biol& 160 ch 5

describe the makeup of the cell membrane

a phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward. Contains proteins, cholesterol, and carbohydrates

what molecules are permeable to the cell membrane? why?

small, nonpolar molecules (O₂, CO₂) because they can pass through the hydrophobic membrane

how do impermeable molecules cross the membrane?

through transport proteins (channels/carriers) or vesicles (endocytosis/exocytosis)

simple diffusion vs. facilitated diffusion

simple: no protein, high → low concentration

facilitated: uses a transport protein, high → low concentration

carrier proteins vs. channel proteins

carrier: changes shape to move molecules

channel: forms a tunnel for molecules or ions

diffusion vs. osmosis

diffusion: Movement of solutes from high → low concentration

osmosis: Movement of water across a membrane from low solute → high solute concentration

plant vs. animal cells in different solutions

Hypotonic: animal cells swell/burst; plant cells become turgid

Hypertonic: animal cells shrink; plant cells plasmolyze

Isotonic: animal cells stay normal; plant cells become flaccid

active vs. passive transport

active: requires ATP, moves low → high concentration

passive: no ATP, moves high → low concentration

primary vs. secondary active transport

primary: uses ATP directly

secondary: uses energy from another molecule's gradient

exocytosis vs. endocytosis

exocytosis: moves materials out of the cell

endocytosis: moves materials into the cell

What is ATP and how is it used for energy?

ATP stores energy. Hydrolysis breaks ATP into ADP + Pi and releases energy. Dehydration joins ADP + Pi to make ATP

Exergonic vs. endergonic reactions

Exergonic: Releases energy

Endergonic: Requires energy

Why doesn't glucose break down without enzymes?

The reaction has a high activation energy. Enzymes lower the activation energy

What are enzymes?

Proteins that speed up chemical reactions by lowering activation energy without being used up

Cofactors vs. coenzymes

Cofactor: Inorganic helper (example: Zn²⁺ or Mg²⁺).

Coenzyme: Organic helper (example: NAD⁺ or vitamin B-derived molecules)

Feedback inhibition

The final product stops an earlier enzyme to prevent making too much product

Competitive vs. noncompetitive inhibition

Competitive: Inhibitor blocks the active site

Noncompetitive: Inhibitor binds elsewhere and changes the enzyme's shape

Why is noncompetitive inhibition called allosteric inhibition?

Because the inhibitor binds to the allosteric site, not the active site

What is enzyme denaturation? What causes it?

Denaturation changes an enzyme's shape so it no longer works. Causes include high temperature, extreme pH, and some chemicals

solvent

the substance that dissolves the solute (usually water)

solution

a homogeneous mixture of a solvent and one or more solutes

describe tonicity

a measure of the osmotic gradient of two solutions separated by a semipermeable membrane. it’s the tendency of a cell to lose or gain water in solution

explain the types of osmotic concentrations

isotonic: when 2 solutions have the same osmotic concentrations

hypertonic: the solution with the higher solute concentration (shriveled cell, no water)

hypotonic: the solution with the lower solute concentration (bursting cell/lyse, too much water)

law of thermodynamics

energy can be changed from one form to another but cannot be created or destroyed. some energy lost as heat

why do reactions need activation energy?

all chemical reactions cannot occur without overcoming their activation energy. energy input is required to initiate the reaction

label this cell membrane

1. glycoprotein

2. glycolipid

3. peripheral membrane protein

4. integral membrane protein

5. cytoskeleton

6. cholesterol

7. protein channel

8. phospholipid bilayer

The cell membrane is considered a fluid because

The molecules are separate but loosely attached and can therefore float or move somewhat with respect to one another

What factors need to be in place for osmosis to occur? 

a semipermeable membrane, different concentrations of water and solute on both sides of the membrane

match the state of a plant cell with this extracellular solution:

hypotonic

hypertonic

isotonic

turgid

plasmolyzed

flaccid

match the state of a animal cell with this extracellular solution:

hypotonic

hypertonic

isotonic

lyse

shrink/shrivel

normal

Why do plant and animal cells behave differently in hypotonic solutions?

 

Plants have a cell wall, and animal cells don't

Bulk transport mechanisms involve the movement of vesicles in the transport of materials across the cell membrane. This includes which of the following transport mechanisms?

exocytosis + endocytosis

Where is energy stored in an ATP molecule that is released during hydrolysis?

In the bonds formed between phosphates