Shared Flashcard Set

Details

Biochem Exam II
Enzymes, Kinetics, Membranes, Lipids, Glycolysis - Dr. Brown FGCU
140
Biology
Undergraduate 4
03/25/2010

Additional Biology Flashcards

 


 

Cards

Term
Apoenzyme
Definition
An enzyme without its cofactor
Term
Holoenzyme
Definition
Cataclytically active enzyme
Term
A reaction can take place spontaneously only if ΔG is - or +?
Definition
Negative
Term
Transition state
Definition
Least stable and most-seldom-occurring species along the reaction pathway
Term
Active site
Definition
The region of the enzyme that binds the subtrates and cofactor
Term
Michaelis-Menten equation
Definition

V0=Vmax x [S]/[S]+KM

 

KM=k-1+k-2/k1

Term
An alcohol reacts with a ketone to form an ___?
Definition
Intramolecular hemiketal
Term
An alcohol reacts with an aldehyde in carbohydrates to form an ___?
Definition
Intamolecular hemiacetal
Term
α (alpha) designation of a cyclic carbohydrate
Definition
The hydroxyl group on the anomeric carbon points in the opposite direction as the hydroxyl group on Carbon 2
Term
β (beta) designation of cyclic carbohydrate
Definition
The hydroxyl group on the anomeric carbon points in the same direction as the hydroxyl group on Carbon 2
Term
N-glycosidic bond
Definition
The anomeric carbon atom of a sugar is linked to the nitrogen atom of an amine
Term
1,4-glycosidic bond
Definition
Bond between C1 of one sugar and C4 of another
Term
Glycosyltransferase
Definition
Enzyme which catalyzes the formation of glycosidic bonds
Term
Disaccharide
Definition
Consists of two sugars joined by an O-glycosidic bond
Term
Glycogen
Definition
The most common homopolymer in animal cells; the storage form of glucose
Term
Starch
Definition
Storage form of glucose in plant cells
Term
Difference between α and β 1,4 linked polysaccharide structure
Definition

alpha -- favor bent structures, which are more suitable for storage (starch & glycogen)

 

beta -- favor straight chains, which are optimal for structural purposes (cellulose)

Term
Proteoglycan
Definition
Proteins attached to a specific polysaccharide called glycosaminoglycan
Term
Fuctions of proteoglycan (4)
Definition

1) Lubricants in connective tissue

2) Structural component in connective tissue

3) Mediate adhesion of cells to extracellular matrix

4) Bind factrs that stimulate cell proliferation

Term
Glycoprotein
Definition
Carbohydrates connected to proteins
Term
Protein residues to which carbohydrates bind
Definition
Aspargine, serine, or threonine
Term
Advantage of varying blood types in humans (ABO)
Definition
Prevents mimicry of human carbohydrate structure by pathogenic microorganisms
Term
Lectins
Definition
Carbohydrate-binding proteins which facilitate cell-to-cell contact
Term
Lipids
Definition
Water-insoluble molecules that are highly soluble in organic solvents
Term
Free fatty acids
Definition
Simplest type of lipid; most commonly used as a fuel
Term
Triacylglycerols
Definition
Storage form of fatty acid
Term
Phospholipids
Definition
Membrane lipids consist of fatty acids attached to a scaffold that also bears a charged phosphoryl group, creating a macromolecule with a polar head and nonpolar tail
Term
Glycolipids
Definition
Bound to carbohydrates and are important membrane constituents
Term
Steroids
Definition
Polycyclic hydrocarbons that function as hormones that control a variety of physiological functions
Term
ω carbon atom in fatty acids
Definition
Last carbon in the carbon chain that is always a methyl group
Term
Configuration of most double bonds in fatty acids
Definition
cis
Term
Presence of cis double bond in fatty acid does what?
Definition
Kinks the hydrocarbon chain and makes tight packing between the chains impossible
Term
Problem with trans fats
Definition
Trans double bond configuration allows for tight packing of hydrocarbon chains and can cause rigidity
Term
[image]
Definition
Fatty acid
Term
[image]
Definition
Triacylglycerol
Term
Triacylglycerols
Definition
Three fatty acids attached to a glycerol molecule; fatty acid storage
Term
Bond by which glycerol and fatty acids are joined in triacylglycerols
Definition
Ester
Term
Fat storage vs carbohydrate storage
Definition
1g fat stores 6x more energy than 1g carbohydrates
Term
Adipose tissue
Definition
Major accumulation of triacylglycerols
Term
Four components of a phospholipid
Definition

1) One or more fatty acids

2) A platform to which the fatty acids are attached (glycerol or sphingocine)

3) A phosphate

4) Alcohol attached to the phosphate

4)

Term
Phosphoglyceride
Definition
Phosphlipids derived from glycerol
Term
[image]
Definition
Sphingosine; an 18-carbon amino alcohol unsaturate hydrocarbon chain
Term
Sphingolipids
Definition
Phospholipids built on a sphingosine backbone
Term
Sphingomyelin
Definition
Common sphingolipid found in membranes, especially in the myelin sheath surrounding nerve axons 
Term
Glycolipids
Definition
Sugar-containing lipids found in animal cell membranes with unknown function; derived from sphingosine
Term
Cerebroside
Definition
Simplest glycolipid containing a single sugar residue, either glucose or galactose
Term
Ganglioside
Definition

Complex glycolipid that contains branched chains of sugar residues (up to 7)

 

 

Term
Glycolipid orientation
Definition
Asymmetric orientation in membranes with sugar residues on the extracellular side of the membrane
Term
Steroid structure
Definition

Tetracyclic ring structure: steroid nucleus

Three cyclohexane rings and a cyclopentane ring joined together

Term
Membrane composition of archaea
Definition

Fatty acid chaines joined to glycerol by ether linkages (rather than ester)

 

Alkyl chains are branched rather than linear

Term
Amphipathic molecules
Definition
Contain both hydrophobic and hydrophilic regions (membrane lipids)
Term
Integral membrane proteins
Definition
Proteins embedded in the hydrocarbon chains of membrane lipids
Term
Peripheral membrane proteins
Definition
Proteins that are primarily bound to the head groups of the lipids in the cell membrane
Term
Bacteriorhodopsin
Definition
Uses light energy to transport protons from inside the cell to the outside, generating a proton gradient used to form ATP
Term
Polarity of membrane spanning alpha helices
Definition
Largely nonpolar
Term
Bacterial porin
Definition
Composed mostly of beta strands that create a single beta sheet which curls to form a hollow cylinder (pore)
Term
Polarity of porin
Definition

Outside surface of porin is nonpolar (interacts with membrane)

 

Inside surface is hydrophilic (interacts with water)

Term
Lateral diffusion in lipid membranes
Definition
The rapid lateral movement of membrane proteins which has been visualized with the used of fluorescence microscopy and photobleaching
Term
Rate of lateral movement
Definition
2 μm per 1 second
Term
Transverse diffusion of lipid molecules
Definition
Flip-flopping of lipid molecules; once in several hours (very slow)
Term
Key modulator of membrane fluidity in animals
Definition
Cholesterol
Term
Cholesterol in lipid membranes
Definition
Disrupts the tight packing of fatty acid chains
Term
Two factors which determine whether a small molecule will cross a membrane
Definition

1) The concentration gradient of the molecule across the membrane

 

2) The molecule's solubility in the hydrophobic environment of the membrane

Term
Na+ K+ ATPase -- How does it work?
Definition
The hydrolysis of ATP by the pump provides the energy needed for the active transport of three Na+ ions out of the cell and two K+ ions into the cell, generating the gradients; ATP-driven pump
Term
Antiporter
Definition
Couple the downhill flow of one species to the uphill flow of another in the opposite direction across the membrane
Term
Symporter
Definition
Use the flow of one species to drive the flow of a different species in the same direction across the membrane
Term
Secondary transport
Definition
Membrane proteins that pump ions or molecules uphill by coupling with the downhill flow of a different molecule
Term
Example of secondary transport -- Na+/K+ & Na+/glucose
Definition
The antiporter Na+Ka+ ATPase pumps 3 Na+ ions out and 2 K+ in by hydrolyzing ATP. The Na+ gradient on the outside of the cell drives the Na+/glucose symporter to bring Na+ and glucose into the cell
Term

Potassium selectivity filter function/mechanism

 

Definition
Potassium gives up its hydration shell to interact with the oxygen atoms of the carbonyl groups of the 5 amino acid residues. Energy cost of dehydrating K+ is made up by the interactions with the selectivity filter, so dehydration is favorable
Term
Why can't Na+ fit through K+ channel?
Definition
The high energetic cost of dehydrating Na+ ions would not be recovered. The K+ channel does not closely interact with the sodium ions, which must stay hydrated and hence cannot pass through the channel
Term
Pepsin
Definition
Proteolytic enzyme in the stomach
Term
Pancreatic secretion of NaHCO3
Definition
Neutralizes the pH of the food as it leaves the acidic stomach and enters the small intestine
Term
Zymogen or proenzyme
Definition
Inactive precursor to enzyme
Term
Secretin
Definition
Released by the cells of the small intestine in reponse to the low pH of the food
Term
Cholecystokinin (CCK)
Definition
Hormone secreted by the cells of the small intestine in response to the oligopeptide products of pepsin digestion
Term
Enteropeptidase
Definition
Activates trypsinogen into trypsin, which activates the remaining pancreatic zymogens
Term
α-amylase
Definition
Digests branched holopolymers of glucose (starch & glycogen) by cleaving the α-1,4 bonds, but not the α-1,6
Term
Emulsion
Definition
Combination of lipid droplets and water that leaves the stomach
Term
Lipases
Definition
Enzymes secreted by the pancreas which degrade triacylglycerids into fatty acids and monoacylgycerol
Term
Micelles
Definition
The structure in which free fatty acids and monoacylglycerol is carried to the intestinal epithelium and absorbed across the plasma membrane
Term
Chylomicrons
Definition
Lipoprotein transport particles that are formed then triacylglycerides are resynthesized from fatty acids and the monoacylglycerol in the mucosal cell. They are released into the lymph system.
Term
ATP structure
Definition
Adenine nucleotide, a ribose, and a triphosphate unit (two phosphoanhydride bonds)
Term
Phosphoanhydride bond formation
Definition
Forms between two phosphoryl groups accompanied by the loss of a molecule of water
Term
ATP hydrolysis
Definition
Free energy is released when ATP is hydrolyzed to ADP/Pi or AMP/PPi
Term
Factors affecting high phosphoryl transfer potential (3)
Definition

1) Electrostatic repulsion is reduced when ATP is hydrolyzed

2) ADP and Pi have greater resonance stability than ATP

3) More water can bind to ADP than ATP; hydration stabilizes the molecule

Term
Amount of ATP present in human vs amount consumed in 24 hours
Definition
100g present, 40 kg consumed
Term
Carbon dioxide vs methane -- which has more energy?
Definition
Methane - the more reduced carbon contains more energy. Fats are more efficient fuel source than carbohydrates because they are more reduced
Term
Energy of oxidation
Definition

Trapped as high phosphoryl transer potential compound, then used to form ATP.

 

1,3-BPG + ADP --> 3PG + ATP

Term
NAD+
Definition

Nicotinamide adenine dinucleotide - major electron carrier in oxidation of fuel molecules

 

Derived from niacin

 

R-CHOH-R' + NAD+ <---> R-C=O-R' + NADH + H+

Term
FAD
Definition

Flavin adenine dinucleotide in its oxidized form

 

Consists of riboflavin & ADP unit

 

Reduced forms: FADH2

 

R-CH3-CH3-R' + FAD <---> R-CH=CH-R' + FADH2

Term
Reductive biosynthesis
Definition
Reducing power is needed in addition to ATP to form the product
Term
CoA carries ___?
Definition
Acyl groups
Term
Reactive site of CoA
Definition

Terminal sulfhydryl group

 

Acyl groups are linked to the sulfhydryl group by thioester bonds

Term
Pantothenate
Definition
CoA vitamin precursor
Term
Riboflavin (vitamin B2)
Definition
FADH2 vitamin precursor
Term
Niacin
Definition

B3

 

NADH & NADPH vitamin precursor

Term
Thiamine
Definition

B1

 

Coenzyme: thiamine pyrophosphate (TPP)

Term
Biotin
Definition
ATP-dependent carboxylation and carboxyl-group transfer
Term
Folic acid
Definition
Thymine synthesis
Term
Irreversible reactions of glycolysis
Definition
1, 3, 10
Term
Glycolysis equation
Definition
C6H12O6 + 6O2 --> 6CO2 + 6H2O + 2805 kJ/mol
Term
Importance of Reaction 3 of glycolysis
Definition
Product (G6P) can only be used for glycolysis so all of this product is funneled into this pathway
Term
Steps of glycolysis ATP spent/ gained
Definition

Steps 1 & 3 -- 2 ATP spent

Steps 7 & 10 -- 4 ATP gained

 

2 ATP total gained

 

Term
Energy charge
Definition

Ratio of ATP: AMP

 

High energy charge if [ATP] > [AMP]

Low energy charge if [ATP] < [AMP]

Term
PFK as key regulatory step of glycolysis
Definition

Citrate is the first product of the citric acid cycle and inhibits PFK

 

Citric acid cycle is more efficient and produces more ATP than glycolysis, so if this system is running glycolysis is unneccessary.

Term
High concentration of ___ inhibits phosphofructokinase, pyruvate kinase, & hexokinase by allosterically binding to the enzymes
Definition
ATP
Term
Hexokinase function
Definition
Phosphorylates C6 of glucose
Term
Phosphoglucose isomerase function
Definition
Converts glucose into fructose (aldose to ketose)
Term
Phosphofructokinase function
Definition
Phosphorylates F6P into 1,6-BP
Term
Aldolase function
Definition
Cleaves 1,6-BP into DHAP & GAP
Term
Triose phosphate isomerase function
Definition
Converts DHAP into GAP (ketone to aldehyde)
Term
Glyceraldehyde 3-phosphate dehydrogenase function
Definition
Phosphorylates the carbonyl carbon of GAP
Term
Phosphoglycerate kinase function
Definition
Removes phosphoryl group from carbonyl carbon, leaving a carboxylic acid
Term
Mutase function
Definition
Shifts phosphoryl group to C2 and hydroxyl group to C3 (3-PG to 2-PG)
Term
Enolase function
Definition
Dehydrates 2-PG to enol (phosphoenolpyruvate -- PEP)
Term
Double reciprocal plot
Definition
Lineweaver-Burk
Term
KM
Definition

Michaelis constant -- unique to each enzyme ad is independent of enzyme concentration

 

Describes the properties of enzyme-substrate interaction and will vary if an enzyme uses several substrates

Term
Competetive inhibition double reciprocal graph
Definition
Lines representing presence & absence of inhibitor will have the same y-intercept
Term
Noncompetetive inhibition double reciprocal graph
Definition
Lines will have the same x-intercept
Term
Induced fit
Definition
Binding model for enzyme and substrate where enzyme changes shape
Term
Enzymes facilitate formation of ___?
Definition
Transition state
Term
Sigmoidal reaction plot
Definition
Allosteric enzyme
Term
Hyperbolic reation plot
Definition
Michaelis-Menten enzyme
Term
Allosteric activator
Definition
Shifts T-R equilibrium toward R state
Term
Allosteric inhibitor
Definition
Shifts T-R equilibrium toward the T state
Term
Form of inhibition can be overcome by increasing [S]
Definition
Competetive inhibition
Term
Form of inhibition that lowers [functional enzyme]
Definition
Noncompetetive inhibition
Term
Enzyme that has a large hydrophobic S1 pocket
Definition
Chymotrypsin
Term
Catalytic triad in serine proteases
Definition
Ser-His-Asp
Term
Oxyanion hole
Definition
Stabilizes tetrahedral intermediate in peptide cleavage
Term
Epimers
Definition
Two sugars that differ in stereochemistry around only 1 chiral center
Term
Anomeric carbon
Definition
New chiral center formed when cyclic hemiacetal is formed
Term
Hydropathy plot
Definition
Type of plot that can be used to predict the presence of transmembrane alpha helices
Term
Toxin that inhibits sodium channel
Definition
Tetrodotoxin (Japanese puffer fish)
Term
Active transport
Definition
Type of transport driven by the hydrolysis of ATP
Term
Amphipathic molecule
Definition
Molecule that has both hydrophilic and hydrophobic regions
Term
Lactose
Definition
Disaccharide of glucose and galactose
Term
Glucagon
Definition
Pancreatic enzym that responds to low blood sugar
Term
Isozyme
Definition
Alternate form of an enzyme
Term
Feedback inhibiton
Definition
Product of enzymatic reaction inhibits the reaction
Supporting users have an ad free experience!