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

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