Endoplasmic Reticulum
– Membrane with ribosomes
for making proteins.
• Golgi Apparatus –
Modifies/packages molecule
for export out of cell
• Note- It is near the cell
membrane
Organelles only found in
Animal Cells
Lysosome – contains enzymes
for digesting or recycling
molecules
Centrioles – two tiny
structures in cytoplasm
near nuclear envelope used in cell division.
Organelles only
found in Plant Cells
• Central VacuolesStorage units of cells.
Very large in plants
for holding water.
• Chloroplast – uses
energy from the sun to
convert CO2 molecules
into carbohydrates ub
the process called
photosynthesis.
• Cell walls
• Are stiff fibers of
cellulose (a carbohydrate)
OUTSIDE the cell membrane
• Cell walls support and protect the plant
• Keeps cell from rupturing when osmotic
pressure is too great
VIRUSES
Chapter 19-2
19-2 What is a Virus?
• Core of DNA or RNA; genetic
material surrounded by a
protein coat (Capsid).
• Can reproduce only by infecting
living cells – once inside the
cell, they use the machinery of
the cell to produce more
viruses
• Very small – need an electron
microscope to see
• Capsid – virus’s
protein coat
• Unique shape of
capsid proteins and
spikes enable virus
to attach to a cell
• DNA rests inside
capsid until injected
into host cell
• Cell transcribes and translates the viral genetic
information into viral capsid proteins;
• host cell often destroyed
• Viruses are very and highly specific to the cells
they infect
http://www.npr.org/blogs/
krulwich/2011/06/01/11407
5029/flu-attack-how-avirus-invades-your-body
Cell vs Virus
• Viruses are not enclosed by a cell
membrane.
• Viruses do not have any organelles.
• Viruses do have either DNA or RNA (either
can be single or double stranded) as their
genetic information.
• Viruses cannot metabolize.
• Viruses cannot replicate themselves.
Are Viruses Alive?
• They are on the borderline between living and
nonliving
• Like living things – they reproduce, regulate
gene expression, and evolve.
• But they are not made of cells and cannot live
independently. There is no metabolism, no
homeostasis, etc.
• No. Viruses are not considered living.
Types of Transport
B. Passive Transport
•
•
•
•
•
– DIFFUSION (simple)
The movement of materials into and out of cells
depends on the process of diffusion.
Occurs when there is a difference in concentration
within the solution.
This difference in concentration is called a
concentration gradient.
Particles of a solute and solvent are constantly moving
from areas of high concentration to areas of low
concentration.
These particles continue to move until the
concentrations are equal or reach… equilibrium.
http://highered.mcgrawhill.com/sites/0072495855/student_view
0/chapter2/animation__how_diffusion_w
orks.html
-OSMOSIS (simple)
•Diffusion of water molecules from an area of high
concentration to an area of low concentration.
•This process is called osmosis.
•The increased pressure that
results from an increase of
water is called
osmotic pressure.
C. The Effects of Osmosis
on Cells
The mixture of solutes and solvents are called
solutions.
NOTE: The following terms are based on the concentration
of solute which will then determine the movement of
water.
Hypertonic- “high” levels of solute/Low H20
Hypotonic-”low” levels of solute/high H2O
Isotonic-“equal” levels on both sides of membrane –”tonic”
This is the shrinking of the cell due to water leaving
the cell…
plasmolysis.
93% water
7% solute
95% water
5% solute
This is the bursting of the cell due to water entering
the cell…
cytolysis.
93% water
7% solute
95% water
5% solute
1. This cell solution is _______________
Hypotonic . There is a higher
concentration of solute in the environment than that in the cell.
Thus, the environment solution is said to be
Hypertonic
_________________.
Water will move _______
out of the cell.
This is the shrinking of the cell due to
water leaving the cell…
plasmolysis.
2. This cell solution is _______________
Hypertonic . There is a lower
concentration of solute in the environment than that in the cell.
Hypotonic
Thus, the environment solution is said to be _________________.
Water will move _______
into the cell.
This is the bursting of the cell due to
water entering the cell…
cytolysis.
isotonic
3. A cell is _______________
when the concentration of
solutes in the environment and in the cell are the same.
into and
Equal amounts of water will move _________
out of the cell.
___________
• Facilitated diffusion is diffusion through the
channel proteins in the membrane.
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffu
sion_works.html
Diffusion
Osmosis
Facilitated Diffusion
These are all forms of passive transport
because no energy is required by the cell.
D. Active Transport
• Cells must have a way to maintain
concentrations of important food molecules at
a level different from the concentration level
outside the cell.
• Active transport uses energy to transport
particles through membrane against the
concentration gradient. An example of an
active transport channel is the sodiumpotassium pump.
http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_the_sodi
um_potassium_pump_works.html
D. Active Transport
Bulk Transport
• Energy is required.
• Two kinds:
1. Endocytosis
is the taking in
(engulfing) of
particles
into a cell.
– Two types:
• Pinocytosis is the taking in of liquid or dissolved
materials.
• Phagocytosis is the taking in of large solid
materials.
2. Exocytosis is the removal of wastes out of
a cell.