Lecture 11-15 Flashcards
What is the role of electrogenic pumps?
transport protein that generates voltage (charge difference) across a membrane
How does the proton pump function inside the cell?
- pumps protons into the extracellular fluid using ATP
- movement of positive charge (hydrogen) against a gradient
- then create a gradient for H+ back into the cell
What kind of transport is the sucrose-hydrogen pump?
active cotransport
Bulk transport is a form of active transport, what is its function?
- large molecules like polysaccharides and proteins cross the membrane in bulk via vesicles
- requires ATP
Name the types of bulk transport.
1) exocytosis
2) endocytosis
- receptor mediated
- pinocytosis
Compare exocytosis, endocytosis, pinocytosis and receptor mediated endocytosis.
exocytosis: transport vesicles migrate to the membrane, fuse with it, and release their contents
endocytosis: cell brings materials into the cell by outfolding the cell membrane and surrounding it
pinocytosis: creates an infolding of the plasma membrane to bring in the material
receptor mediated endocytosis: ligand binding to receptor triggers endocytosis
What is an enzyme and what is its function?
- protein catalyst
- facilitates chemical reactions
- not consumed by the reaction
- substrates enter the active site of the enzyme, forming an enzyme-substrate complex
- products leave the active site and the enzyme is now ready for another reaction
Where are the sites of enzyme activity in the cell?
- cytosol
- plasma membrane
- endomembrane
- mitochondrial membrane
- thylakoid membrane
Enzymes are inherited from a common ancestor, meaning…?
enzymes are subject to natural selection
How did enzyme structure and function evolve?
DNA to RNA to enzyme
Artificial selection can change enzyme structure and function how?
by causing mutations in DNA and amino acid changes in the enzyme
How can enzyme activity be affected?
- pH
- temperature
- concentrations of substrates and products
- inhibitors
- activators
What happens when the reaction rate increases due to enzymes?
increase in substrate concentrations, then stabilizes due to all the enzymes having a substrate in their active sites
Compare cofactors, activators, allosteric activators, and inhibitors.
-all factors that can affect enzyme activity
cofactors: nonprotein enzyme helpers by increasing enzyme activity
activators: increase enzyme activity by stabilizing it
allosteric activators: binds to allosetric regulatory site
inhibitors: decrease enzyme activity
What are the two kinds of inhibitors?
1) competitive inhibition: binds to active site and prevents substrate binding
2) allosteric site: binds to other site
3) non competitive inhibition/allosteric inhibition: change in enzyme shape that prevents substrate binding
How does feedback inhibition regulate the metabolic pathways?
- cell shuts off a pathway that is not needed to prevent waste of chemical resources
- excess intermediate or product shuts off the pathway that produced it
- allosteric inhibition/ non-competitive also helps shut off the pathway
Name the laws of thermodynamics.
1) matter and energy are conserved
2) energy cannot be created nor destroyed nor produced, but is converted
3) there is always an increase in entropy (disorder)
4) cells create ordered structures from less ordered materials; this creates disorder elsewhere
Changes in free energy (G).
1) high free energy (high potential energy)
- less stable
- greater work capacity
2) spontaneous change in free energy
- more stable
- released free energy can be harnessed to do work
3) less free energy (when closest to the ground)
- more stable
- less work capacity
Calculating free energy changes and recognizing which reaction according to the sign.
delta G = G products - G reactants
exergonic reaction: negative delta G and release of energy
endergonic reaction: positive delta G and energy input is needed
What is the enzyme’s role in chemical reactions?
- speeds up reactions by lowering the energy of activation
- delta G is not affected
- does not affect the energy
- allow molecules to absorb energy and reach the transition state
What are the different ways glucose can be broken down in exergonic reactions?
- cellular respiration
- glycolysis
- Krebs cycle
- oxidative phosphorylation
- fermentation
- anaerobic respiration
What is the role of NADH in glucose catabolism?
-shuttles electrons from glucose to the electron transport chain for use in oxidative phosphorylation
How would you describe the free energy of electrons in NADH compared to water?
NADH: electrons are at high free energy, less stable, have ability to do work
water: electrons have low free energy, more stable, because of electronegativity of oxygen
What is the difference between cellular respiration and normal breathing?
cellular respiration is at the cellular level
breathing is at the organism level
