Biochemistry Flashcards

Question

What is the quarternary structure of a protein?

Answer 1

- Exist for proteins that contain more than one poly peptide chain; for these proteins, the quarternary strucutre is an aggregate of smaller globular peptides, or subunits and represents the functional form of the protein

Answer 2

- Has a characteristic trihelical fiber (three α-helices woven together to form a secondary helix) - Makes up most of the extracellular matrix of connective tissue - Is found throughout the body and is important in providing strength and flexibility

Answer 3

- Intermediate filament proteins found in epithelial cells - Contribute to the mechanical integrity of the cell and also function as regulatory proteins - Primary protein that makes up hair and nails

Answer 4

a group of glycoproteins that mediate calcium-dependent cell-adhesion - cadherins often hold similar cell types together, such as epithelial cells - different cells usually have type-specific cadherins; for example, epithelial cells use E-cadherin while nerve cells use N-cadherin

Answer 5

- A group of proteins that all have two membrane-spanning chains called α and β - Chains are very important in binding to and communicating with the extraceullar matrix - Also play a very important role in cellular signaling and can greatly impact cellular function by promoting cell division, apoptosis, or other processes

Answer 6

- Bind to carbohydrate molecules that project from other cell surfaces - Bonds are the weakest formed by the cell adhesion omlcules - Expressed on white blood cells and endothelial cells - play an important role in host defense, including inflammation and white blood cell migration

Answer 7

- **G_s**: stimulates adenylate cyclase, which increases levels of cAMP in the cell - **G_i**: inhibits adenylate cyclase, which decreases levels of cAMP in the cell - **G_q**: activates phospholipase C, which cleaves a phospholipid into PIP₂, which can later be cleaved into DAG and IP₃

Answer 8

- Subjects compounds to an electric field, which moves them accoridng to their net charge and size - Negatively charged compounds will migrate toward the positively charged anode - Positively charged compounds will migrate toward the negatively charged cathode Velocity of the migration, v= Ez/f E: electric field z: net charge on the molecule f: coefficient of friction

Answer 9

- separates proteins on the basis of mass alone - SDS: a detergent that disrupts all noncovalent interactions; binds to proteins and creates large chains with net negative charges, thereby neutralizing the protein's original charge and denaturing the protein - As the proteins move through the gel, the only variable affecting the velocity is f, the frictional coefficient, which depends on mass

Answer 10

Native gels, also known as non-denaturing gels, analyze proteins that are still in their folded state. Thus, the electrophoretic mobility depends not only on the charge-to-mass ratio, but also on the physical shape and size of the protein - Most useful to compare the molecular size or charge of proteins known to be similar in size from other analytic methods like SDS-PAGE or size-exclusion chromatography

Answer 11

- Separates proteins by isoelectric point - Mixture of proteins is placed in a gel with a pH gradient - Proteins that are positively charged will begin migrating toward the cathode and proteins that are negatively charged will begin migrating toward the anode - As the protein reaches the portion of gel where the pH is equal to the protein's pI, the protein takes on a neutral charge and will stop moving

Answer 12

A method of sequencing amino acids in a peptide. In this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues. - Uses cleavage to sequence proteins of up to 50 to 70 amino acids - selectively and sequentially removes the N-terminal amino acid of the protein which can be analyzed via mass spectroscopy

Answer 13

- A spectroscopic analytical procedure used to measure the concentration of protein in a solution - It is subjective, i.e., dependent on the amino acid composition of the measured protein - In its protonated form, the dye exists as a brown-green color; the dye is deprotonated by the protein and gives up protons to the ionizable groups in the protein, turning blue in the process - Can compare the blueness of the sample to the blueness of the standard curve by measuring absorbance - Very accurate when only one type of protein is present

Answer 14

- The simplest aldose (an aldotriose)

Answer 15

Enantiomers

Answer 16

- A subtype of diastereomer; differ in configuation at exactly one chiral center

Answer 17

α-anomer: Has the -OH group of C-1 trans to the -CH₂OH substituent (axial and down) β-anomer: has the -OH group of C-1 cis to the -CH₂OH substituent (equatorial and up)

Answer 18

- When expsosing hemiacetals to water, the hemiacetal will spontaneously cycle between the open and closed form - Bcause the substituents on the single bond between C-1 and C-2 can freely rotate, either the α or β-anomer can be formed - This spontaneous configuration about C-1 is known as mutatrotation

Answer 19

-The α-anomeric configuratoin is less favored because the hydroxyl group of the anomeric carbon is axial, adding to the steric strain of the molecule

Answer 20

- A reducing sugar is any sugar that is capable of acting as areducing agent because it has a free aldehyde group or a free ketone group. - All monosaccharides are reducing sugars, along with some disaccharides, oligosaccharides, and polysaccharides **Tollen's Reagent**: uses Ag(NH₃)₂⁺ an as oxidizing agent; in a positive Tollen's test, aldehydes reduce Ag+ to metallic sivler **Benedict's reagent**: the adehyde group of an aldose is readily oxidized, indicated by a red precipitate of Cu₂O

Answer 21

Glucose-α-1,2 fructose

Answer 22

Galactose-β-1,4 glucose

Answer 23

Glucose- α-1,4-glucose

Answer 24

β-1,4 glycosidic bonds - Humans lack cellulase, so we cannot digest these types of bonds - Cellulose: main structural component of plants

Answer 25

Glucose units are linked in a linear way with α-1,4 glycosidic bonds. Branching takes place with α-1,6 bonds occurring every 24 to 30 glucose units, resulting in a soluble molecule that can be quickly degraded as it has many end points onto which enzymes can attach.

Answer 26

Glucose units are linked together linearly by α-1-4 glycosidic bonds from one glucose to the next Branches are linked to the chains from which they are branching off by α-1,6 glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain - There is approximately 1 α-1,6 glycosidic bond for every 10 glucose molecules

Answer 27

- Insolubility in water and solubility in non-polar organic solvents

Answer 28

- Head: a phosphate and alcohol - Tail: Hydrophobic fatty acid - Linked by a phosphodiester bond

Answer 29

- A molecule which has both hydrophilic and hydrophobic regions

Answer 30

- Phospholipids that contain a glycerol backbone bound by ester linkages to two fatty acids and by a phosphodiester linkage to a highly polar head - The head group determines the membrane surface properties; head groups can be positively charged, negatively charged or neutral - Example: phosphotidylcholine is a glycerophospholipid with a choline head group

Answer 31

- Have a sphingosine backbone (as opposed to glycerol, as found in glycerophospholipids)

Answer 32

- A subgroup of sphingolipids with head groups composed of sugars bound by glycosidic linkages - Cerebrosides: have a single sugar - Globosides: have two or more sugars

Answer 33

- The most complex group fo sphingolipids - Glycolipids that have a polar head composed of logiosaccharides with one or more N-acetylneuaminic acid (NANA; also called sialic acid) molecule at the terminus, and a negative charge

Answer 34

- The major class of sphingolipids that are also phospholipids - Have either phosphatidylcholine or phosphatidylethanolamine as a head group, and are thus boudn by a phosphodiester bond

Answer 35

- A class of lipids built from isoprene (C₅H₈) - Steroids are metabolic derivatives of terpenes

Answer 36

- Steroids are characterized by having four cycloalkane rings together: three cyclohexane and one cyclopenate - Steroid functionality is determined by the oxidation status of these rings, as well as the functional groups they carry

Answer 37

- 20 carbon unsaturated carboxylic acids derived from arachidonic acid, which contain one five-carbon ring - In many tissues, prostaglandins regulate the synthesis of cAMP

Answer 38

- Three fatty acids bound by ester linkages to glycerol - Usually, these fatty acids are different - They are nonpolar and hydrophic; the polar hydroxyl groups of the glycerol component and the polar carboxylates of fatty acids are bound together, decreasing their polarity

Answer 39

A, D, E and K

Answer 40

- A five-carbon sugar (pentose) bound to a nitrogenous base - Are formed by covalently linking the base to C-1' of the sugar

Answer 41

- Formed when one or more phosphate groups are attached to C'5' of nucleoside - The building blocks of DNA - Often these molecules are named according to the number of phosphates bound - Example: adenosine di- and triphosphate (ADP and ATP)

Answer 42

Ribose: -OH at the 2' position Deoxyribose: -H at the 2' position

Answer 43

- Formed as nucleotides are joined by 3'- 5' phosphodiester bonds (the phosphate group links the 3' carbon of one sugar to the 5' phosphate group of the next sugar)

Answer 44

1. Compound is cyclic 2. Compound is planar 3. Compound is conjugated (has alternating single and multiple bonds, or lone pairs, creating at least one unybridizied p-orbital for each atom in the ring) 4. The compound has 4n+2 (n is any integer) π electrons; this is known as Hückel's Rule

Answer 45

DNA in which the double helix has a left-handed rather than the usual right-handed twist and the sugar phosphate backbone follows a zigzag course - Makes a turn every 4.6 nm and contains 12 bases each turn - A high GC content or high salt cconcentration may contribute to the formation of this form of DNA

Answer 46

- Right-handed DNA - Makes a turn every 3.4 nm - Contains 10 bases within that span - Creates both major and minor grooves in the strand - This is what we think of when we think of DNA

Answer 47

- A dimer of H2A, H2B and H3 and H4 make up the core protein of a histone; 200 base pairs of DNA wrap around this protein forming a nucleosome - H1 seals off the DNA as it enters and leaves the nucleosome

Answer 48

Proteins that associate with DNA

Answer 49

- The chromatin which remains compacted during interphase - Appears dark under light microscopy - Is transcriptionally silent

Answer 50

- Dispersed chromatin - Appears light under light microscopy - Genetically active

Answer 51

- A region of DNA found in the center of chromosomes - Composed of heterochromatin, which is in turn composed of tandem repeat sequences that contain high GC-content - During cell division, the two sister chromatids can therefore remain connected at the centromere until microtubules separates the chromatids during anaphase

Answer 52

- DNA replication cannot extend all the way to the end of a chromosome, resulting in a loss of DNA - Thus, telomeres comprise the end of chromosomes via a simple repeating unit (TTAGGG); thse serve no real purpose and can be cut off - Telmoseres also have a high GC-content which creates exceptionally strong strand attractions at the end of chromosomes to prevent unraveling

Answer 53

**Eukaryotes**: many; in order to duplicate all of the chromosomes efficiently, each chromosome contains one linear molecule of dsDNA with multiple origins of replication **Prokaryotes**: single origin of replication

Answer 54

- Also known as DNA topoisomerase II - Cut both strands of the DNA helix simultaneously in order to manage DNA tangles and supercoils, using hydrolysis of ATP - Introduces negative supercoiling

Answer 55

- Once helicase opens up the dsDNA, the free purines and pyrimidines seek out other molecules with which to hydrogen bond - single-stranded DNA-binding proteins will bind to the unraveled strand, preventing both the reassociation of DNA strands and the degredation of DNA by nucleases

Answer 56

An enzyme that synthesizes short RNA sequences called primers - These primers serve as a starting point for DNA synthesis. - Since primase produces RNA molecules, the enzyme is a type of RNA polymerase - This is important because DNA cannot be synthesized de-novo, and needs another nucleic acid to "hook onto" in order begin synthesis of a new strand

Answer 57

- Repliacates mitochondrial DNA - Eukaryotic polymerase

Answer 58

- Participate mostly in DNA repair - Eukaryotic Polymerases

Answer 59

- Polymerases δ and ε - PCNA protein assembles with the polymerases to form the sliding clamp

Answer 60

- Eukaryotes: DNA polymerase δ - Prokaryotes: DNA Polymerase I

Answer 61

- Eukaryotes: DNA polymerases α and δ - Prokaryotes: DNA polymerase III

Answer 62

- Repair to the newly synthesized DNA strand during G2 phase of the cell cycle - MSH2 and MLH1 in eukaryotes and MutS and MutL in eukaryotes deteect and remove errors introduced in replication that were missed during the S phase of the cell cycle

Answer 63

- NER removes thymine dimers from the DNA, which have been induced by exposure to UV light Mechanism 1. Specific proteins scan the DNA moelcule and recognize the lesion because of a bulge in the strand 2. An excision endonuclease makes nicks in the phosphodiester backbone of the damaged strand on both sides of the thymine dimer and removes the defective nucleotide 3. DNA polymerase can then fill the gap by synthesizing in the 5' to 3' direction using the undamaged strand as a template 4. Ligase seals the strand

Answer 64

- BER repairs alterations to bases; for example, thermal energy can be absorbed by DNA and may lead to cytosine deamination, making cytosine into a uracil Mechanism 1. The affected base is recognized and removed by a glycosylase enzyme, leaving behind a apurinin/apyramidic (AP) site 2. AP site is recognized by AP endonuclease, which removes the damaged sequence from the DNA 3. DNA polymerase and DNA ligase can then fill the gap and seal it

Answer 65

- An enzyme that cleaves DNA into fragments at or near specific recognition sites within the molecule known as restriction sites - These enzymes cut at palindromic sequences, such as GAATTC - From this cut, some produce sticky ends, which are advantageous in facilitating the recombiantino fof the restriction fragment with the vector DNA

Answer 66

- Ttansgenic mice are altered by their germ line by introducing a cloned gene into a fertilized ova or into embryonic stem cells (a transgene) - If the transgene is disease-producing, the transgenic mice can be used to study the disease process from early embryonic development through adulthood

Answer 67

- In the 5' to 3' direction, synthesizing the protein from the N-terminal to the C-terminal

Answer 68

- In eukaryotes, mRNA is monocistronic, meaningt hat one mRNA molecule translates into only one protein product - In prokaryotes, mRNA is polycistronic

Answer 69

- An enzyme that attaches the appropriate amino acid onto its tRNA - It does so by catalyzing the esterification of a specific cognate amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA - In humans, the 20 different types of aa-tRNA are made by the 20 different aminoacyl-tRNA synthetases, one for each amino acid of the genetic code

Answer 70

Start codon: AUG Stop codons: UAA, UGA, UAG

Answer 71

- There genetic code incldues 64 codons which code for 61 acids, and three are stop signals. - Although each codon is specific for only one amino acid (or one stop signal), the genetic code is described as degenerate, or redundant, because a single amino acid may be coded for by more than one codon.

Answer 72

- A mutation in which one amino acid substitutes for another

Answer 73

- A mutation where the codon now encodes for a pemature stop codon (also known as truncation mutation)

Answer 74

- Located in the nucleolus and synthesizes rRNA - Eukaryotic RNA polymerase

Answer 75

- Located in the nucleus and synthesizes hnRNA (pre-processed mRNA) and snRNA - Eukaryotic RNA polymerase - Binds to TATA box (located at -25)

Answer 76

- Located in the nucleus and synthesizes tRNA and some rRNA - Eukaryotic RNA polymerase

Answer 77

- Added to the 3' end of the mRNA transcript and protects the message against rapid degredation; as soon as the mRNA leaves the nucleus, it will start to get degreaded from the 3' end

Answer 78

- A ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. - The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon.

Answer 79

**_A site:_** - Holds the incoming aminoacyl-tRNA complex - This is the next amino acid that is being added to the growing chain, and is determined by the mRNA codon within the A site **_P site:_** holds the tRNA that carries the growing polypeptide chain - It also is where the first amino acid (methionine) binds because it is starting the polypeptide chain - Peptidyl transferase, an enzyme that is part of the large subunit of the ribosome, passes the peptide bond from the tRNA in the P site to the tRNA in the A site **_E site:_** - where the uncharged (lacking an AA) tRNA pauses transiently before exiting the ribosome

Answer 80

- When any of the three stop codons moves into the A site, a protein called release factor binds the termination codon, causing a water molecule to be added to the polypeptide chain - The addition of this water moleucle allows peptidyl transferase and termination factors to hydrolyze the completed polypeptide chain from the final tRNA - The polypeptide chain will then be relased from the tRNA in the P site and the two ribosomal subunits will dissociate

Answer 81

- A system in which the repressor is tightly bought to the operator system and thereby acts as a roadblock - To remove the block, and inducer must bind the repressor so that the RNA polymerase may move down the gene - Example: Lac Operon; used when glucose (the preferred sugar) is low and lactose (a more energentically expensive product to digest) is high

Answer 82

CAP is a transcriptional activator used by E. coli when glucose levels are low to signal that alternative carbon sources should be used - Falling levels of glucose cause an increase in cAMP, which binds to CAP; this induced a conformational change in CAP that allows it to bind the promoter region of the operon, further increasing transcription of the lactase gene

Answer 83

- Allow constant production of the protein product - The repressor is made by the regulator gene is inactive until its bound by a corepressor; this complex then binds the operator site and prevents further transcription - Serve as negative feedback loops; often, the final strucutral product can serve as a corepressor Example: trp operon - When tryptophan is high in the local environment, it acts as a corepressor; the binding of two molecules of of tryptophan causes the repressor to bind the operator site; thus, the cell turns off its machinery to synthesize its own tryptophan, which is an energetically expensive process because its available in the environment

Answer 84

Transcription factors: a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. - Two domains: A DNA-binding domain and an activation domain - DNA binding domain: binds to a specific nulceotide sequence in the promoter region or to a DNA response element (a sequence of DNA that binds only to specific transcription factors) - Activation domain: allows for the binding of several transcription factors and other important regulatory rotein, such as RNA polymerase and histone acetylases, which function in the remodeling of DNA

Answer 85

- Acetylation of histone proteins decrease the positive charge on lysine residues and weakens the interaction of the histone with DNA, resulting in an open chromatin conformation that allows for easier access of the trascriptional machinery to DNA

Answer 86

- Lipids can also move between the membrane layers, but this is energetically unfavorable because the polar head group of the phospholipid must be forced through the nonpolar tail region in the interior of the membrane - Thus, flipases, specialized enzymes, assist in the transition or "flip" between layers

Answer 87

The plasma membranes of cells contain combinations of glycosphingolipids and protein receptors organised in glycolipoprotein microdomains

Answer 88

- Transmembrane proteins: pass completely through the membrane - Embedded proteins: associated only with the interior (cytoplasmic) or exterior (extracellular) surface of the cell - Membrane-associated (peripheral) proteins: may be bound through electrostatic interactions with the lipid bilayer, or to other transmembrane proteins

Answer 89

- Allow for direct cell-to-cell communication - Are formed by the alignment and interaction of pores composed of 6 molecules of connexin - Permit movement of water and some solutes idrectly between cells - Proteins are generallyn not transferred through gap junctions

Answer 90

- Multiprotein junctional complex whose general function is to prevent leakage of transported solutes and water and seals the paracellular pathway. - To be effective, tight junctions must form a continuous band around a cell, otherwise fluid could leak through the spakes between tight junctions

Answer 91

- Bind adjacent cells by anchoring to their cytoskeletons - Desmosomes are formed by interactions between transmembrane proteins associating the intermediate filaments inside adjacent cells - Primarily found at the interface between two layers of epithelial tissue - Hemidesmosomes: have a similar function, but hteir main function is to attach epithelial cells to underlying (basement) membranes

Answer 92

- The endocytosis of fluids and dissolved particles

Answer 93

Used in cell membrane physiology to determine the reversal potential across a cell's membrane, taking into account all of the ions that are permeant through that membrane. P: permability for the relevant ion Note: chloride is reversed because of the negative charge on a chloride ion

Answer 94

5.6mM (Range: 4-6mM)

Answer 95

- Low affinity transporter in hepatocytes and pancreatic cells - Captures excess glucose primarily for storage - When the glucose drops below the K_m (K_m≈15mM) for the transporter, much of the remainder leaves the liver and enters the peripheral circulation - GLUT2, along with glucokinase, serves at the glucose sensor for insulin release

Answer 96

- Located in adipose tissue and muscle - The rate of glucose transport in these two tissues is increased by insulin which stimulates the movement of additional GLUT4 transporters to the membrance by a mechanism involving exocytosis - K_m of GLUT4 (K_m~5mM) is close to the normal glucose levels of blood; this means that the transporters are saturated when blood glucose levels are just slightly higher than normal

Answer 97

- Skeletal muscle where there is no oxygen - RBCS, where there are no organelles

Answer 98

- The enzymes in the first step of glycolysis - Hexokinase and glucokinase take glucose and convert it to glucose 6-phosphate * *_Hexokinase_** - Present in most tissues - Low Km (reaches maximum velocity at low glucose concentration - Inhibited by glucose-6-phosphate **_Glucokinase_** - Present in heaptocytes and pancreatic β islet cells (along with GLUT 2, acts as the glucose sensor) - High Km (acts on glucose proportionally to its concentration) - Induced by insuln in hepatocytes

Answer 99

- The rate limiting enzyme and main control point in glycolysis - Converts fructose-6-phosphate to fructose-1,6-bisphosphate - Inhibited by ATP and citrate - Activated by AMP

Answer 100

- This process occurs in hepatocytes - Insulin stimulates PFK-1, indirectly - Glucagon inhibits PFK-1, indirectly - Insulin activates PFK-2 converts a tiny bit of Fructose 6-phosphate to fructose 2,6 bisphophate - F2,6BP activates PFK-1 - Glucagon inhibits PFK-2, lowering F2,6BP and thereby inhibiting PFK-1

Answer 101

- Catalyzes an oxidation and addition of of inorganic phsophate to its substrate, glyceraldehyde-3-phosphate, resulting in the production of a high-energy intermediate: 1,3 bisphosphoglycerate - Also takes NAD+ and makes NADH

Answer 102

- Transfers the high-energy phosphate from 1,3 phosphoglycerate to ADP, forming ATP and 3-phosphoglycerate - This is a substrate-level phosphorylation and produces energy in a non-oxygen dependent way - This is the only means of ATP generation in an anaerobic tissue

Answer 103

- The last enzyme in aerobic glycosis - Catalyzes substrate level phosphorylation of ADP to ATP by converting phosphoenolpyruvate to pyruvate - Pyruvate Kinase is activated by PFK-1 (a feed-forward activation); the product of an earlier reaction of glycolysis stimulates, or prepares a later reaction in glycolysis

Answer 104

- Lactate dehydrogenase: oxidizes NADH to NAD+, replenishing the coenzyme for glyceraldehyde-3-phosphate - Without mitochondria and oxygen, glycolysis would stop when all the available NAD+ had beed reduced to NADH; by reducing pyruvate to lactate and re-creating NAD+, lactate dehydrogenase prevents this potential problem

Answer 105

- In yeast, fermentation covnerts pyruvate (three carbons) to ethanol (two carbons and carbon dioxide (one carbon) - In people, fermentation converts pyruvate (three carbon) into lactate (also three carbon)

Answer 106

- Used in hepatic and adipose tissue for triacylglycerol synthesis - Is formed from fructose 1,6 bisphosphate, which can be isomerized to glycaldehyde-3-phosphate, which can then be broken down into glycerol

Answer 107

- Glucokinase and hexokinase - PFK-1 - Pyruvate kinase

Answer 108

- The enzyme that converts 1,3BPG (from glycolysis) to 2,3 bisphosphoglycerate - 2,3 BPG binds allosterically to the β-chains of hemoglobin A and decreases its afinity for oxygen

Answer 109

- Glycogen synthase; forms the α-1,4 glycosidic bond found in the lienar glcuose chains of the granule - Stimulated by: glucose-6-phosphate and insulin - Inhibited by: epinephrine and glucagon

Answer 110

- Responsible for introducing α-1,6 linked branches into the graule as it grows - Branching enzymes hyrolyzes one of the α-1,4 bonds to release a block of oligoglucose, when is then moved and added in a slightly different location - Forms an α-1,6 bond to create a branch

Answer 111

- Glycogen phosphorylase: breaks α 1,4 glycosidic bonds, releasing glucose-1-phosphate - Cannot break α-1,6 bonds and therefore stops when it nears the outermost branch point - Activated by glucagon in the liver and by AMP and epinephrine in the muscle - Inhibited by ATP - Note: a phosphorylase breaks a bond using inorganic phosphate

Answer 112

- A two-enzyme complex that deconstructs the branches in glycogen that have been exposed by phosphorylase - First, it takes the remainder of the straight chain which cannot be hydrolyzed by phosphorylase to the end of a straight chain; this leaves one glucose attached at a α-1,6 branch - Then, it hydrolyzes the single glucose from the former branch

Answer 113

- Glycerol 3-phosphate (from stored fats or traiacylglycerols in adipose tissue) - Lactate (from anaerobic glycolysis) - Glucogenic amino acids (from muscle proteins, like alanine)

Answer 114

- An enzyme in gluconeogenesis - Converts oxaloacetate to phosphoenolpyruvate (PEP) in a reaction requiring GTP - PEP cotinues in the pathway to fructose 1,6 bisphosphate; thus, phosphoenolpyruvate carboxykinase and pyruvate carboxylase reverses the irreversible actions of pyruvate kinase

Answer 115

- Fructose-1,6-Bisphosphatase - Reverses the action of phosphofructokinase-1, the rate-limiting step of glycolysis - Hydrolyzes a phosphate from fructose-1,6-bisphosphate to produce fructose-6-phosphate - Activated by ATP - Inhibited by Fructose 2,6 bisphosphate

Answer 116

- An enzyme in gluconeogenesis - First step in gluconeogenesis; takes pyruvate and makes oxaloacetate - This step occurs in the mitochondria - Note: oxaloacetate cannot leave the mitochondria so it gets turned into malate, which leaves, and once in the cytoplasm, malate gets turned back into oxaloacetate - Activated by acetyl-CoA, indicating that we have enough energy, do not need to go through the citric acid cycle and instead should rebuild sugars

Answer 117

- An enzyme in gluconeogenesis - An enzyme in the ER of the liver - Takes glucose-6-phosphate and cleaves off the phosphate, creating glucose, which can leave via GLUT transporters - Note: muscle does not have glucose-6-phosphatase, so the glycogen in muscle cannot be a source of blood glucose; thus, muscle supplies only AAs for gluconeogenesis and not glycogen

Answer 118

- Functions: Production of NADPH and serves as a source of ribose-5-phosphate - Glucose-6-phosphate dehydrogenase, which is induced by insulin and NADP+ and inihbited by NADPH

Answer 119

- Cells require NADPH for a variety of functions, including: 1. Biosynthesis, mainly of fatty acids and cholesterol 2. Assisting inc ellular bleach production in certain white blood cells, thereby contribuitng to bactericidal activity 3. Maintenance of a supply of reduced glutathione to protect against reactive oxygen species (acting as the body's natural antioxidant)

Answer 120

- 2 ATP per molecule of glucose

Answer 121

Takes pyruvate and makes Acetyl-CoA for the citric acid cycle - Located in the mitochondrial matrix

Biochemistry Flashcards

(152 cards)