CHAPTER 6 Flashcards
PHOTOSYNTHESIS
*light energy is used to rearrange atoms of CO2 (carbon dioxide) and H2O (water) to produce organic molecules (sugars) and O2 (oxygen)
CELLULAR RESPIRATION
*O2 (oxygen) is consumed as organic molecules are broken down to CO2 (carbon dioxide) and H2O (water) and the cell captures energy as ATP
BREATHING & CELLULAR RESPIRATION
- Breathing supplies O2 (oxygen) to cells and removes CO2 (carbon dioxide)
- Breathing and cellular respiration closely related:
- *Breathing brings O2 (oxygen) into the body from the environment, distributed via bloodstream
- *Cellular respiration, mitochondria, use O2 (oxygen) to harvest energy and generate ATP
- *Breathing disposes of the CO2 (carbon dioxide) produced as a waste product of cellular respiration
CELLULAR RESPIRATION
Cellular respiration stores energy in ATP molecules
**Reactants O2 (oxygen) and C6H12O6 (glucose) re-group to form products CO2 (carbon dioxide) and H2O (water)
**Energy from C6H12O6 (glucose) is released and stored as ATP
**C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O + ATP
glucose. oxygen. carbon. water. energy
dioxide
REDOX REACTIONS
- During cellular respiration, electrons are transferred from C6H12O6 (glucose) to O2 (oxygen), releasing energy
- Transfer of electrons from one molecule to another is a redox reaction
- In a redox reaction:
- *Loss of electrons is oxidation
- *Gain of electrons is reduction
REDOX REACTIONS OF CELLULAR RESPIRATION
*Glucose loses electrons (in H atoms) and becomes oxidized
*O2 gains electrons (in H atoms) and becomes reduced
*Electrons lose potential energy and energy is released
C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O + ATP
(C6H12O6 and 6 CO2 = OXIDATION)
(6 O2 and 6 H2O = REDUCTION)
REDOX REACTIONS
- Redox reactions that break down glucose involve an enzyme and a coenzyme
- Enzyme dehydrogenase removes electrons (in H atoms) from fuel molecules (oxidation)
- Electrons are transferred to the coenzyme NAD+ which is reduced to NADH
NAD+ 2H –REDUCTION–»> NADH + H+
STAGES OF CELLULAR RESPIRATION
*Cellular respiration occurs in 3 stages
GLYCOLYSIS (STAGE 1)
- Glycolysis occurs in the cytoplasm
* Glycolysis breaks down Glucose to Pyruvate producing small amounts of ATP
CITRIC ACID (STAGE 2)
- Citric acid occurs in the mitochondria
- Completes breakdown of glucose producing CO2 and small amount of ATP
- Supplies electrons for third stage
OXIDATIVE PHOSPHORYLATION (STAGE 3)
- Occurs in mitochondria
- Uses energy released by electrons down electron transport chain to pump H+ across a membrane
- Harness energy of H+ gradient through chemiosmosis producing ATP
GLYCOLYSIS
- Harvests chemical energy by oxidizing glucose to pyruvate
- Glycolysis splits sugar molecules in the cytoplasm
- *Starts with a single 6 Carbon molecule of pyruvate
- *Ends with a double 3 carbon molecule of pyruvate
- *Produces two molecules of ATP
GLYCOLYSIS
- Produces ATP by substrate-level phosphorylation
- *An enzyme transfers a phosphate group from an organic molecule to ADP
- *Small amount of ATP produced
PYRUVATE OXIDATION
- Pyruvate used for citric acid cycle
- A large, multi-enzyme complex catalyzes 3 reactions in the mitochondrial mix
- *Carbon atom is removed from pyruvate and released in CO2
- *Remaining two-carbon compound is oxidized, and a molecule of NAD+ is reduced to NADH
- *Coenzyme A joins with the 2-carbon group to produce Acetyl CoA
CITRIC ACID CYCLE
- Citric acid cycle generates many NADH and FADH2 molecules
- For each turn of the citric acid cycle:
- *2 CO2 molecules are released
- *Energy yield is 1ATP, 3NADH, and 1FADH2
ATP
- Most ATP production occurs by oxidative phosphorylation
- An electron transport chain in mitochondrial membrane creates an H+ gradient
- Electrons from NADH and FADH2 travel down the chain to O2 which picks up H+
- H2O is product
- Energy released by redox reactions actively transport H+ across the membrane from the mitochondrial matrix to the inter membrane space
CHEMIOSMOSIS
- ATP synthases drives synthesis of ATP
- Exergonic reactions of electron transport chain produce H+ gradient that stores potential energy
- ATP synthases harness the energy by acting like turbines
- Help H+ diffuse back against the gradient through the inner membrane
- Attach phosphate groups to ADP producing ATP
REVIEW
- Each molecule of glucose yields many molecules of ATP
- Glycolysis and citric acid cycle together yield 4 ATP per glucose molecule
- Oxidative phosphorylation, using electron transport and chemiosmosis yields 34 ATP per glucose
- These numbers are maximums
- *Some cells may lose a few ATP to NAD+ or FAD shuttles
FERMENATION
- A way of harvesting energy that doesn’t require oxygen
- Pathway that generates ATP during fermentation is glycolysis
- Glycolysis uses NO oxygen - it is anaerobic
- **Glycolysis anaerobic
- Glycolysis generates 2ATP and 2 pyruvate molecules and REDUCES NAD+ to NADH
FERMENATION
- Fermenation is an anaerobic alternative to cellular respiration
- **Fermenation anaerobic
- Fermenation:
- *Generates ATP molecules from glycolysis in the absence of oxygen
- *Recycles NADH to NAD+ anaerobically
- Muscle cells use lactic acid fermentation
- *NADH is OXIDIZED to NAD+ as pyruvate is REDUCED to lactate
ANAEROBES
- Obligate Anaerobes:
- *Require anaerobic conditions to generate ATP by fermenation
- *Poisoned by oxygen
- Facultative Anaerobes:
- *Can make ATP by fermentation or oxidative phosphorylation depending on whether O2 is available
FOOD MOLECULE AND CELLS
*Cells use many kinds of organic molecules as fuel for cellular respiration
*Cells use 3 main kinds of food molecules to make ATP
1 Carbohydrates: hydrolyzed by enzymes to glucose which enters glycolysis
2 Proteins: digested to constituent amino acids, become intermediates in glycolysis or the citric acid cycle
3 Fats: digested to glycerol and free fatty acids, fatty acids are broken-down and enter the citric acid cycle as acetyl CoA
FOOD MOLECULES
- Food molecules provide raw materials for biosynthesis
- Some raw materials from food can be incorporated directly into an organisms molecules
- Cells can also make molecules not found in food
- Biosynthetic pathways consume ATP rather than produce it
RESPIRATION
- Fuel for respiration ultimately comes from photosynthesis
- All organisms can harvest energy from organic molecules
- Plants can also make molecules from inorganic sources by photosynthesis
