Biochemistry Flashcards
_______________
- fundamental subunit of polypeptides/proteins
Amino acid
(AA)
There are ____ amino acids that are coded for by the DNA & there are ____ essential amino acids and ____ nonessential amino acids
20
9
11
Amino Acid Structure includes :
____________ bonded to a hydrogen
____________ group
____________ group
____________ group
Central a-carbon bonded to a hydrogen
Amine group (-NH2)
Carboxyl group (-COOH)
Variable functional group (R-group)
All amino acids are chiral except ____________
Glycine
_______________
- 4 different distinct groups bound to an α-Carbon resulting in non-superimposable mirror-images
- a form of isomer with different configuration around a chiral center (forms 2 isomers)
Enantiomers
Amino acids form __________ at low pH
Amino acids form __________ at high pH
Amino acids form __________ at intermediate pH
Cations
Anions
Neutral zwitterions (contains both positive and negative electrical charges, but the net charge on the molecule is zero COO- & NH3+)
R-group chemical properties :
____________ - aliphatic or aromatic
____________ - pH neutral, acidic, alkaline, 3 with sulfur, or selenium
Non-polar
Polar
____________
- amino acids form peptide bonds by dehydration synthesis between the amino group of 1 amino acid & the carboxyl group of another amino acid
Polypeptide synthesis
Polypeptide synthesis is facilitated by ribosomes during ____________ of mRNA
translation
Proteins are composed of 1 or more long ____________ molecules
polypeptide
Other bonds formed in the synthesis & activation of proteins include __________ linkages between cysteine R-groups and __________ bonds between polar R-groups
Disulfide linkages
Hydrogen Bonds
In protein digestion, the protease or peptidase enzymes break peptide bonds via ____________
Hydrolysis
____________ structure
- actual sequence of amino acids in the protein due to peptide bonds
Primary structure
____________ structure
- 2 common configurations
- a-helix & B-pleated sheet are due to Hydrogen bonds between amine hydrogens and carbonyl oxygen of amino acids
- especially prevalent in fibrous structural proteins
Secondary structure
____________ structure
- 3D shape of entire polypeptide due to interaction among hydrophobic R-groups & hydrophilic R-groups, hydrogen bonds, ionic bonds, & disulfide bridges between cysteine R-groups
Tertiary structure
Structural proteins usually have ________ tertiary structures
Fibrous
Enzymes usually have ________ tertiary structures
Globular
____________ structures
- 2 or more polypeptides combine to form a functional protein or incorporation of ligands
- ex : Fe containing heme groups of hemoglobin
Quaternary structures
Long sequences of (non-polar OR polar) amino acids are found in membrane-bound proteins or membrane-embedded proteins & attach protein to lipid bilayer or folded into the interior to stabilize the 3D structure of proteins dissolved in water
Non-polar
____________
- disruption of protein/polypeptide folding & activity by changes in pH, Temperature, or presence of hydrophobic solvents
Denaturation
____________
- correct refolding of denatured protein
Renaturation
____________
- dissolved proteins are surrounded by water molecules oriented according to the charges of the amino acids in that particular surface of the folded protein
- have properties key to binding of substrates to protein active sites
Solvation layer
____________
- proteins are forced by electric current to pass through a medium that sorts molecules by size, charge, and/or other chemical properties
Electrophoresis
__________________
- proteins have unique combinations of R-groups charged positive or negative
- at a specific pH then a particular protein acquires neutral charge (therefore stops moving due to no electromagnetic field force)
- proteins then separated along a pH gradient gel with cathode & anode charges at either end
Isoelectric focusing
____________ chromatography
- mixtures of proteins dissolved in a solvent pass by gravity or under pressure through a medium that binds with varied affinity to substances in the mixture
- more soluble (lower binding affinity) molecules pass through the column fastest & others lag behind so each can be collected as it passes through the column
Column chromatography
_________________
- different molecules’ mass-to-charge ratios detected by bombarding them with beams of electrons
- magnetic field separates charged molecules by mass & charge
Mass spectrometry
X-ray crystallography & computer modeling can help determine _______________
3D protein folding
True or False
Protein function is due to conformational strength, stability, & binding specificity
True
Functions of ___________
- enzymes, providing structure, facilitating movement, transport, or storage of substances & communication
- membrane bound, dissolved, or suspended in organelles or cytosol or are secreted out of cells
proteins
____________ proteins
- collagen (cartilage, bone, tendon)
- keratin (nails, hair, horn)
- histones (DNA supercoiling)
- cytoskeleton
- bacterial/fungal cell walls
Structural
____________
- catalysts of biochemical reactions
- suffix : -ase
Enzymes
Proteins that help facilitate ____________
- muscle function (actin, myosin, tropomyosin)
- kinesins
- flagella
- cilia
Movement
__________ & _________ proteins
- membrane pumps
- membrane channels
- hemoglobin
- myoglobin
Transport & Storage proteins
___________ & __________ proteins
- peptide hormones (insulin, adrenalin)
- neurotransmitters
- antigens (surface markers)
- antibodies (target non-self antigens)
Communication & Identification proteins
____________
- proteins that catalyze biochemical reactions
- production, activation, & regulation determine the complex biochemical dynamics in living organisms
- not reactants & can catalyze the same reaction repeatedly
- highly substrate specific & enzymes specificity includes stereochemistry
- do not influence the thermodynamics (just kinetic reaction rate)
Enzymes
Energy consumed in ____________ enzyme catalyzed reactions are usually obtained when the enzyme activity is coupled with the __________ catalysis of the reaction ATP –> ADP + Pi
endergonic
exergonic
Enzyme-catalyzed reactions are linked sequentially to form ________________
Biochemical pathways
____________
- series of gradual chemical changes in a reactant to form a particular product
Biochemical pathways
____________
- biochemical reactions/pathways break down complex molecules into simpler molecules or release potential chemical energy stored in chemical bonds
- associated with digestion, hydrolysis, oxidation, & exergonic processes
Catabolism
____________
- biochemical reactions/pathways that synthesize complex macromolecules from simpler subunits and/or form bonds that help store chemical energy
- associated with polymerization, dehydration synthesis, reduction, & endergonic processes
Anabolism
____________ reactions
- anabolic reactions & catabolic reactions together
- dephosphorylation of PEP –> pyruvate coupled with substrate-level phosphorylation of ADP to ATP in glycolysis
Coupled reactions
__________ bond with substrates (reactants) at substrate-specific active sites
Enzymes
____________
- change conformation to form enzyme-substrate complex (lowers the activation energy of reactions that create or break substrate bonds by several ways)
Induced fit
The ____________ lowers activation energy of reactions that create or break substrate bonds by :
- conformationally straining bonds so they break more readily
- placing substrates together in an orientation that causes a chemical reaction
- creating an active site microenvironment that induces a reaction
- forming temporary bonds with the substrate as a step toward formation of the product
enzyme-substrate complex
True of false:
Enzymes function within a limited optimal range of temperature & pH conditions
True
Apoenzymes may require cofactors (metal ions or organic molecules) to become activated ____________
Holoenzymes
Cofactors that are permanently incorporated into the enzyme are called _____________
Prosthetic groups
Cofactors that are temporarily bind to enzymes are called ____________
Coenzymes
(ATP, NAD+, coenzyme A)
Enzyme catalysis involves 2 steps:
1.
2.
- Binding of enzyme to substrate to form E-S complex
- formation of product
The ______________________ (aka the Km value) is the substrate concentration
at which the reaction rate
is half of the maximum rate & it is a measure of how well an enzyme binds to its substrate
Michaelis-Menten constant
A (low OR high) Km = high affinity for enzyme to substrate & low rate of catalysis
Low Km
A (low OR high) Km = low enzyme-substrate affinity & high rate of catalysis
High Km
True or false:
The rate of an enzyme reaction or non-enzyme protein binding (antigen/antibody) is a function of substrate concentration [S], Km value, & maximum catalysis rate Vmax
True
True or false:
Temperature & pH affect conformational stability of enzymes (ability to bind or catalyze substrate declines)
True
Enzyme activity is regulated __________ & __________ control of genes coding for those enzymes
transcription
translation
Activation of enzymes by modification of the inactive forms, which are called ____________
zymogens
True or false:
The activation of enzymes occurs by change in the environment (secretion into stomach acid), addition of organic or inorganic covalently bonded groups (phosphorylation), & presence of inhibitors or activators
True
____________ may be products of enzyme catalysis or products farther down the biochemical pathway, or may be substances not directly related to the enzyme-catalyzed reaction
inhibitors
____________ enhance enzyme activity
activators
_______________
- in multi-polypeptide enzymes the substrate binding to 1 subunit enhances binding to others
Positive cooperativity
_______________
- substrate binding to 1 subunit reduces binding to others
Negative cooperativity
______________ inhibition
- inhibitor to substrate that binds to the same active site as the substrate
- formation of enzyme-substrate complex is reduced and therefore Km increases while Vmax stays the same because higher substrate concentration still increases catalysis
Competitive inhibition
______________ inhibition
- inhibitor that binds to the enzyme but not at the active site (allosteric change to enzyme conformation)
- prevents enzyme-substrate complex from completing catalysis
- enzyme still binds to substrate so Km stays the same but Vmax decreases
Non-competitive inhibition
______________ inhibition
- inhibitor binds to enzyme-substrate complex and prevents enzyme-substrate binding & prevents catalysis
- Km increases and Vmax decreases
Uncompetitive inhibition
The inverse of the _______________ rate yields a linear equation that when graphed it clarifies the effects of enzyme inhibitors on Km or Vmax
Michaelis-Menten
______________
- subunit of nucleic acids
- contains a phosphate, a 5-Carbon Sugar, & a Nitrogenous base (A, G, C, T, or U)
Nucleotide
________ : nitrogenous bases bound to ribose
________ : nitrogenous bases bound to deoxyribose
RNA
DNA
The DNA molecule forms a double helix (twisted ladder structure) :
“Rails” are alternating __________ & __________
“Rungs” are the __________
deoxyribose & phosphate subunits
base pairs
Bonds between the base pairs in DNA molecules are ___________
H bonds
Bonds between alternating deoxyribose & phosphate subunits in DNA molecules are ____________
Phosphodiester bonds
In DNA the phosphodiester linkage is highly stable and the helical structure is maintained by ____________ between nonadjacent sugar molecules as the molecule twists
H bonds
Base pairing : between a purine & a pyrimidine
A pairs to _____
C pairs to _____
A to T
C to G
The base pairing between A & T contains a ________ H bond
The base pairing between C & G contains a ________ H bond
Double
Triple
______________ rule
- equal concentrations of A & T also same for C & G
Chargaff’s rule
DNA strands are ____________
- sequence of 1 strand can be known from the other strand
complementary
DNA strands are ____________
- the 5’ carbon of the sugar molecules & phosphate on 1 strand are in opposite directions on the other complementary strand
- the 3’ carbons of each sugar are opposite the 5’ ends
- because of the orientation of the 2 strands, 1 end of each strand is designated the 5’ end & the other is the 3’ end
antiparallel
True or False :
In DNA molecules there are thousands to several hundred million base pairs and the hydrogen bonds are weak but the cumulative effect makes the double strand stable
True
The denaturation of DNA molecules can be caused by Heat, Acid, or Enzymes can disrupt the __________ holding the strands together
H bonds
DNA _______ denaturation is the first step in a variety of techniques including DNA hybridization & PCR
Heat
In DNA heat denaturation the more A-T pairs there are then the (lower OR higher) the temperature required to cause denaturation
Lower
- due to A-T only having 2 H bonds than compared to C-G having 3 H bonds
DNA ____________
- cooling process after heat denaturation so the DNA strands restore base pairing
Annealing
DNA ____________
- denatured DNA from different sources are combined and allowed to reanneal (similar sequences bind together)
- used to help locate or mark specific sequences or genes or measure similarity of 2 DNA molecules
DNA Hybridization
In RNA, the pyrimidine __________ replaces Thymine as the base complementary to Adenine
Uracil
True or False :
RNA molecules are much smaller and more mobile than to their parent DNA molecules in chromosome
True
DNA has 2 functions :
____________
____________
Heredity
Genes
______________
- responsible for carrying traits from 1 generation to the next generation
Heredity
______________
- information to make protein and RNA
Genes
______________ RNA
- is a transcribed gene
- prokaryotes : contains all the info to synthesize a single polypeptide
- eukaryotes : primary transcript introns are spliced out to form secondary transcript
mRNA
- messenger RNA
______________ RNA
- most transfer RNA molecules carry 1 of the 20 amino acids to ribosomes which are creating a polypeptide
- contains a 3-base anticodon which pairs with a mRNA codon
tRNA
- transfer RNA
______________
- a component of ribosomes in which catalyzes peptide bond formation
rRNA
- ribosomal RNA
RNA’s that contribute to __________ regulation
- miRNA, siRNA, snRNA, snoRNA, Xist RNA, CRISPR RNA
Gene regulation
____________ systems are inherently physical & chemical systems
Biological systems
Gibbs free energy incorporates the 2 components of thermodynamics in chemical systems
____________ & ____________
Enthalpy (H) & Entropy (S)
In Gibbs free energy, if the G > 0 then the process is ______________
Endergonic (consumes energy)
In Gibbs free energy, if the G < 0 then the process is _____________
Exergonic (releases energy)
____________
- biological systems convert light energy into chemical energy
Photosynthesis
______________
- biological systems convert chemical energy into other forms of chemical energy
Cellular respiration
____________ affect the rate at which biochemical reactions reach equilibrium but do not affect the final equilibrium concentrations
Catalysts
Increasing concentration of either of the __________ increases the forward reaction until equilibrium concentrations are reestablished
reactants
Increasing concentration of either of the __________ increases the reverse reaction until equilibrium is reestablished
products
______________
- the ribonucleoside Adenosine bound to a trimer of 3 phosphates linked by high-energy phosphodiester bonds
ATP
ATP & GTP act as __________ in many endergonic enzyme-catalyzed reactions so when the enzyme, motor protein, or membrane pump binds to its substrate then it also binds to an ATP at a different site
coenzyme
In the ATP molecule, hydrolysis of the phosphodiester bond between the 2nd and 3rd phosphates cause a release of ______ Kcal/mol.
7.3 Kcal/mol.
Enzyme : ____________
- remove a -COOH group
Carboxylases
Enzyme : _______/__________
- catalyze oxidation reactions
- use electron carriers (NAD+ & FAD) and other flavonoids as cofactors
- some reactions also decarboxylate the substrate
Oxidase / dehydrogenases
Enzyme : ____________
- transfer phosphate groups to substrates
Kinases
Enzyme : ____________
- remove a phosphate
Phosphatases
Enzyme : ____________
- reconfigure the molecule to an isomer
Isomerases
Enzyme : ____________
- add an electron (accompanied by an H+ from NADH + H+ or from FADH2)
Reductases
Enzyme : ________/_________
- responsible for anabolic formation of macromolecules
Polymerases / Synthases
Digestive / Catabolic enzymes are named for the substrate they break down :
________ - break down protein
________ - break down lipids
________ - break down lactose
________ - break down maltose
________ - break down nucleic acids
Proteases
Lipases
Lactase
Maltase
Nucleases
____________
- the 1st step in cellular respiration
- oxidizes food molecules (glucose) and uses energy released to catalyze ADP + Pi –> ATP
- occurs in cytoplasm of all cells
Glycolysis
Glycolysis summary :
- the 1st 3 reactions consume _____ ATP molecules to convert glucose to fructose biphosphate (the negatively charged phosphates help split the Hexose to form _____ 3-Carbon glyceraldehyde phosphates
- in a series of oxidative reactions, _____ G3P are converted to 2 pyruvate and these steps produce 4 ATP as well as 2 molecules of reduced electron carrier NADH + H+
2
2
Glycolytic intermediates are precursors for many __________ processes
anabolic
____________
- anaerobically recycles NAD+ to glycolysis
Fermentation
____________ fermentation
- anaerobic bacteria & yeast
- 2 pyruvate –> 2 ethanol + 2 CO2
- coupled with NADH + H+ –> NAD+
Ethanol fermentation
____________ fermentation
- muscle cells that are O2 stressed (anaerobic)
- 2 pyruvate –> 2 lactate
- coupled with NADH + H+ –> NAD+
Lactic acid fermentation
____________
- synthesizes glucose from simpler molecules including lactate, glycerol, glutamine, & alanine
- these molecules converted to pyruvate which is then reduced to form glucose
- “essentially reverse glycolysis”
Gluconeogenesis
Gluconeogenesis derives its energy by consuming _____ ATP molecules and _____ GTP molecules
4 ATP
2 GTP
Gluconeogensis occurs mainly in ________ cells and is regulated by production of glucagon in the pancreas when blood sugar is too low
Liver cells
____________
- an alternative pathway in which energy from glucose is used to synthesize NADPH (a reduced electron carrier/coenzyme in many anabolic processes
- also used as an antioxidant to reduce cell damage by free radicals
- pathway yields ribose (nucleotide synthesis) & erythrose (aromatic amino acid synthesis)
Pentose Phosphate Pathway (PPP)
The Pentose Phosphate Pathway takes place predominantly in the __________
Liver
Aerobic Respiration : 4 steps
1.
2.
3.
4.
Glycolysis
Pyruvate Oxidation
Citric Acid Cycle
Oxidative Phosphorylation (ETC)
Acetyl-CoA is transported into the _______________
Mitochondrial Matrix
All 6 carbons from glucose during aerobic respiration are converted to __________
CO2
True or False :
Intermediate substrates of Citric Acid cycle are involved in other pathways
True
____________
- final pathway in aerobic respiration
- yields additional 26-28 ATP per glucose
- NADH + H+ & FADH2 in the mitochondrial matrix give their electrons to a series of protein complexes in the inner mitochondrial membrane
- as electrons pass between the protein complexes the H+ are pumped from matrix to intermembrane space
Electron transport chain (ETC)
In Electron Transport Chain, the accumulation of protons (H+) is called _______________
Chemiosmotic Potential
True or False:
Protons (H+) pass through ATP synthase complexes embedded in inner membrane, the positive charge helps neutralize repulsion between phosphates, allows new phosphodiester bonds to form, & the protons (H+) passing through ATP synthase and the electrons from the ETC react with O2 to form H2O
True
Anaerobic respiration net yield of ATP is _____
Aerobic respiration net yield of ATP is _____
2 ATP
30-32 ATP
Carbohydrate homeostasis combines __________ enzyme control of respiratory pathways with hormonal regulation
Allosteric
In glycolysis, enzymes that phosphorylate or dephosphorylate substrates act as sites of control :
- high concentration of ______ inhibits phosphofructokinase which stops the production of fructose diphosphate
ATP
Reactions in the Citric Acid Cycle are :
- inhibited by high concentrations of ____________ & ________
- stimulated by high concentrations of _________
NADH + H+ & ATP
ADP
High or Low glucose stimulates either production or oxidation of __________
Lipids
High glucose –> production of lipids
Low glucose –> oxidation of lipids
The hormone ____________ causes glycogen formation, gluconeogenesis, and production of gastrin & CCK
Glucagon
__________ hormones control basal metabolic rates
Thyroid
____________
- damage to biomolecules/cells/tissues due to reactivity of oxygen-free radicals & peroxides
- reactive oxidizers are necessary to the electron transport chain, immune system function, and cell-signaling mechanisms
- overabundance of reactive oxidizers can trigger cell apoptosis or necrosis at the tissue level
- degenerative, developmental, cardiovascular diseases, & cancer are associated
Oxidative stress
Apoptosis
- enzyme-controlled cell death that is mediated in part by mitochondrial exposure to oxidative stress then the mitochondria release cytochrome C and several enzyme activators that stimulate activity of ____________ enzymes (trigger the cascade leading to apoptosis
Caspase enzymes
__________ factors that affect metabolism & body mass regulation
- diet (caloric intake & food type), physical activity, sleep patterns, pollutants/toxins, medications, & cultural/economic factors
Environmental factors
__________ factors that affect metabolism & body mass regulation
- levels of thyroid hormones, liver function, & specific genetic conditions
Genetic factors
Gut flora, pathogens, & parasites can influence body mass and __________ uptake
Nutrient
High body mass creates a positive feedback and hormones that enhance appetite (leptin & CCK) are produced by __________ tissue
Adipose (fat)
__________
- pathological syndrome associated with increased affluence in developing countries & poverty in developed countries
Obesity
__________ synthesis
- if ATP demand is low & glucose levels are high then acety-CoA diverts from respiration to FA synthesis
- fatty acid synthases form a growing hydrocarbon chain using NADPH as a reducing agent
- primarily in liver, adipose, & mammary tissue
Fatty acid synthesis
The energy yield from fat oxidation is ______ kcal/g compared to the energy yield from carbohydrates or proteins of 4 kcal/g
9 kcal/g
Ingested or stored fats are digested by __________
Lipases
Fatty acids are transported bound to ____________
albumin
Inside mitochondria, fatty acids undergo ____________ which cleaves off 2 carbons at a time from the fatty acid and forming acetyl-CoA which enters the Krebs cycle
Beta-Oxidation
__________ bodies
- are 3 biochemicals when food is not available or energy demands exceeds carbohydrate supply
- 2 can become acetyl-CoA but the 3rd (acetone) is excreted but can reach toxic levels (leading to ketoacidosis)
Ketone bodies
__________
- breakdown of proteins into its component amino acids
Proteolysis
__________ synthesis is accomplished by ribosomes
Protein synthesis
The digestive system has __________ enzymes that catabolize proteins so amino acids can be absorbed and then transported to cells to be used in gene expression/protein synthesis
protease enzymes
Low carb & low fat causes dietary or cellular __________ to be used as energy sources (broken down in the liver by transamination to alpha-keto acids & converted to acetyl-CoA for oxidation in the Krebs cycle)
proteins
__________
- causes glycogen to be broken down into glucose to be used as an energy source
- causes fat catabolism to ketone bodies to provide energy to the brain
- causes protein to be catalyzed
Starvation
__________
- a diverse group of hydrophobic biochemicals with a wide range of functions
- fats, oils (acylglycerols) waxes, steroids, & terpenes
Lipids
__________ functions
- long-term energy storage, cell membranes (phosphodiglycerides & cholesterol), thermal & electrical insulation, waterproofing (waxes), buoyancy, padding, hormones (steroids), plant defenses (terpenes), and communication (pheromones)
lipid functions
Fats & oils are a glycerol with ________ bonds to 1-3 fatty acids (termed -glycerides)
ester bonds
__________
- a carboxyl group & a long hydrocarbon polymer
Fatty acids
__________ fatty acids
- single bonds between pair of carbons
Saturated fatty acids
__________ fatty acids
- 1 or more double bonds between carbons in the hydrocarbon chain
Unsaturated fatty acids
True or False:
Fats & oils vary in the number of fatty acids, fatty acid hydrocarbon chain length, & if the fatty acids are saturated or unsaturated
True
Short-chain fatty acids contain _______ carbons
Medium-chain fatty acids contain _______ carbons
Long-chain fatty acids contain _______ or more carbons
4-6
8-12
14-40
Short chain fatty acids are (less OR more) hydrophobic than longer chain fatty acids
Less
__________ unsaturated fatty acids
- contain double bonds between 1 or more carbons
- are straight
trans-unsaturated fatty acids
__________ unsaturated fatty acids
- contain double bonds between 1 or more carbons
- have bends in them that reduce hydrophobicity
cis-unsaturated fatty acids
__________
- synthesized from fatty acids but rearranged to form 4 hydrocarbon rings
Steroids
Carotenoids & Lipophilic vitamins are derived from __________
fatty acids
__________
- phospholipid bilayer
- stable : insoluble in cell’s aqueous environment
- selectively permeable : retains vital ions & biochemicals inside the cell
- fluid : flexible, grow and engulf/discharge substances
- complex mosaic : proteins, sterols, other biochemicals (complex are embedded in, penetrating, or extending from membrane)
Plasma membrane
__________
- contain C, H, & O
- basic formula : (CH2O)n
Carbohydrates
Monosaccharides
________ : 3-C sugars such as glyceraldehydes
________ : 5-C sugars such as ribose & deoxyribose
________ : 6-C sugars such as glucose, fructose, etc.
Trioses
Pentoses
Hexoses
__________
- contain 2 or more monosaccharides connected via dehydration synthesis to form a glycosidic linkage
Disaccharides
__________
- composed of many sugar monomers connected by glycosidic linkages
Polysaccharides
__________
- short term easily transported energy sources
- enter glycolysis as glucose or an intermediate further down the pathway
Monosaccharides
Disaccharides are __________ in the digestive tract before absorption
hydrolyzed
__________
- intermediate length
- often cell surface molecules involved in communication, transport, & recognition
- glycolipids or glycoproteins
Oligosaccharides
__________
- structural (cellulose) or for longer-term energy storage (starches or glycogen)
Polysaccharides
__________ constitutes dietary fiber and is indigestible by animals
Cellulose
__________
- certain genes that when activated & expressed may promote or cause cancer
- may be triggered by mutation, chromosomal translocations, carcinogens, or viruses
- may cause cancer if there is a loss of gene regulation, duplication of the gene, or translocation of the oncogene to a region of higher transcription promotion
- many function by disrupting apoptosis, cause accumulation of a certain type of cell which would normally undergo stable turnover, new cells form to replace old ones that self-destruct via apoptosis
- form proteins that disrupt normal cell differentiation or increase rates of cell proliferation
Oncogenes
True of False:
Many chemotherapy drugs target the oncoprotein products of oncogenes, binding them or allosterically competing with them
True
__________
- complex transmembrane proteins
- when stimulated by membrane voltage potential depolarization or by ligand binding, open & passively facilitate diffusion of a particular ion along a concentration or charge gradient
Gated ion channel
__________
- transmembrane proteins that when activated by binding of an external ligand then catalyze a reaction on the inner membrane surface, often initiating a pathway involved in cell growth or other cell activity
Receptor enzymes
__________
- large complex transmembrane proteins
- receptor component on the cell surface binds to a ligand such as a hormone or neurotransmitter or to a sensory stimulus then a conformational change in the receptor occurs which stimulates a G protein on the interior membrane surface
- uses energy from hydrolysis of GTP where the G protein initiates a cAMP cascade by stimulating adenylate cyclase or comparable pathway to trigger cell specific functions
G protein-coupled receptors
