Unit 3 Exam Flashcards
How are membranes held together?
weak hydrophobic interactions
Which type of fat makes it hard for membranes to solidify?
unsaturated because the extra carbon bonds cause kinks in the tails that change the structure
What does cholesterol do in animal cell membranes?
reduces membrane fluidity at moderate temperatures by reducing phospholipid movement and also makes sure membranes do not solidify at low temperatures.
What are peripheral proteins?
proteins bound to the membrane surface
What are integral proteins?
they penetrate hydrophobic core
What are transmembrane proteins?
span the membrane
What does the plasma membrane do?
controls the exchange of materials between the cell and its surroundings
What is the fluid mosaic model?
explains how membranes regulate molecular traffic across the membrane
What do carrier proteins do?
they undergo subtle changes that moves the solute-binding site across the membrane
What is exocytosis?
when transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell (used in a lot of secretory cells)
What is endocytosis?
macromolecules that are taken into the cell in vesicles (phagocytosis and pinocytosis)
What happens in a metabolic pathway?
a molecule is changes in a series of steps to make a product and each step is catalyzed by a specific enzyme
What are catabolic pathways?
release energy by breaking down complex molecules into simpler compounds
What are anabolic pathways?
consume energy to build complex molecules from simpler ones
What is the first law of thermodynamics?
the energy of the universe is constant - energy can be transferred or transformed but cannot be created or destroyed
What is the second law of thermodynamics?
as energy is transferred/transformed, some energy gets lost as heat cannot do work
What do exergonic reactions do?
release energy to surroundings
What do endergonic reactions do?
absorb free energy from surroundings
What are the three main kinds of work that a cell does?
chemical work, transport work, mechanical work
What is energy coupling?
the use of exergonic processes to drive endergonic ones
How do enzymes work?
lowers the activation energy of a reaction so it will happen faster
What is the reactant that an enzyme acts on?
substrate
What influences enzyme activity?
temperature and pH
What are cofactors?
nonprotein helpers
When do enzyme inhibitors become permanent?
when the inhibitor forms covalent bonds
How do competitive inhibitors work?
block the substrate from entering the active site
How do noncompetitive inhibitors work?
bind to a part away from the active site to change the shape of the active site
What is allosteric regulation of enzymes?
occurs when a regulatory molecule binds to a protein at one site and affects the proteins function at another site
What is cooperativity?
happens when a substrate binds to one active site and triggers a shape change in the enzyme that stabilizes the active form for all other sites
What is feedback inhibition?
the end product of a metabolic pathway shuts down the pathway to prevent wasting
Where is cellular respiration performed?
in the mitochondria
What happens in oxidation?
loss of electrons
what happens in reduction?
gain of electrons
Why does cellular respiration happen in a series of steps?
to slow down the conversion of energy and make it manageable and controlled
What do dehydrogenases do?
remove a pair of hydrogen atoms from the substrate
Where does the electron transport chain take place?
the inner membrane of the mitochondria
What does NADH do in the electron transport chain?
passes the electrons to the transport chain where they can be transferred in a series of small and manageable redox reactions
What is the final electron acceptor?
O2
What are the three stages of cellular respiration?
- glycolysis
- pyruvate oxidation and the citric acid cycle
- oxidative phosphorylation, electron transport chain, and chemiosmosis
When does substrate level phosphorylation occur?
in glycolysis and the citric acid cycle
How does substrate level phosphorylation work?
when an enzyme helps make ATP - the substrate has the extra phosphate that is added to ADP to make ATP
Where does glycolysis take place?
the cytoplasm
What is the energy investment phase of glycolysis?
when 2 ATP are used to split glucose into 2 pyruvates
What is the energy payoff phase in glycolysis?
when 4 ATP are made and 2 NAD+ are reduced into NADH, producing oxidized pyruvate and water
What is the preparatory reaction?
when pyruvate is converted to acetyl CoA in the mitochondria before entering the citric acid cycle
What are the three steps in the preparatory reactions?
- the pyruvate releases its first CO2
- NAD+ is reduced to NADH
- coenzyme A is added to make acetyl CoA
What does the citric acid cycle do?
oxidizes pyruvate and produces 1 ATP, 3 NADH and 1 FADH2 PER PYRUVATE MOLECULE (so double number for products from one glucose molecule)
What two molecules hold most of the energy from glucose?
NADH and FADH2
What do NADH and FADH2 do for the electron transport chain?
donates their electrons to power ATP synthesis through oxidative phosphorylation
Does the electron transport chain directly produce ATP?
No, the electrons that are passed down pumps H+ ions from the mitochondrial matrix to the inter membrane space
describe the process of chemiosmosis
H+ moving back and forth across protein complexes until it moves into binding sites on the rotor of ATP synthase, causing it to spin in a way that catalyzes phosphorylation
Is all the energy in a glucose molecule transferred to ATP?
No, only 34% is as the rest is lost as heat
What does a cell do if there is no oxygen for cellular respiration?
uses glycolysis and then anaerobic respiration/fermentation
What are the final electron acceptors of anaerobic respiration?
alcohol, lactic acid, sulfate ion
What are the two steps of alcohol fermentation?
- releases CO2 from pyruvate
- Makes NAD+ and ethanol
What happens in lactic acid fermentation?
pyruvate is reduced directly to form lactate and NAD+ and there is no release of CO2
