Honors Biology - The Working Cell Test

Severn School Honors Bio

fluid mosaic model

• used to describe structure of plasma membrane (phospholipid bilayer) as fluid + mosaic

1. fluid

   1. fatty acid chains → plasma membrane contains a mix of both saturated and unsaturated fa. chains → allows for permiability (not too close to be solid; not too far for LDFs)

   2. cholesterol → is a lipid = hydrophobic molecule → function is to stabilize the molecule (in cold, risk of getting solid so cholesterol physicallly blocks from getting too close) (in warm, risk of moving away→ no LDFs, so cholesterol holds together

2. mosaic → made up of many small parts like phospholipids, cholesterol, and proteins

plasma membrane is _____

selectively permeable, meaning that only certain substances can cross: small nonpolar molecules

energy barrier

transport proteins

• allow specific ions or molecules to enter/exit the cell

• uncharged solutes can easily pass w/ out help of a protein important (ex. O₂→ required in cell respiration)

• charged solutes require help from transport proteins (specific to each ion/molecule)

enzymes

• function: to speed up/catalyze chemical RXNS

• some membrane proteins are enzymes

• ex. mitochondria had enzymes on interior membrane (cristae); more membrane → more enz. → more ATP

attachment proteins

• attach to ECM and cytoskeleton

• help to support the membrane

• can coordinate external + internal changes

• ex. intergin protein

receptor proteins

• receptors that allow a cell to receive a signal

• used to detect glycoproteins on other cells

junction proteins

• form intercellular juntions that attach adjacent cells

• ex. tight, anchoring, and gap

glycoproteins

• polypeptide modified in RER w/ sugar molecs

• serves as ID tags, can be recognized by receptor proteins of other cells

Passive Transport (diffusion)

• spontaneous movement of a substance from an area with high concentration to one with low concentration (can occur w/out a membrane)

• does not require energy

• down the concentration gradient: [high] to [low]

• simple diffusion → small, nonpolar molecules, channel proteins not used

• facilitated diffusion → use channel proteins; for polar, small substances ex. channel proteins (specific molecules) and aquaporin

Active Transport

• transports small + charged particles

• specific substances

• used energy (ATP) → comes from ATP hydrolysis where energy stored in bonds is released (ATP→ADP+P)

• protein pumps (transport protein)

• against the concentration gradient: [low] → [high]

• like an airlock

osmosis

• diffusion of water from high water concentration to low water concentration across a selectively permeable membrane

• see diagram on notes sheet 2

tonicity (hypotonic, isotonic, and hypertonic)

• the ability of a surronding solution to cause a cell to gain or lose water

• described by terms hypotonic, isotonic, and hypertonic

• hypotonic solution → has a lower solute concetraction compared to that of another solution (water goes into cell); causes cell lysis in animal cells and turgid (normal) in plant cells

• isotonic solution → has the same solute concentration as that of another solution (water goes in and out); normal for animal cells and flaccid for plant cells

• hypertonic solution → has a higher solute concentration compared to that of another solution (water goes out of cell); causes shriveling in animal cells and plasmolysis (shriveled) in plant cells → pulls away from cell wall

osmoregulation

• some cells have mechanisms to survive hypo and hypertonic solutions

• ex. contractile vacuoles → helps to maintain balance

Exocytosis

• function → to remove large/bulky materials (ex. large molecs, liquid, large material) from cell

• transports nonspecifically

• no gradient involved

• Process → vesicles fuse with plasma membrane to release contents

• energy required(to remodel cytoskeleton → NO QUESTIONS ABT)

Endocytosis

• function →the process of taking in large/bulky materials (ex. large molecules, liquids) into the cell

• phagocytosis → general term that means to bring large materials into the cell (energy req***)

  • transports non-specifically

  • no concentration gradient

  • does not use transport proteins → plasma membrane folds in on itself

• receptor mediated endocytosis → brings large materials in attached to receptor proteins (energy req***)

  • transports specific substances (b/c uses receptor proteins)

  • no gradient

  • uses receptor proteins to bing to specific molecule then is engulfed

• pinocytosis → purpose to bring liquids into the cell

  • no gradient

  • transports non-specifically

  • does not use transport proteins → plasma membrane folds in on itself

protein structure diagram types

• ball and stick → shows outside characteristics, feeling for atom amounts and idividual atoms/bonds

• space filling → shows arons and any empty space; area occupied by atoms

• cartoon/ribbbon → show structural details and secondary structure

• molecular surface → shows overall shape/topography and water accesibilty; surface R-groups

Enzyme + Substrate Structure

• fit structurally like a lock and key

• active site → contains substrate binding site and catalytic site (where RXN occurs)

induced fit

• shape of the active site changes upon binding of the substrate

• substrate induces a shape change b/c change in attractive forces (IMFs)

• make it easier for RXNs to occur b/c substrate is more unstable

activation energy

• minimum amt of energy required for reactant molecules before they can undergo a chemical reaction

• enzyme lowers this barrier to increase reaction rates, making processes more efficient.

• see graph on page 3 notes 4

How do enzymes catalyze reactions?

Enzymes catalyze reactions by lowering the activation energy needed for reactants to undergo a chemical reaction, allowing for faster reaction rates and increased efficiency. see page 4 notes 4

Enzyme Inhibition

• chemicals that interfere/inhibit enzyme activity; function reduced or completely gone

• competitive inhibition → inhibitor blocks binding of substrate; substrate competes for active site; can be reversed by having excess substrate → out competes it

• noncompetitive inhibition → inhibitor binds to the enzyme at the allosteric site which causes the active site to change shape, preventing substrate binding

• can be intentional to control cellular metabolism (chem RXNS in cell) → see notes 5 diagram KNOW → negative feedback loop

• can also be accidental ex. cyanide + hemaglobin