Chapter 7 Flashcards
mitochondria
- makes ATP, powerhouse of the cell
- has a double membrane, outer an s inner with foldings
- cristae- the folds of the inner membrane
- cellular respiration takes place here
Oxidation and Reduction
- oxidation involves the loss of electrons and reduction involves the gain of electrons
- substrate level-phosphorylation and chemiosmosis
- 2 ways to make ATP
energy intermediates
- ATP- the main energy source, fully charged
- ADP- uncharged
- Pi- inorganic phosphate group
- NADH-fully charged
- NAD+- not charged
- FADH2- fully charged
- FAD- uncharged
Cellular Respiration
- process by which living cells obtain energy from organic molecules
- can use carbohydrates, proteins and fats
- primary aim: to make ATP and NADH
- aerobic respiration uses oxygen
- O2 is consumed and CO2 is released
Cellular Respiration formula
organic molecules + O2 –> CO2 + H2O + Energy
Glucose Metabolism: 4 metabolic pathways
- glycolysis (sugar splitting)
- breakdown of pyruvate
- citric acid cycle
- oxidative phosphorylation
Stage 1: Glycolysis
- can occur with or without oxygen
- steps nearly identical in all living species
- ten steps put in 3 phases
- start with-glucose
- end with 2 pyruvate molecules
- take a 6 C glucose and split it into 2, 3 C molecules
Glycolysis Phase 1: Energy investment
-2 ATP hydrolyzed to create fructose-1,6 bisphosphate
Glycolysis: Phase 1: Cleavage
-6-carbon moelcule broken down into 2, 3-carbon molecules of G3P
Glycolysis: Phase 3: Energy Liberation
- 2 G3P molecules brown down into 2 pyruvate molecules produces 2NADH and 4ATP
Glycolysis net yield
- 2 ATP- energy
- 2NADH- energy (used later)
- 2 pyruvate molecules
Step 2: Breakdown of Pyruvate
- Pyruvate transported to mitochondrial matrix
- broken down by pyruvate dehydrogenase
- moelcule of CO2 is removed
- remaining acetyl group attached to CoA to make acetyl CoA
- 1 NADH made for each pyruvate
Step 3: Citric Acid Cycle
- Metabolic cycle- some molecules enter, others leave
- acetyl is removed from CoA and attached to oxaloacetate to form citrate
- series of steps releases 2CO2, 1ATP, 3NADH and 1FADH2
Stage 4: Oxidative Phosphorylation
- high energy electron removed from NADH and FADH2 to make ATP
- typically requires oxygen
- involves ETC- in inner mitochondrial membrane
- Phosphorylation of ADP to make ATP occurs by ATP synthase
Electron Transport Chain
- group of protein complexes and small organic molecules embedded in inner mitochondrial membrane
- accept or donate electrons in a series of redox reactions
- electron movement generates H+ electrochemical gradient/proton motive force
- excess positive charge outside of matrix
ETC: in detail; NADH
- NADH is oxidized to NAD+
- high energy e- transferred to NADH dehydrogenase to pump H+ into intermembrane space
- e- transferred to ubiquinone
- FADH2 oxidized to FAD: high energy e-‘s transferred to succinate reductase and then to ubiquinone
- e- travels to cytochrome b-c; more H+ pumped out
- e’s transferred to cytochrome c
ETC: in detail; cytochrome oxidase
- e;’s transferred to cytochrome oxidase; more H+ pumped out; e-‘s transferred to oxygen; water is produced
- H+’s flow DOWN their gradient through ATP synthase; this energy is harnessed to make ATP
Phosphorylation: ATP synthase
- lipid bilayer of inner mitochondrial membrane relatively impermeable to H+
- can only pass through ATP synthase
- harnesses free energy release to synthesize ATP from ADP
- chemiosmosis
Chemiosmosis
chemical synthesis of ATP as a result of H+ flowing across a membrane
ATP synthase
- energy conversion-H+ electrochemical gradient or protonmotive force converted to chemical bond energy in ATP
- rotary machine that makes ATP as it spins
- contains several subunits that pump H+ and bind ADP to Pi
NADH oxidation makes most of the cells ATP
- NADH oxidation creates the H+ electrochemical gradient used to synthesize ATP
- yield= up to 30-34 ATP molecules/glucose
- but rarely achieve maximal amount because:
1. NADH also used in anabolic pathways
2. H+ gradient used for other purposes
Carbs, Fat and Protein metabolism
- other molecules besides glucose are used for energy too
- enter into glycolysis or CAC at other points
- using same pathway increases efficiency
- also metabolism used to MAKE molecules
- anabolism
Carbohydrates
0 dont consume all of the carbohydrates in the form of pure glucose
-any carbs you eat get easily converted into glucose then the 4 steps
Protein
- proteins have building blocks of 20 AA
- different amino acids enter the same 4 steps but at different steps along the way
Fats
- super high energy
- most are triglycerides
- broken down into glycerol and separate fatty acids
- glycerol goes into step 2 of glycoylsis and fatty acids get converted into acetyl CoA and from there they proceed right through the same pathway
anabolic metabolism
- metabolism without oxygen
- for environments that lack oxygen or during oxygen deficits
Glucose has two pathways, with oxygen and without
- they both start with glucose and use glycolysis to convert it into pyruvate
- then without oxygen you get lactic acid and ethyl alcohol + CO2
- with oxygen you get the krebs cycle then you get the ETC
Strategy 1: Use other electron acceptors
- E.coli uses nitrate under anaerobic conditions
- NO3- + 2H+ + e- –> NO2- + H2O
- makes ATP via chemiosmosis under aerobic conditions
- ETC is in the plasma membrane
- no mitochondria
Strategy 2: Fermentation
- many organisms can only use O2 as final electron acceptor
- in hypoxic situations, cells can make ATP via glycolysis only
Fermentation: problems
- 2 problems arise with glycolysis-only method of making ATP
1. NADH levels build up - at high concentrations, NADH will haphazardly donate electrons to other molecules forming free radicals
2. NAD+ levels drop - no NAD+ left to be reduced by glycolysis
Fermentation: overcome problems
- muscle cells produce lactate from pyruvate
2. the electrons from NADH are sued to reduce pyruvate ad generate NAD+ –> glycolysis continues
Fermentation: yeast
- yeast break pyruvate into CO2 and acetaldehyde which is then reduced by NADH to ethanol and NAD+
- produces far less ATP (2 vs. 34-38)
Primary metabolism
- synthesis and breakdown of molecules found in all life forms
- essential for cell structure and function *
- lipids, sugars, nucleotides, amino acids and macromolecules
Secondary Metabolism
- synthesis of secondary metabolites that are not necessary for cell structure and growth
- unique to a species or group
- not usually essential for survival *
- commonly made in plants, bacteria and fungi
- roles in defense, attraction, protection and competition
Phenolics
- antioxidants with intense flavors and smells
- neutralize free radicals within cells, helps cells protect there DNA or proteins
Alkaloids
- bitter-tasting molecules for defense
- ex: caffeine, nicotine, codeine
Terpenoids
- intense smells and colors
- ex: rubbery smell, taxol and citronella
Polyketides
- chemical weapons
- bacteria use this
- either to kill them or inflict illness on something
