Cell Membrane, Transport, Enzymes, & Energy Unit 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 MEMBRANE The 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 Phospholipids make up the majority of both layers of the cell membrane. Carbohydrate chains (glycolipids & glycoproteins) are always on the OUTSIDE of the membrane. Cholesterol adds structure and stability to the cell membrane. It makes up about 20% of the cell membrane.

Phospholipids Hydrophilic phosphate heads = love water Hydrophobic fatty acid tails = repel water

Phospholipid Bilayer

This process is called Diffusion.  Solute The sugar molecules are spreading out.  Solvent

Molecules always move from HIGH concentration to LOW concentration 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).

This is called moving WITH the concentration gradient (HIGH to LOW). Does the cell have to use energy for this? NO This is called PASSIVE Transport.

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 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 HIGH Concentration Large or polar molecules MUST diffuse through a Channel Protein LOW Concentration

Concentration Gradient

Does the cell have to use energy for this? NO This is called PASSIVE Transport.

HIGH Concentration LOW Concentration

Active Transport to LOW Concentration MUST USE ENERGY HIGH Concentration

ACTIVE TRANSPORT This 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

This is called the SODIUM (Na+)/POTASSIUM (K+) Pump Active Transport! 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.

Other Transport Mechanisms Into the cell   Out of the cell   Import Export

Types of Endocytosis Phagocytosis = takes in food/large particles Pinocytosis = takes in fluid Receptor Mediated = will only take in specific molecules

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

so they are very specific ENZYMES ENZYMES 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.

Higher Cost (more energy required) LOWER Cost (less energy required) Activation energy is like the COST of the reaction & the enzyme is like a COUPON because it lowers the cost.

Enzyme-Substrate Complex Reactants = SUBSTRATES Substrates bind to the enzyme at the ACTIVE SITE to provide a place for the reaction. The Enzyme is NOT permanently CHANGED in the reaction = Reusable

The Cell’s Energy Molecule = ATP ATP = Adenosine Triphosphate 2 Phosphate groups 3rd Phosphate group Adenine Ribose triphosphate Chemical bonds store ENERGY Adenosine

ATP - P = ADP RELEASES energy   This is called HYDROlysis

ADP  ATP This is called PHOSPHOrylation ADP + P = ATP STORES energy   Glucose gets broken down during Cellular Respiration so that energy can be stored in ATP.

The products go through the occurs in the occurs in the occurs in the The products go through the Is broken down during produces produces TOTAL 36 produces Cellular Respiration Equation C6H12O6 + 6O2  6CO2 + 6H2O + 36ATP 32

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