Cell Membrane, Transport, Enzymes,
& EnergyUnit 4 Review
The Cell Membrane
helps maintain Homeostasis by regulating transport of
materials in/out of the cell.
Function of the Cell Membrane
The Cell Membrane is like the
of the cell because it controls what can come in and out of
the cell.
Security Guard
PLASMA/CELL MEMBRANEThe Cell Membrane is
the barrier between the cytoplasm and the ExtraCellular
Fluid (outside) of the Animal
Cell.
In Plant Cells (and other types), it separates the
cytoplasm from the Cell Wall.
Cell Membrane Structure
Cholesterol adds structure and stability to the cell membrane. It makes up about 20% of the cell membrane.
Carbohydrate chains (glycolipids & glycoproteins) are always on the OUTSIDE of the membrane.
Phospholipids make up the majority of both layers of the cell membrane.
Phospholipids
Hydrophobic fatty acid tails = repel water
Hydrophilic phosphate heads = love water
Phospholipid Bilayer
This process is called Diffusion.
Solute
Solvent
The sugar molecules are spreading out.
Molecules always move from HIGH concentration to LOW concentration. It takes added ENERGY to move
from low concentration to high concentration.
Semipermeable means that it is selective about what can enter or leave, kind of like a picky eater.
Molecules that easily diffuse across the membrane are Hydrophobic (O2/CO2) or SMALL & Uncharged/Polar (H2O).
Sugars can NOT diffuse because of SIZE (too big). Ions can NOT diffuse because of CHARGE (charged & large molecules can not get across).
Does the cell have to use energy for this? NO
This is called PASSIVE Transport.
This is called moving WITH the
concentration gradient (HIGH
to LOW).
The diffusion of WATER is called OSMOSIS.
This means that H2O is moving from
where there is MORE H2O & LESS
solutes TO where there is LESS H2O &
MORE solutes.
Does the cell have to use energy for this? NO
This is called PASSIVE Transport.
Hypotonic Solution = Cell swells because H2O diffuses (osmosis) INTO the cell.
Animal cells may burst. Plant cells have increased turgor pressure but are protected by
their cell walls.
Isotonic solution = SAME concentration as the cytoplasm of the cell. H2O diffuses (osmosis) IN & OUT
of the cell at the same rate. The cell stays the same size.
Hypertonic Solution = Cell shrinks because H2O diffuses (osmosis) OUT of the cell.
Facilitated Diffusion
Large or polar molecules MUST diffuse through a Channel Protein
LOW Concentration
HIGH Concentration
Concentration Gradient
Does the cell have to use energy for this? NO
This is called PASSIVE Transport.
HIGH Concentration
LOW Concentration
Active Transport
LOW Concentration
HIGH Concentration
MUST USE ENERGY
to
ACTIVE TRANSPORTThis is moving AGAINST the
concentration gradient
(LOW to HIGH)
Does the cell have to use energy for this? NO
That is why it is called ACTIVE Transport!
(ATP is the energy molecule)
ENERGY
The Na+/K+ Pump moves 3 Na+ ions out of the cell & 2 K+ ions into the cell for every molecule of ATP. This ION PUMP controls Neuron function.
This is called the SODIUM (Na+)/POTASSIUM (K+) Pump
Active Transport!
Other Transport Mechanisms
Into the cell
Out of the cell
Import Export
Pinocytosis = takes in fluid
Phagocytosis = takes in food/large particles Receptor Mediated = will only
take in specific molecules
Types of Endocytosis
Vesicle from Golgi Apparatus
Paramecia have a Contractile Vacuole that
allows water to be pumped OUT of the cell because
they live in a HYPOTONIC environment. This takes
ENERGY but it allows them to maintain
HOMEOSTASIS.
Contractile Vacuoles
ENZYMESENZYMES are
PROTEINS that are used in many chemicals
reactions.
They are necessary for living things because they SPEED UP (accelerate)
important chemical reactions by lowering the amount of ACTIVATION ENERGY needed to start
the reaction.
Enzymes & Substrates have to fit together
(complementary shapes) at the ACTIVE SITE
so they are very specific
Enzymes are reusable because they are not
permanently changed in the reaction.
Enzymes help weaken or form chemical bonds so that the reaction takes
less energy to occur.
Activation energy is like the COST of the reaction
& the enzyme is like a COUPON because it
lowers the cost.
Higher Cost (more energy required)
LOWER Cost (less energy required)
Reactants = SUBSTRATES
Substrates bind to the enzyme at the ACTIVE SITE to
provide a place for the reaction.
Enzyme-Substrate Complex
The Enzyme is NOT permanently CHANGED in the reaction = Reusable
The Cell’s Energy Molecule = ATP
Adenine Ribose2 Phosphate
groups3rd Phosphate
group
Adenosine
triphosphate
ATP = Adenosine Triphosphate
Chemical bonds store ENERGY
ATP - P = ADP RELEASES energy
This is called HYDROlysis
ADP ATPADP + P = ATP STORES energy
Glucose gets broken down during Cellular Respiration so that energy can be stored in ATP.
This is called PHOSPHOrylation
occurs in the
produces
Is broken down duringThe products go through the
occurs in theoccurs in the
produces
produces
32
TOTAL36
Cellular Respiration Equation
C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP
Take the Multiple Choice Quiz
& Check Your Answers!