Test 2 Flashcards
How do enzymes function?
By lowering the activation energy by increasing the rate of the reaction; change rate at which equilibrium is reached
What are enzymes?
Catalysts for biological reactions
How do temperature and pH affect enzymes?
Temp- as it increases so does the rate of the reaction and vice versa
pH- changing shape or charge properties or substrate so either substrate cannot bind to active site or undergo catalase
What is an enzymes active site?
The region where a substrate binds and a catalytic event occurs
What is an enzymes prosthetic group?
A small organic group of metal ions that frequently function as electron receptors
Oxidoreductases causes…
Oxidation reduction reactions
Transferases
Transfer of function groups from one molecule to another
Hydrolases
Hydrologic cleavage of
One molecule into 2 molecules
Lyases is?
Addition of a group to a molecule with a rearrangement of electrons
Isomerases
Movement of a functional group within a molecule
Ligases
Joining of 2 molecules to form a single molecule
How do enzymes bind to substrates to catalyze reactions?
Random collision, lock and key model or induced fit model
What is the cycle of events that an enzyme goes through?
Substrate binding
Substrate activation
Catalytic event
Product release
What is Vmax?
The upper limit of a reaction rate
What is Km?
Michaelis constant; a specific concentration of substrate depending on the affinity of the enzyme
What is saturation?
The relationship between the rate of reaction and concentration of substrate depending on the affinity of the enzyme
What are the four methods used in enzyme regulation?
Alteration of temp/pH Substrate level regulation Competitive inhibition Allosteric regulation Covalent modification
What is competitive inhibition?
Molecules bind to the active site so that substrates CANNOT bind
What is allosteric regulation?
Facilitated by binding of regulatory molecules at the allosteric site
What are ribozymes?
RNA molecules that act as catalysts; NOT a protein
What is covalent modification?
Enzyme activity is affected by the addition of removal of chemical groups via covalent bonding
What are the functions of membranes?
Define boundaries Loci for specific functions Transport proteins Receptors Cell-to-cell communication
What is the fluid mosaic model?
Mosaic of proteins discontinuously embedded in or attached to a fluid lipid bilayer
How was it discovered that the membrane was composed of a lipid bilayer?
The lipid bilayer membrane structure in 1925
How is cholesterol incorporated into membranes?
By being found in sterols in animal cells
What are the 3 classes of membrane lipids?
Phospholipids
Glycolipids
Sterols
What are the ways that lipids can move within the membrane?
- Rotation about their long axis
- Lateral diffusion in the plane of the membrane
- transverse diffusion requiring hydrophilic head to pass hydrophobic interior
How is lipid mobility measured?
Within membranes by fluorescence recovery after photo bleaching (occurs within seconds)
What factors affect membrane fluidity?
Sterols decrease fluidity above Tm(rigid, prevents movement)
Sterols increase fluidity below Tm(prevent phospholipids from fitting together)
What are the functions of proteins found in the membrane?
Transport
Receptors
Adhesion
What are the classes of membrane proteins?
- Integral- Cyto, exo & transmembrane domain
- Lipid anchored-one or more covalently linked lipids; GPI anchor
- Peripheral- associated with integral & lipid head groups
How can scientists visualize the mobility of membrane proteins?
- freeze fracture images
- exposure to electrical field
- mouse & human cell fusion
What are glycoproteins?
Conjugated to carbs; almost ALWAYS on exo- face
What are the functions of glycoproteins? (4)
Defense
Cellular uptake
Adhesion
Embryonic development
What is diffusion?
The movement of solutes
What is osmosis?
The movement of water across a selectively permeable membrane
What is facilitated diffusion?
The movement of diluted down the gradient mediated by proteins
What is active transport?
Moving solutes against concentration gradient
What is passive transport?
Simple/facilitated diffusion
What is indirect active transport?
One solute moving down gradient while driving the other solute up
Why is direct active transport?
Accumulation of molecules is coupled directly to an exergonic chemical reaction
What types of molecules can cross the membrane by simple diffusion?
Small, non polar molecules
How does water move during osmosis?
From low to high solutes
What type of diffusion exhibits saturation?
Facilitated diffusion
What is the difference between carrier and channel proteins?
Carrier- bonds solutes on one side of the membrane & changes the conformation which allows solutes to diffuse
Channel- forms hydrophilic channels in member and so diffusion may occur
What are three types of carrier transport proteins?
Uniport
Symport
Antiport
What is uniport?
1 solute 1 direction
What is symport?
2 solute same direction
What is antiport?
2 solutes opposite direction
How do plant and animal cells respond differently to hyper- iso- and hypotonic solutions?
Hyper- both shrivel
Iso- both are normal
Hypo- animal explodes/plant expands
What are the different types of ATPases?
P, V, F, and ABC
What is p-type?
Pumps Na, K, Ca ions; reversibly phosphorylated and found in plasma membrane
What is v-type?
Pumps hydrogen ions into the vacuole
What is f-type?
Pumps H ions using ATP hydrolysis; found in bacteria, mitochondria and chloroplasts; reversible using ATP synthase
What is ABC-type?
Pumps a variety of solutes including nutrients, proteins, is also used to pump drugs out of cells
Steps of Na/K pump? (6)
- 3 Na ions bind to a protein in the initial E1 confirmation
- Binding of the Na ions triggers the phosphorylated enzyme
- Phosphorylation results in A conformational change from E1 to E2 Na are transported in the membrane to outside the cell
- K ions outside cell bind to enzyme
- Binding of K triggers de phosphorylation and rerun to E1
- K transported through membrane to inside cell
Na/glucose pump? (6)
- 2 external Na ions bind to symporter
- Glucose is able to bind to symporter
- Conformational change of protein exposed the molecule to the inside of the cell
- Na ions released in response to low internal Na concentration
- Transporters locked in conformation until glucose is released inside cell
- Empty transporters open to outside of cell again
What is depolarization?
A change in membrane potential to a less negative value
What is hyperpolarization?
Membrane potential briefly becomes more negative than normal
What does a dendrite do?
Receives messages and sends them to other parts of the body
What does the axon do?
Conducts impulses away from the body
What is the role of the myelin sheath?
To accelerate transmission of nerve impulses
What is the nodes of ranvier?
Small segments of axon between segments of myelin sheath
What are neurotransmitters?
Chemicals released by neurons that transports impulse across a synapse
How do nerve cells respond to depolarization?
They return to resting membrane potential
How do voltage gated ion channels function?
As interval membrane proteins that form ion conducting pores who’s permeability is regulated by changes in membrane potential
What are the 3 types of voltage gated channels?
Open confirmation
Closed confirmation
Channel inactivation
What is an action potential and why are they important?
Membrane potential changing from negative to positive back to negative in response to stimulus. It is important bc it transmits signals along cell membranes.
How do action potentials travel along nerve cells?
Via Na and K channels
How do signals travel different in myelinated vs. non-myelinated nerve cells?
Myelinated travel faster and farther, non-myelinated travel in waves and take longer
What is MS?
The moss of myelin sheath due to an autoimmune response. Sodium escapes and damages nerve s which reduced communication and function
What are the 2 types of synaptic transmissions?
Electrical and chemical
What is electrical transmission?
Neurons connected by gap junctions; spread of depolarization. The signal is immediate and is 3-5 nm
What is chemical transmission?
Neurons connected by adhesion proteins; synaptic cleft 20-50 nm. Transmission requires neurotransmitters held in vesicles
Name the 4 types of neurotransmitters
Acetylcholine
Amino acids
Monoamines
Neuropeptides
What is an example of acetylcholine?
Cholinergic
What are 3 examples of amino acid neurotransmitters?
GABA, glycine, glutamine
What are 3 examples of monoamine neurotransmitters?
Nonadrenaline, dopamine, serotonin
What is an example of the neuropeptide transmitter?
Endorphins
How are neurotransmitters sent from one nerve class to another?
Exocytosis
What are the types of neurotransmitters receptors that we discussed? And details of both.
1. Nicotinic acetylcholine receptor Binds 2 molecules Ligand gated Na+ channel Depolarization 2. GABA receptor Binds to GABA ligand gated Cl- channel Hyper polarization
How are neurotransmitters inactivated?
- Reputable
2. Degradation
What is re uptake?
Neurotransmitters pumped back into presynaptic neurons
What is degradation?
Unique to acetylcholine; neurotransmitters broken down by enzymes
What are chemical signals?
Molecules that bind to receptors on target cell surface and elicit a response from target cells
What are second messengers?
Molecules produced in target cells that relay the signal from one part of the cell to the other
What are Ligands?
Small messenger molecules
What are high affinity receptors?
Ligand binds easy, low concentrations of ligand can occupy many receptors
What are low affinity receptors?
Ligand DOES NOT bind easily, high concentration of ligand required to occupy many receptors
What is auto regulation?
Internal adaptive mechanism that works to adjust that systems response to stimuli
What is apoptosis?
Clean cell death
What properties give receptors affinity and specificity for their Ligands?
Binding site shape, amino acid placement, multiple noncovalent bonds
What is the dissociation constant and how does it relate to the receptor affinity?
Kd
It indicates how much ligand is needed to trigger a response in a target cell
How do receptors adapt to prolonged exposure to Ligands?
Receptor- down regulation
How are agonists and antagonists similar and different?
Similar by both being artificial Ligands recognized by cellular receptors
Different by agonists activate endorphins and antagonists block Ligands from binding
What are the 2 types of plasma membrane receptors that were discussed
G protein linked receptors
Protein kinase associated receptors
What are G protein linked receptors?
Ligand binding causes a change in confirmation that activated a G protein
What is a protein kinase associate receptor?
Ligand binding activates causing phosphorylation events
What are the structures of the G protein linked and protein kinase associated receptors?
G protein- 3 subunits
Protein kinase- single polypeptide chain with one transmembrane domain
What are the subunits that make up G proteins?
Alpha, beta, gamma (α,β,γ)
How are G proteins activated and inactivated?
Activated by lingands bonding to receptor, receptor binding to transcription protein, protein reaches nucleus and is activated
Inactivation- Gα hydrolysis GTP, GTP to GDP, Gα reassociates with Gβγ
What is the difference between Gs and Gi proteins?
Gs- stimulatory; activated adenylate Cyclades for ^ in cAMP
Gi- inhibitory; inhibits adenylate Cyclades for decrease in cAMP
What enzyme is responsible for synthesis of cAMP?
Adenine Cyclase
How does the cell get rid of cAMP once the stimulatory ligand is no longer bound to the receptor?
Phosphodiesterase to AMP
What are 2 diseases that affect signal transduction pathways?
Cancer and diabetes
How are calcium ions utilized in signal transduction?
In apoptosis when cytochrome C is activated and released from the mitochondria, it stimulates calcium
What types of receptors do growth factors generally bind to? And what specific type does EFG bind to?
EFG; tyrosine kinase
How are tyrosine kinases activated?
Ligand binding-> clumped receptors phosphorylated each other -> auto phosphorylation
How are hormones different than other Ligands?
Hormones can act from a long distance away, Ligands must touch to react
What are the important molecules of apoptosis?
P53
Bcl2
Cytochrome C
What is the role of p53 in apoptosis?
Triggers apoptosis in response to DNA damage
What is Bcl2 in apoptosis?
Anti-apoptosis proteins found in mitochondrial surface
What is the role of cytochrome C in apoptosis?
Release from mitochondria to promote apoptosis
