Metabolism
all chemical and physical workings of a cell
Catabolism
degradative; breaks the bonds of larger molecules forming smaller molecules; releases energy
Anabolism
biosynthesis; process that forms larger macromolecules from smaller molecules; requires energy input
Enzymes are biological catalysts that increase the rate of a chemical reaction by
lowering the energy of activation (the resistance to a reaction)
Conjugated enzymes or holoenzymes
contain protein and non-protein molecules
Apoenzyme
protein portion
Cofactors
non-protein portion
Metallic cofactors
iron, copper, magnesium
Coenzymes
organic molecules: vitamins
Active site, or catalytic site
Site for substrate binding
Induced fit
A temporary enzyme-substrate union occurs when substrate moves into active site
Cofactors act as:
carriers to assist the enzyme in its activity
Micronutrients are needed as:
cofactors
Exoenzymes
transported extracellularly, where they break down large food molecules or harmful chemicals
Cellulase, amylase, penicillinase
Endoenzymes
retained intracellularly and function there
Most enzymes are endoenzymes
Constitutive enzymes
always present, always produced in equal amounts or at equal rates, regardless of the amount of substrate
Regulated enzymes
not constantly present; production is turned on (induced) or turned off (repressed) in response to changes in the substrate concentration
Synthesis or condensation reactions
Anabolic reactions to form covalent bonds between smaller substrate molecules, require ATP, release one molecule of water for each bond formed
Hydrolysis reactions
Catabolic reactions that break down substrates into small molecules; requires the input of water to break bonds
Denaturation
weak bonds that maintain the shape of the apoenzyme are broken
Competitive inhibition
substance that resembles the normal substrate competes with the substrate for the active site
Noncompetitive inhibition
enzymes are regulated by the binding of molecules other than the substrate away from the active site
Enzyme repression
inhibits at the genetic level by controlling synthesis of key enzymes
Enzyme induction
enzymes are made only when suitable substrates are present
Cofactors
A holoenzyme is a combination of a protein and one or more substances called:
Vitamins
Important components of coenzymes are:
Induced Enzymes
Enzymes are produced only when substrate is present are termed:
Energy
the capacity to do work or to cause change
Forms of energy include
Thermal, radiant, electrical, mechanical, atomic, and chemical
Endergonic reactions
consume energy
Exergonic reactions
release energy
Redox reactions
always occur in pairs; There is an electron donor and electron acceptor which constitute a redox pair
Process salvages electrons and their energy
Released energy can be captured to phosphorylate ADP or another compound
Three part molecule consisting of:
Adenine - a nitrogenous base
Ribose - a 5-carbon sugar
3 phosphate groups
Substrate-level phosphorylation
transfer of phosphate group from a phosphorylated compound (substrate) directly to ADP
Substrate-level phosphorylation
transfer of phosphate group from a phosphorylated compound (substrate) directly to ADP
Oxidative phosphorylation
series of redox reactions occurring during respiratory pathway
Photophosphorylation
ATP is formed utilizing the energy of sunlight
Bioenergetics
study of the mechanisms of cellular energy release
Aerobic respiration -
glycolysis, the Kreb's cycle, respiratory chain
Anaerobic respiration -
glycolysis, the Kreb's cycle, respiratory chain; molecular oxygen is not the final electron acceptor
Fermentation
glycolysis, organic compounds are the final electron acceptors
Glycolysis
glucose (6C) is oxidized and split into 2 molecules of pyruvic acid (3C), NADH is generated
TCA
processes pyruvic acid and generates 3 CO2 molecules , NADH and FADH2 are generated
Electron transport chain
accepts electrons from NADH and FADH; generates energy through sequential redox reactions called oxidative phosphorylation
Chain of redox carriers that receive electrons from:
reduced carriers (NADH and FADH2)
ETS shuttles electrons down the chain, energy is released and subsequently captured and used by:
ATP synthase complexes to produce ATP - Oxidative phosphorylation
Chemiosmosis
as the electron transport carriers shuttle electrons, they actively pump hydrogen ions (protons) across the membrane setting up a gradient of hydrogen ions - proton motive force
Light-dependent
photons are absorbed by chlorophyll, carotenoid, and phycobilin pigments
Photosynthesis Occurs in 2 stages:
Light-dependent
Light-independent reaction
Light-independent reaction
dark reactions - Calvin cycle - uses ATP to fix CO2 to ribulose-1,5-bisphosphate and convert it to glucose
Amphibolic
Many pathways of metabolism are bi-directional or
Pyruvic acid
can be converted into amino acids through amination
Deamination
Amino acids can be converted into energy sources through ________
Electron Transport
During which of the phase of cellular respiration, is the majority of ATP formed?
38 ATP
In Bacterial cells, when glucose is completely oxidized by all the pathways of aerobic cellular respiration, how many ATP are generated?
Mitochondria
In eukaryotes, the Krebs cycle takes place in: