Test 3: Cells and Membranes

Receptor mediated endocytosis

cells engulf target substances (ligands) from external environment; these substances bind to receptors on the cell membrane which cause a coated pit/ vesicle to form

• highly selective

most signal receptors are…

plasma membrane proteins

most abundant organic compound on Earth

cellulose (plant cell walls)

Purines (structure and N bases)

AG, 5 membered ring + 6 membered ring

function of protein kinases

transfer phosphates from ATP to protein (aka “phosphorylation”)

function of protein phosphatases

remove phosphates from proteins (aka “dephosphorylation”)

• turn off signal transduction pathway → making protein kinases available for reuse (cell can respond to signal again)

who discovered how epinephrine (hormone) acts on cells (cell signaling)

Earl W. Sutherland

Adding phosphate groups often changes the form of a protein from ____ to ____

inactive to active

Cell Signaling: reception

• binding of signaling mQ to receptor protein in membrane (ligand)

  • ^^highly specific based on shape

  • can happen inside the cell too though

• ligand binding makes receptor protein change shape (most receptors directly activated by this shape change)

What kinds of molecules pass through a cell membrane most easily

small hydrophobic (nonpolar)

is CO2 polar or nonpolar

nonpolar

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.  

true!

nonpolar covalent bonds present between….

all mQs that are dimers

cotransport (secondary transport)

mechanism where a transport protein couples the movement of one solute down its concentration gradient with the movement of another solute against its gradient. This process is akin to using the energy from water flowing downhill to pump another substance uphill

• In plant cells, cotransport often involves hydrogen ions (H+) and nutrients like sucrose.

conditions required for simple diffusion across the cell membrane

small & nonpolar (hydrophobic) mQs

what is a transmembrane protein

A protein that spans the phospholipid bilayer one or more times (perpendicular)

Which molecules are localized on the exterior of a phospholipid bilayer?

phosphate groups (heads of phospholipids)

how do the phospholipids in a plasma membrane stay together

hydrophobic effect / amphipathic nature

what component in cell membrane plays roll in cell-cell recognition

carb chain (attached to glycoprotein)

• Ex: A and B antigens on RBCs to tell blood type

Pyramidines (structure and N bases)

CUT; 6 membered ring

Nitrogenous base pairs are joined by _____

hydrogen bonds

What functional feature(s) does the phosphate group contribute to the structure of a phospholipid?

hydrophilic head, negative charge (phosphate group), diversity (phosphate group can be linked to various small, charged, or polar molecules, creating different types of phospholipids → allows for specialized functions in cell membranes)

most abundant organic compound in living things

proteins

glucose + glucose = ____ by ____

maltose; dehydration synthesis

enantiomers

mQs that are mirror images of one another (isomers)

Turgor pressure

force exerted by water inside the cell against the cell wall; crucial for maintaining structure and firmness of plant cells

• hypotonic solution → more turgid

• hypertonic solution → less turgid

plasmolysis (verb)

plant cells lose water and shrink when placed in a hypertonic solution (plasma membrane retracts from cell wall)

osmoregulation

cells maintain the balance of water and solutes within their environment (crucial for function and survival)

• tonicity plays a role

isotonic

solute concentrations inside = outside; no net water movement

Animal cells thrive in isotonic environments unless they have adaptations for osmoregulation

Eukaryotic vs prokaryotic cells

Eukaryotic: have organelles, nucleus, bigger

Prokaryotic: no organelles, nucleoid, smaller

pinocytosis

(type of endocytosis AT): cell “drinking” by engulfing lique environment from extracellular environment; allows cell to get nutrients form the liquid environment

• nonselective in the molecules it brings into the cell

phagocytosis

(type of endocytosis AT): cell “eating” by engulfing large solid contents from extracellular environment

primary active transport

protein pump

secondary active transport (cotransport)

uses E stored in an electrochemical gradient created by primary active transport (divided into symporters which move two or more substances in the same direction and antiporters which more two or more substances in opp directions

flaccid (adj)

low turgid pressure

Lyse

cell membrane ruptures

• more common in animal cells than plant cells (strong cell walls)

what types of bonds are in fats

ester bonds

makeup of a phospholipid

2 fatty acids (tails) [ester bond] phosphate group attached to glycerol

steroid makeup

lipid with carbon skeleton of 4 fused rings

ex: cholesterol

hydrolytic enzymes

specialized proteins that facilitate the breakdown of macromolecules through hydrolysis (found in lysosomes)

Plasmodesmata

Channels connecting adjacent plant cells for sharing materials (water, nutrients, chemical messages)

Peroxisome

Metabolic compartment (enzymes break down fatty acids for cellular energy)

• form H2O2 which then turns to water (helps with detoxification)

Centrosome

Aids in cell division using microtubules to attach to and pull apart chromatids (in animal cells)

spectrin

peripheral protein that forms a lattice around the inner cell membrane for structural support

thylakoids

flat sacs in chloroplasts responsible for photosynthesis

stroma

fluid filled space inside chloroplasts

what mQs can dissolve in the membrane and cross it with ease

Hydrophobic molecules, such as hydrocarbons, carbon dioxide, and oxygen

Submerging a plant cell in distilled water will result in

cell becoming turgid (distilled water has very few solutes)

how is glucose transported into animal cells

facilitated diffusion using protein carriers (passive, doesn’t require E)