Transcript The CELL MEMBRANE

Unit 2A
Cells, Cell Membrane, Cell Transport
Label, cut and glue into notebook
The Cell: smallest basic unit of ALL life
NOT THIS 
Cells vary in SIZE and STRUCTURE (depends on what they do)
Skin cells
Neuron (nerve cells)
Red Blood Cells (RBC)
Prokaryote
Bacteria - simple
No nucleus
No membrane-bound organelles
Unicellular
P B No No
Eukaryote
Ribosomes
Cell membrane
Cytoplasm
Plants, Animals - complex
Has a nucleus
Has membrane-bound organelles
Most are multicellular
Can specialize for certain
functions (absorption,
transmitting nerve responses)
ORGANELLES- "little organs" within the cell
that perform specific functions
Brain
• The nucleus is to the cell what the __________is
to a person.
Skin
• The cell membrane is to a cell what the ________
is to a
person.
ENDOPLASMIC RETICULUM
Canals and channels that connect cell membrane to
nucleus and to organelles within the cell
Function = transport system
Smooth ER (lipid synthesis)
Rough ER (contains ribosomes for protein manufacture)
Golgi Apparatus - Flattened membranes;
Function = package and delivery of proteins produced
by the ribosomes
Proteins are exported in vesicles
Lysosomes - contain digestive enzymes to break down
substances (“suicide sac”)
Enzymes break down
substances in the cell,
such as food or worn out
cell parts, even bacteria.
Mitochondria ( The “powerhouse” of the cell )
Chemical energy from food is converted to a useable form of
energy and stored in ATP -- process is called Cellular
Respiration
CYTOSKELETON - made of microfilaments and
microtubules which maintains shape of cell and
functions in movement
Cilia – hair-like fibers that help to move substances
through the body
Flagella – long whip-like tails also used to move
substances through the body.
Cytology = the study of cells
All Animal Cells have 3 main parts
●Nucleus
●Cytoplasm (cytosol)
●Cell Membrane (selectively permeable)
The Nucleus = control center “brain” to the cell.
contains most of your genetic information (DNA)
“nucleolus” = ribosomes (makes proteins).
The cytoplasm (cytosol) the area between the
nucleus and the membrane. It holds everything in
place.
Many metabolic reactions occur in this area.
Do you remember what
metabolism is?
the chemical processes by which a plant
or an animal uses food, water, etc., to
grow and heal and to make energy
storing molecules called ATP.
The CELL MEMBRANE (referred to as a “fluid mosaic model”)
controls/regulates what comes in and what goes out of the
cell. https://www.youtube.com/watch?v=y31DlJ6uGgE
Lipid bilayer (phospholipids) embedded with various proteins to help
regulate what comes across the membrane and carbohydrates to help
interact with substances in the external environment.
Phospholipids are made up of hydrophilic (“water loving”)
heads (+) and hydrophobic tails (“water fearing”) (non-polar)
Due to these properties, the cell membrane is able to
coexist with water and forms a lipid bilayer around the
cell.
Integral & Peripheral Membrane Proteins - embedded
asymmetrically throughout the lipid bilayer used to
assist larger molecules across the cell membrane.
Many Functions of Membrane Proteins
“Channel”
Outside
Plasma
membrane
Inside
Transporter
Enzyme
activity
Cell surface
receptor
Cell adhesion
Attachment to the
cytoskeleton
“Antigen”
Cell surface
identity marker
Carbohydrates – located on the outside of the cell membrane
and serves as recognition sites for other cells and molecules.
Carbohydrate + Protein = Glycoprotein
Carbohydrate + Lipid = Glycolipid (WBC  cancer cell)
Membrane carbohydrates
• Play a key role in cell-cell recognition
– ability of a cell to distinguish one cell from
another
• antigens
– important in organ &
tissue development
– basis for rejection of
foreign cells by
immune system
Cell Transport : Movement of Substances Across the Membrane
Cells must bring in
materials, like food and
oxygen and remove
wastes.
These processes occur
at the cell membrane.
PHOSPHOLIPID
BILAYER
Which of these would be the most
efficient? (Agar Lab)
Increasing surface area can
increase the cell’s efficiency moving
substances.
Cells of the digestive system have
finger-like projections called villi
that aid in absorbing nutrients.
2 TYPES OF CELL MEMBRANE TRANSPORT:
https://www.youtube.com/watch?v=RPAZvs4hvGA
* PASSIVE
* ACTIVE
3 TYPES OF PASSIVE TRANSPORT
•Diffusion
•Facilitated Diffusion
•Osmosis
1. Diffusion – moving substances from areas of high
concentration to low concentration; molecules tend to
spread out.
This process
requires no energy.
Animation : How Diffusion Works
2. Facilitated Diffusion –
https://www.youtube.com/watch?v=aubZU0iWtgI
Embedded transport proteins used as passageways.
Requires NO ENERGY!
Animation - How Facilitated Diffusion Works
3.OSMOSIS - movement of water molecules and ONLY
WATER from areas of high concentration to low
concentration.
https://www.youtube.com/watch?v=eQsAzXr0UCU
Aquaporins – specialized membrane channels that allow
water to move very rapidly across the cell membrane.
RBC’s
Kidneys
plants
Animation: How Normal Osmosis Works
There are 3 types of solutions that affect Osmosis:
- Hypertonic
SALT
- Hypotonic
- Isotonic
SUCKS
Solution  Solvent (usually water)+ Solute (can be anything else i.e. sugar, salt, etc.)
Affects of Different Solutions during Osmosis:
1) Hypertonic solution
• A solution with a greater solute concentration
compared to another solution.
•3% NaCl
•97% H2O
•Water
•moves
•OUT!
•Red Blood Cell
solution
•5% NaCl
•95% H2O
2) Hypotonic solution
• A solution with a lower solute concentration
compared to another solution.
•Water
•moves
•IN!
•3% Na
•97% H2O
•Red Blood Cell
solution
•1% Na
•99% H2O
3) Isotonic solution
• A solution with an equal solute concentration
compared to another solution.
•3% Na
•97% H2O
•Water
•moves
•IN & OUT
•@ same rate!
•Red Blood Cell
solution
•3% Na
•97% H2O
Active Transport – movement of molecules from
areas of low concentration to high concentration and
requires energy (ATP)
This is easy !!!
This is hard work!!!
Adenosine Triphosphate (ATP)
energy storing compound containing Adenine, Ribose and three
Phosphate groups.
Energy is stored in the
bonds between the
Phosphates.
When a bond is broken
between the
phosphates, energy is
released – usually to
drive endergonic
reactions.
Animation
How the Sodium-Potassium Pump Works
Types of Active Transport
•1. Protein Pumps - require
energy to do work
–Example: Sodium / Potassium Pumps
are important in nerve responses in order
to propagate electrical signals that travel
along the nerves..
•Protein changes shape to
move molecules: this requires
energy!
2. Endocytosis: (phagocytosis & pinocytosis)
• takes bulky material into a cell
• Uses energy (ATP)
• Cell membrane in-folds around food
particle“cell eating” forms food vacuole &
digests food
- Cell membrane in-folds around fluids
“cell drinking”
• This is how white blood cells eat
bacteria!
3. Exocytosis: - (secretion) forces
bulk material out of cell.
* The membrane surrounding the
material fuses with the cell
membrane and the cell changes
shape – requires energy (ATP)
Ex: Hormones or wastes released
from cell
How Organisms Deal with Osmotic Pressure
•
Paramecium
(protist) removing
excess water
video
•Bacteria and plants have cell walls that prevent them from overexpanding. In plants the pressure exerted on the cell wall is called
tugor pressure.
•A protist like paramecium has contractile vacuoles that collect water
flowing in and pump it out to prevent them from over-expanding.
•Salt water fish pump salt out of their specialized gills so they do not
dehydrate.
•Animal cells are bathed in blood. Kidneys keep the blood isotonic by
removal of excess salt and water.