Quiz 3 Chap 5/6 Flashcards
how is NADH significant in the electron transport chain?
- NAD+ coenzyme is previously transferred electrons from organic compounds
- each NADH represents stored energy to make ATP, NADH electron carriers pass/donate electrons to compounds in the ETC
- carriers alternate reduced and oxidized states as they accept and donate electrons
how does the ETC work
- O2 pulls electrons down the chain, yielding energy for ATP in a series of redox reactions
- electrons are passed through many proteins (including cytochromes containing Fe) and drop in free energy as they go down the chain
- this causes proteins in the cristae to pump H+ (protons) from the matrix to the intermembrane space
significance of ETC being a series of small steps
ETC functions to break the large free-energy drop from food into smaller steps, releasing energy in manageable amounts
ETC structure
multi-protein complex in the cristae (inner membrane)
chemiosmosis
use of energy in a H+ (proton) gradient to drive cellular work
how is ATP made via chemiosmosis, and what is a proton-motive force?
- H+ moves back across the membrane via ATP synthase (turbine-like)
- energy from this H+ gradient causes phosphorylation of ADP to ATP
proton motive force – H+ gradent
significance of oxygen during ETC stage
electrons are passed to oxygen at the end of the chain to form H2O, chain can’t function without oxygen to accept them
flow of energy during cellular respiration
glucose - NADH - ETC - proton-motive force - ATP
how many ATP are produced during each stage of respiration (per glucose)
glycolysis - 2
citric acid cycle - 2 (1 per turn, 2 turns per glucose)
oxidative phosphorylation - 26-28
evolutionary significance of glycolysis
- occurs in nearly all organisms
- evolved in ancient prokaryotes before there was atmospheric oxygen
- glycolysis and citric acid cycle lead to many different catabolic/anabolic pathways
***fats and proteins can also be used for glycolysis, with additional steps before
structure of the plasma membrane
- selective permeability, some substances pass through more easily
- fluid mosaic model: fluid structure with a “mosaic” of various proteins embedded in it
- like jello, phospholipids and proteins can move within the bilayer
how does the plasma membrane change in response to temperature?
- at cool temps, membranes switch from fluid to solid (specific temp depends on type of lipids)
- membranes rich in unsat. fats more fluid
importance of membrane fluidity, how they maintain it
membranes must be a specific fluidity in order to function properly
- steroid-cholesterol restrains movement of phospholipids in warm temps and maintains fluidity by preventing tight packing in cool temps
peripheral vs intergral proteins
peripheral: bound to surface of membrane
integral: penetrate hydrophobic core
6 functions for membrane proteins
transport enzymatic activity signal transduction cell-cell recognition intercellular joining attachment to cytoskeleton and extracellular matrix
how do cells recognize each other?
specific molecules on the plasma membrane (glycolipids and glycoproteins)
- these are unique among species, individuals, and even cell types within individuals
which molecules pass/do not pass through plasma membrane?
- hydrophobic (nonpolar) molecules dissolve in lipid bilayer and pass through membrane
- hydrophilic and polar molecules (sugars) must be transported by proteins
mechanisms and benefits of facilitated diffusion
*speeds up passive movement of molecules and allows for the transport of polar molecules!
- channel proteins: hydrophilic channels that allow specific molecules to cross (i.e. ion channels)
- aquaporins: facilitate the passage of water
- carrier proteins: bind to molecules, change the molecule’s shape to shuttle them across the membrane
diffusion
tendency for molecules to spread evenly in space without energy investment
dynamic equilibrium
molecules cross both ways across a selectively permeable membrane, diffusing down their conc. gradient
osmosis
diffusion of water across a selectively permeable membrane from a less concentrated (hypotonic) to a more concentrated (hypertonic) solution
tonicity
ability of a solution to cause cell to lose/gain water
types of tonicity in solutions
isotonic: solute same conc. as cell, no net movement
hypertonic: solute conc. greater than cell, cell loses water
hypotonic: solute conc. less than cell, cell gains water
what tonicity environment do plant and animal cells prefer?
animals - isotonic (hypotonic solution can cause plasmolysis)
plants - hypotonic (prefer to be turgid, not flaccid)
active transport and its importance
proteins move substances against conc. gradient, requiring ATP
- allows cell to maintain conc. gradient different from surroundings (homeostasis)
- sodium-potassium pump is one type
signal transduction pathway
series of steps by which a signal that reaches a cell’s surface is converted into a specific cellular response
(2nd step of cell signaling)
types of short-distance communication in animals
cells communicate using messenger molecules called local regulators
- paracrine signaling: secreting cell releases local regulator molecules to many nearby target cells
- synaptic signaling: one neuron sends neurotransmitters to a target cell
how are hormones used in organisms?
*used for long-distance signaling, released by endocrine cells
animals - travel through blood
plants - often on exterior waxy coating
what are the names of junctions between plant and animal cells?
plants - plasmodesmata
animals - gap junctions
how do slime molds use short-distance signaling?
slime mold cells signal each other locally when using cAMP when food is scarce, causing them to come together and form a fruiting body
how is endocrine (hormonal) signaling used to regulate blood glucose?
- endocrine signaling is used when glucose falls out of 70-110 mg/mL range
- 2 pancreatic hormones are used: insulin and glucagon
- glucagon is used when glucose is too low; converts glycogen to glucose in the liver
- insulin is used when glucose is too high; converts glucose back to glycogen storage in liver
what is vasopressin and how is it used in long-distance signaling?
- vasopressin is an anti-diuretic hormone made and secreted by the hypothalamus and stored by the pituitary gland
- it travels to the kidney through blood and signals the kidney to reabsorb water, concentrating urine
what was Earl Sutherland’s discovery about epinepherine?
- epinephrine only caused the breakdown of glycogen in the presence of an enzyme when living cells were a part of the mixture
- epinephrine needed a receptor on the cells’ plasma membrane to transmit the signal
- cells receiving signals have 3 processes: reception, transduction, and response/regulation
what are the 3 stages of cell signaling?
- reception
- signal transduction
- regulation
reception
- water-soluble signal molecule (ligand) binds to a highly specific receptor protein in plasma membrane, causing the protein to change shape
- shape change is initial transduction of signal
signal transduction
multi-step pathway that amplifies signals, relaying them from receptors to target molecules (proteins)
- a few molecules produce a large cellular response
- receptor activates a protein, which activates another…until response activated
- with each step, the signal is transduced into a different form, with shape change from a protein
what are intracellular receptors, and which hormones typically use them?
- found in cytosol or nucleus of target cells
- activated by small, hydrophobic molecules like steroid and thyroid hormones
- forms a hormone-receptor complex that can act as a transcription factor (turn genes on/off)
- receptors revert back to inactive state when signal molecules leave
regulation
one or more cell activities impacted
- usually regulates synthesis of enzymes or other proteins by turning genes on/off (final activated molecule may be a transcription factor)
- other pathways regulate the activity of enzymes (i.e. epinephrine turns on a protein that converts glycogen into glucose for quick energy)
phosphorylation cascade
phosphate transferred between proteins, catalyzed by a kinase enzyme
output response
cell’s response to an extracellular signal
how does yeast use signal transduction pathways?
- sometimes divides mitotically, producing differnet cell types
- different cells recognize each other by lignins on membrane
- binding of signal molecule to receptor causes schmoo (bud) formation
what is apoptosis?
programmed/controlled cell suicide
- requires both a “death signal” from an outside cell and a “death receptor”
- happens when proteins that accelerate apoptosis override those that “put on the brakes”
- cell is chopped and packaged into vesicles to be digested by a scavenger cell (so no death enzymes leak and damage neighboring cells)
evolutionary significance of apoptosis
- evolved early in animal evolution, important in shaping organisms in embryogeneis
what can trigger apoptosis?
- death-signaling ligand
- DNA damage
- protein misfolding in ER
what diseases involve apoptosis?
Parkinson’s, Alzheimer’s, certain cancers
