Lecture 7 Flashcards
What is metabolism?
pertains to all chemical reactions and physical workings of the cell
What is anabolism?
- any process that results in synthesis of cell molecules and structures
- a building and bond-making process that forms larger macromolecules from smaller ones
- requires the input of energy
What is catabolism?
- breaks the bonds of larger molecules into smaller molecules
- releases energy
What are the functions of metabolism?
- assembles smaller molecules into larger macromolecules as needed for the cell; ATP (energy) is utilized to form bonds (anabolism)
- degrades macromolecules into smaller molecules, a process which yields energy (catabolism)
- stores energy in the form of ATP (adenosine triphosphate)
do chemical reactions need enzymes?
yes
What are enzymes?
are catalysts that increase the rate of chemical reactions without becoming part of the products or being consumed in the reaction
How do enzymes work?
Reactants are converted into products by bond formation or bond breakage
What is a substrate?
reactant molecules acted on by an enzyme
What do enzymes do to a reaction?
Speed up the rate of reactions without increasing the temperature
Are enzymes or substrates larger?
enzymes
What is the active site?
Where substrate binds and reacts
lock and key only 1 will work
Process of enzyme
Binds substrate
Participates directly in changes to substrate
Does not become part of the products
Not used up by the reaction
Can be used over and over again
Can enzymes be reused?
Yes
How fast are enzymes?
the number of substrate molecules converted per enzyme per second
catalase: several million
lactate dehydrogenase: a thousand
What do simple enzymes consist of?
just a protein?
What do conjugated enzymes conatin?
protein and nonprotein molecules
What is an apoenzyme?
protein portion of a conjugated enzyme
What is a cofactor?
either organic molecules called coenzymes or inorganic elements (metal ions
What must happen with an enzyme- substrate interaction?
A temporary enzyme-substrate union must occur at the active site
What is the bond between substrate and enzyme like?
Bond formed between the substrate and enzyme are weak and easily reversible
What happens once the enzyme-substrate complex has formed?
an appropriate reaction occurs on the substrate, often with the aid of a cofactor
What is the need of microorganisms for reactions?
The need of microorganisms for trace elements arises from their roles as cofactors for enzymes
What some examples of cofactors?
iron, copper, magnesium, manganese, zinc, cobalt, selenium, etc.
What is the role of cofactors?
- help bring the active site and substrate close together
- participate directly in chemical reactions with the enzyme-substrate complex
What are coenzymes?
organic compounds that work in conjunction with an apoenzyme
What is the general function of a coenzyme?
general function is to remove a chemical group from one substrate molecule and add it to another substrate molecule
-carry and transfer hydrogen atoms, electrons, carbon dioxide, and amino groups
What are coenzymes derived from?
vitamins
How are enzymes classified?
Enzymes are classified and named according to characteristics such as site of action, type of action, and substrate
How is the name of an enzyme derieved?
prefix or stem word derived from a certain characteristic, usually the substrate acted upon or type of reaction catalyzed
ending –ase
What is a carbohydrase?
digests a carbohydrate substrate
What is amylase?
acts on starch
What is maltase?
digests maltose
What are proteinase, protease, and peptidase?
hydrolyzes the peptide bonds of a protein
What is lipase?
digests fats
What is deoxyribnuclease?
digests DNA
What is syntetase or polymerase?
bonds many small molecules together
What are constitutive enzymes?
always present in relatively constant amounts regardless of the amount of substrate
What are regulated enzymes?
production is turned on (induced) or turned off (repressed) in responses to changes in concentration of the substrate
How are enzymes regulated?
Activity of enzymes influenced by the cell’s environment
What are normal conditions for enzymes?
natural temperature, pH, osmotic pressure
changes in the normal conditions causes enzymes to be unstable or labile
How can enzymes be denatured?
weak bonds that maintain the native shape of the apoenzyme are broken
this causes disruption of the enzyme’s shape
prevents the substrate from attaching to the active site
How do metabolic pathways normally occur?
Often occur in a multistep series or pathway, with each step catalyzed by an enzyme
What happens with the product of a reaction?
Product of one reaction is often the reactant (substrate) for the next, forming a linear chain or reaction
What do branches of pathways do?
Many pathways have braches that provide alternate methods for nutrient processing
What is the cylic form of a pathway?
Others have a cyclic form, in which the starting molecule is regenerated to initiate another turn of the cycle
Do metabolic pathways stand alone or together/
Do not stand alone; interconnected and merge at many sites
What is competitive inhibition?
Molecule that mimcks substrate occupies the active site, preventing the actual substrate from binding
What is noncompetitive inhibition?
enzymes have two binding sites: the active site and a regulatory site
molecules bind to the regulatory site
slows down enzymatic activity once a certain concentration of product is reached
What is enzyme repression?
genetic apparatus responsible for replacing enzymes is repressed
(takes longer than feedback inhibition)
What is enzyme induction?
enzymes appear (are induced) only when suitable substrates are present
What happens when E. coli is inoculated into a medium containing only lactose?
it will produce the enzyme lactase to hydrolyze it into glucose and galactose
What happens If E. coli is subsequently inoculated into a medium containing only sucrose?
it will cease to synthesizing lactase and begin synthesizing sucrase
What does enzyme induction in e. coli allow the organism to do?
Allows the organism to utilize a variety of nutrients, and prevents it from wasting energy by making enzymes for which no substrates are present
What is exergonic ?
reactions release energy, making it available for cellular work
What is endergonic?
reactions are driven forward with the addition of energy
What are exergonic and endergonic done together or separate?
Exergonic and endergonic reactions are often coupled so that released energy is immediately put to work
What happens during exergonic reactions?
During exergonic reactions, energy released by bonds is stored in high-energy phosphate bonds such as ATP
What fuels endergonic cell reactions?
ATP fuels endergonic cell reactions
What is oxidation?
loss of electrons
when a compound loses electrons, it is oxidized
What is reduction?
gain of electrons
when a compound gains electrons, it is reduced
What are oxidation-redution reactions?
Oxidation-reduction (redox) reactions are common in the cell and are indispensable to the required energy transformations
What are oxidoreductases?
enzymes that remove electrons from one substrate and add them to another
What are the coenzymes in oxidoredutases?
their coenzyme carriers are nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD)
What is a redox pair?
an electron donor and an electron acceptor involved in a redox reaction
What can happen to energy present in the electron acceptor?
Energy present in the electron acceptor can be captured to phosphorylate (add an inorganic phosphate) to ADP or to some other compound to store energy in ATP
What does metabolism do in catabolism?
Metabolism uses enzymes to catabolize organic molecules to precursor molecules that cells then use to anabolize larger, more complex molecules
What is reducing power?
electrons available in NADH and FADH2
Where is energy stored?
stored in the bonds of ATP
What is aerobic respiration?
a series of reactions that converts glucose to CO2 and allows the cell to recover significant amounts of energy
What is utilized in aerobic respiration?
utilizes glycolysis, the Krebs cycle, and the electron transport chain
What does aerobic respiration rely on?
relies on free oxygen as the final electron and hydrogen acceptor
Who performs aerobic respiration?
characteristic of many bacteria, fungi, protozoa, and animals
What is anaerobic respiration?
used by strictly anaerobic organisms and those who are able to metabolize with or without oxygen
What is involved with anaerobic respirtation?
involves glycolysis, the Krebs cycle, and the electron transport chain
What are used as final electron acceptors in anaerobic respiration?
uses NO3-, SO42-, CO33-, and other oxidized compounds as final electron acceptors
What is fermentation?
incomplete oxidation of glucose
Is oxygen required in fermentation?
no
What are the final electron acceptors in fermentation?
organic compounds
Where does the kreb cyle take place?
The Krebs cycle takes place in the cytoplasm of bacteria and in the mitochondrial matrix of eukaryotes
What is the electron transport chain?
A chain of special redox carriers that receives reduced carriers (NADH, FADH2) generated by glycolysis and the Krebs cycle
Where does the electron transport chain occur in prokaryotes?
the cell membrane
Where does the electron transport chain occur in eukaryotes?
inner mitochondrial membrane
Where does released energy from electron carries go?
Released energy from electron carriers in the electron transport chain is channeled through ATP synthase
What happens in the final step of the electron transport chain?
in the final step of the process, oxygen accepts electrons and hydrogen, forming water
What is oxidative phosporylation?
the coupling of ATP synthesis to electron transport
How many atps does Nadh give rise to in the electron chain?
3
how many atps does fadh2 give rise to in the electron chain?
2
what happens in the terminal step of aerobic respiration?
catalyzed by cytochrome aa3, also known as cytochrome oxidase
adapted to receive electrons from cytochrome c, pick up hydrogens from solution, and react with oxygen to form water
2H+ + 2e- + ½ O2 H20
