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83 Cards in this Set

  • Front
  • Back
Aerobic Oxidation
o Stage I (cytosol)
 Glucose  Pyruvate (produces ATP and NADH)
o Stage II (mito)
 Citric acid cycle (CO2 and ATP/GTP are produced)
 NADH and FADH2 also produced, utilized as electron carriers
o Stage III (mito)
 Electron transport (O2  H2O)
 Proton motive force (proton gradient)
o Stage IV (mito)
 ATP produced and exported out of mitochondria
Photosynthesis (all in chloroplast)
o Stage 1
 Energy is absorbed w/ absorption of photon of light and transferred to electrons
o Stage 2
 Electron transport (H2O  O2), also NADPH produced
 Proton motive force (proton gradient)
o Stage 3
 ATP produced
o Stage 4
 ATP, NADPH and CO2 needed for carbon fixation
 Sugar released into cytosol
Proton Motive Force
Generated when a high concentration of protons move down their gradient, and enter the membrane through ATP synthase, allowing the production of ATP
Phosphofructokinase
is key regulatory step in glycolysis


 Activated by AMP and fructose-2,6-bisphosphate
 Inhibited by ATP and citrate
Aerobic Metabolism
o Glucose + 6O2  6CO2 + 30ATP (slow, but lots of energy)
o End product of glycolysis (pyruvate) must be converted to acetyl CoA before it can enter citric acid cycle
Anaerobic Metabolism
o In yeast (NOT mammals),
 Glucose  2ethanol + 2CO2 + 2ATP
o In muscle (mammals)
 Glucose  2lactate + 2ATP
How are the compartments of a mitochondria designed?
two compartments

o Outer membrane, innermembrane space, inner membrane, matrix
Wher does the electron transport chain take place?
inner mito membrane
Citric Acid Cycle
o PyruvateAcetyl-CoA (2NADH produced = 6ATP)
o Acetyl CoA2 cycles of CAC (2 cycles b/c 2 pyruvate give 2 acetyl-CoA) producing 6NADH, 2FADH2, 2ATP
 1FADH2 = 2ATP
 So, 18ATP + 4ATP + 2ATP = 24ATP
 Total ATP for aerobic metabolism (GlycolysisCitric Acid Cycle) = 8 + 6 + 24 = 38 ATP total
Electron Transport Chain
o Inner mito membrane impermeable to NADH and oxaloacetate
o Oxaloacetate converted to malate by malate dehydrogenase in cytosol, malate enters mito through transmembrane protein, then malate dehydrogenase converts malate to oxaloacetate w/in matrix
o Transaminase converts oxaloacetate to aspartate in matrix and back to oxaloacetate in cytosol once aspartate exits matrix into cytosol through transmembrane protein


 NADH transfers electrons to Complex I (transmembrane)
 Electrons transferred to Complex II (peripheral)
 CoQ accepts electrons from Complex I and II and transfers them to Complex III (transmembrane)
 Cytochrome c transfers electrons from Complex III to Complex IV (transmembrane)
 In Complex IV, 1 O22H2O
 At each transmembrane protein, protons are pumped out of matrix, establishing a proton gradient
 For each pair of electrons that flow from NAHD to O2, 10 protons are translocated across the inner mito membrane
Chemiosmosis
the demonstration that ATP synthesis depends on a pH gradient across a membrane


o Bacteria, mitochondria and chloroplasts all use chemiosmosis to synthesize ATP; ATP synthases are similar in all 3
o ATP synthesis always occurs on cytosolic face of membrane (aka: ATP pumped into bacterium, into matrix and into stroma


o Proton movement through ATP synthase allows for exchange of ADP for ATP
o FoF1 of ATP synthase located on inner mitochondrial membrane
Photosynthesis
 Photon of light strikes light harvesting complex (LHC) and PSII, also, O2 formed from water in PSII
 All complexes found in thylakoid membrane
o Chlorophyll a and b absorbed b/t 400 and 500nm, which are the primary photosynthetic pigments in plants
o Carbon Fixation
 Catalyzed by RUBP carboxylase (Rubisco)
 Occurs in stroma
 In Calvin cycle, 3-phosphoglycerate converted to glyceraldehydes-3-phosphate, which is then transported into cytosol and converted to sucrose
 Rubisco catalyzes first step in CO2 fixation and photorespiration
Extracellular signal molecules
include proteins, peptides, steroids (lipophilic molecules), catecholamines, gases and physical stimuli (light)
Endrocrine
hormones secreted into bloodstream, targeting distant cells
Paracrine
target neighboring cells; neurotransmitters and growth factors
Autocrine
cell responds to self; growth factors (in tumors)
Receptor Activation
o Signal binds to receptor on target cell, causing a conformational change in receptor, which initiates a specific sequence of reactions
Kd
measures the affinity of a receptor for its ligand; it is the required concentration of a ligand to bind to half of the surface receptors
How does a maximum affinity occur?
hyperbolic graph plateau’s at highest point on y-axis
How can expression assays can be used to identify cDNA clones?
• Cell has receptor for ligand other than X
• Add ligand X
• If ligand X does not bind, there is no cellular response
• Transfect the target cell with a cDNA expression vector, which allows binding of ligand X, allowing for a normal cellular response
G-Protein- GTP-bound
on
G-Protein- GDP-bound
off
G-Protein switch I contains:
threonine residue
G-Protein switch II contains:
glycine residue
G-protein coupled receptors
multipass integral membrane proteins (7 membrane spanning helices)
Where do G-Protein interactions occur?
on the cytosolic side
Second Messengers of Cell Signaling
o cAMP – activates protein kinase A
o cGMP – activates protein kinase G and opens cation channels in rod cells
o DAG – activates protein kinase C
o IP3 – opens calcium channels in ER
cAMP
activates protein kinase A
cGMP
activates protein kinase G and opens cation channels in rod cells
DAG
activates protein kinase C
IP3
opens calcium channels in ER
Activation of Effector Proteins
activated receptor triggers dissociation of G-alpha from trimer, GTP binds to G-alpha activating G-alpha so it binds to an effector, once bound effector is activated
• Once hormone released from receptor, GTP bound to G-alpha is hydrolyzed and Gprotein is again inactive
What happens in slime molds when cAMP is added?
addition of cAMP leads to activation of G proteins and yellow fluorescence is decreased
o Slime molds use cAMP as signals when food is scarce
What happens during slowing contractions of the heart muscle?
o Activation of acetylcholine receptor in heart muscle cells slows contraction of heart muscle
o Once activated, G-alpha binds GTP and it is G-beta/gamma that binds to K+ channel directly, opening it and inducing a membrane potential (neg charge inside cell)
Rhodopsin
light receptor in rod cells; located in outer segment, flattened rods

absorbs photon of light, causing a conformational change in opsin, activating it
Transducin (Gt)
trimeric Gprotein coupled to rhodopsin
What happens during the perception of light?
 Opsin activated by light, activated opsin binds Gt-alpha-GDP, which activates it so GTP binds to Gt-alpha
 Gt-alpha activates phophodiesterase, converting cGMP to GMP
 Low cGMP = closing of ion channels (hyperpolarization), light is perceived
Pathway for activation of protein kinase A
o ligand binds, activating trimeric G protein, activating adenylyl cyclase, leading to cAMP synthesis
o cAMP activates cAMP-dependent protein kinase, leading to phosphorylation of target proteins
o cAMP binds regulatory subunits of protein kinase A, catalytic units dissociate and protein kinase A is active
increased cAMP
glycogen is degraded and phosphoprotein phosphatase prevented from dephosphorylatin activated enzymes
decreased cAMP
glycogen synthesis promoted
How are DAG and IP3 created?
o Active Gprotein (GTP-bound) activates phospholipase C, which cleaves phosphotidyl inositol (PIP2) to DAG and IP3
DAG and IP3
second messengers that function in elevating cytosolic calcium levels and activating protein kinase C
Why is insulin secreted from the pancreas?
in response to high blood glucose
Where is the calcium released from when cytosolic calcium levels are elevated?
Calcium released from ER into cytosol
How are transcription factors activated and what results from activation in eukaryotes?
via extracellular signals, resulting in regulated gene expression in eukaryotes
What do changes in gene expressions affect?
cell division, differentiation, cell-cell communication and immune response
What happens when transcription factors bind to regulatory sites?
turns on transcription of genes regulated by those sites
TGF-beta signaling pathway
o TGF-beta binds to type III receptor, transcription of plasminogen activator inhibitor occurs
o NLS (nuclear-localization signal) required to transport Smad complex into nucleus, so transcription can occur
Ras/MAP kinase pathway
o Activated by ligand binding to receptor tyrosine kinases
o Ras is a monomeric Gprotein
o MAP kinase enters nucleus and phosphorylates many transcription factors important in cell cycle and differentiation

o Active Ras and active MAP kinase turn on target genes via phosphorylation of transcription factors
Receptor Tyrosine Kinase
o Extracellular part binds ligand, receptor forms dimer
o RTKs phosphorylate each other on tyrosine residues on interior region of receptor (in cytosol)
GPCR (Gprotein coupled receptor)
a multipass transmembrane protein w/ 7-membrane spanning domains


o Ligand binding to Gs protein-coupled receptor results in activation of CREB transcription factor
Wnt Signaling Pathway
controles brain development, limb patterning and organogenesis
o Also controls formation of osteoblasts in humans, affecting bone desity
Hedgehog signaling pathway
o Acts through smoothened and patched proteins and contains Cubitis interruptus transcription factor (Ci)
o w/ a hedgehog, Ci is in activating form
o w/out a hedgehog, a repressing Ci fragment is generated
NF-KB Signaling Pathway
o In nucleus, NF-KB activates transcription of gene encoding I-KB-alpha, which terminates signaling and genes encoding inflammatory cytokines, which promote signaling
Notch/Delta Signaling Pathway
o Delta and Notch interact w/ transcription factors, affecting expression of genes that influence determination of cell fate during development
What is the function of Cell adhesion molecules (CAMs)?
bind to CAMs on adjacent cell
Cell-Cell Adhesions
o Cell adhesion molecules (CAMs) bind to CAMs on adjacent cell
Cell-Matrix Adhesions
o Adhesion receptors bind components of ECM
4 Families of Cell Adhesion Molecules
o Cadherins, w/ calcium binding sites
o Ig-superfamily CAMs, w/ Ig domain
o Integrins, w/ fibronectin
o Selectins, w/ lectin domains
What does blocking function of ECM proteins?
blocks development
What does blocking fibronectin w/ antibodies do?
blocks branching during morphogenesis in mouse tissues
What does blocking collagen or perlecan gene activity do?
results in defects in cartilage and bone development
How are epithelial cells held together?
o Held together by anchoring junctions and tight junctions
Anchoring Junctions
interact w/ adapter proteins and cytoskeleton
Adherens junctions
connect connect lateral membranes, interact with a belt of actin and myosin filaments, internally bracing the cell
Desmosomes
connect lateral membranes, spot-welds cells together - transfer shear forces to the epithelium as a whole, strengthening it
Hemidesmosomes
mostly on basal surface, connecting epithelium to extracellular matrix - also transfer shear forces
Tight junctions
adhesion proteins connect cells, interact with adapter proteins, connect to the cytoskeleton. Control flow of solutes through extracellular spaces between cells.
Gap junctions
allow diffusion of small water-soluble materials between adjacent cells.
Cadherin
allows clumping of cells due to presence of calcium
ECM in bone
calcified
ECM in cartilage
flexible
ECM in connective tissue
fibroblasts
4 protein components of the basal lamina
 Type IV collagen
 Laminin
 Entactin
 Perlecan
How is collagen structured?
Collagen has triple helix w/ glycine sidechains in the middle of the helix for flexibility; globular domains interact head-to-head
What is the structure of Laminin?
Laminin has 3 chains linked by S-S bonds
Synthesis of fibrillar collagens
Procollagen associates to form collagen fibril w/ cross striations
Why is fibornectin important?
Fibronectin structure is important in wound healing and cell development
How are multiple forms of fibronectin formed?
Fibronectin has many forms generated by alternative splicing of mRNA
What do integrins link?
Integrins link fibronectin and the cytoskeleton
Cell Migration
 Selectin ligand on leukocyte binds to P-selectin on endothelial cell
 Active integrin binds to ICAM-2, resulting in extravasation
structural components of plant cell wall
o Pectin (polysaccharides)
o Cellulose microfibril
o Hemicellulose
o Plasmodesmata – junctions in plant cell walls
Plasmodesmata
junctions in plant cell walls