CH. 8 - Respiration

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Keywords

1. Overview of Cellular Respiration

1. External Respiration - entrance of air into lungs and gas exchange between alveoli and blood

2. Internal Respiration - includes the exchange of gas between blood and cells

3. Respiration - utilization of oxygen by an organism

2. Glucoise Catabolism

1. Pyruvate - 2 is formed for every glucose burned

2. Glyceraldehyde 3-phosphate (PGAL) - 2 is formed for every glucose burned, precusor to pyruvate

3. Substrate level phosphorylation - producing ATP with enzymes

3. Cellular Respiration

1. Citric Acid Cycle - Kreb Cycle, 6 NADH, 2 FADH2, and 2 ATP formed

2. Cytochrome - electron carriers in the electron transport chain

3. Electron Transport Chain - series of complex carrier mechanisms that makes ATP from ADP.  Total of 32 ATP produced here.

4. Pyruvate Decarboxylation - 2 NADH formed, pyruvate turns into Acetyl CoA

4. Alternative Energy Sources

1. Lipases - enzyme that reduces fat to fatty acids and glycerol

2. Oxidative deamination - ammonia molecules comes directly from the amino acid and is excreted as waste

3. Transamination reaction - process in which amino acid becomes acetyl coA or other intermediate in the citric acid cycle to produce ATP

4. TriCarboxylic Acid Cycle - TCA cycle (also called Kreb cycle), reduces Acetyl CoA

5. Respiration in Invertebrates

1. Spiracle - openings where the tracheae converges and the gas exchange take place

2. Tracheae - used by arthropods, they are tubules where branches reach every cell

6. Respiration in Human

1. Alveoli - gas exchanges take place here via simple diffusion due to partial pressure difference

2. Bronchi - the split from the trachea

3. Bronchioles - splits from the bronchi

4. Epiglottis - the next location after the throat (analogous to esophagus)

5. Larynx - voice box

6. Nare - the nose

7. Pharynx - the throat

8. Trachea - the main lung tube, splits into two

Overview of Cellular Respiration

1. General

1. Photosynthesis - coverts energy of sun into chemical energy of glucose

2. Respiration - conversion of chemical energy in glucose into the usable energy needed to drive the process of living cells

3. Favored Fuel in Body

1. Carbohydrates and fats

1. When hydrogen is removed, energy is made available

2. C-H is capable of releasing the largest amount of energy per mole

4. Carbon dioxide contains little usable energy and is the stable, "energy exhausted" end product of respiration

5. Steps to harnessing energy of hydrogen

1. Dehydrogenation - breaks the hydrogen bond in an oxidation reaction step

1. Energy released is stored in high energy phosphate bond in ATP

2. Done in electron transport chain to fully harness the energy of the redox reaction

Glucose Catabolism

1. Glycolysis

1. General

1. Series of reactions that leads to oxidative breakdown of glucose into

1. 2x Pyruvate

2. 2x ATP

3. 2x NADH

2. Occurs in the cytoplasm with help of enzymes

2. Glycolytic Pathway

1. One molecule of glucose is changed into fructose 1,6 diphosphate

2. Fructose 1,6 diphosphate is broken down into

1. Dihydroxyacetone phosphate

1. This is later isomerized into PGAL as well

2. Glyceraldehyde 3-phosphate (PGAL)

3. Glyceraldehyde 3-phosphate eventually turns into pyruvate

1. 2 is obtained for every glucose

2. 2 ATP is used, but 4 ATP are generated, netting +2 ATP

1. Substrate Level phosphorylation - ATP synthesis by enzyme, not with electron transport chain

3. 2 NADH is obtained for every glucose as PGAL turns into pyruvate

4. In anaerobic conditions, the pyruvate will be reduced via fermentation

5. In aerobic conditions, the pyruvate will be further oxidized in mitochondria

3. Fermentation

1. General

1. NAD+ must be regenerated for glycolysis to continue in absence of O2, so by reducing pyruvate, NAD+ is regenerated.

2. Fermentation only produces 2 ATP per glucose molecule

2. Alcohol fermentation

1. Occurs in yeasts and bacteria

2. Pyruvate produced in glycolysis is converted to ethanol

3. Lactic Acid Fermentation

1. Occurs in fungi, bacteria, and human muscle cells during heavy exercise

2. Pyruvate produced is converted to lactic acid to regenerate NAD+

2. Cellular Respiration

1. General

1. Most efficient catabolic pathway used by organisms to gain back energy stored in glucose

2. Glycolysis yields only 2 ATP, cellular respiration can yield 36~38 ATP.

1. Requires oxygen since it's the final electron acceptor

2. Catalyzed by many enzymes

3. Cellular Respiration can be split into 3 stages - pyruvate decarboxylation, citric acid cycle, and electron transport chain

2. Pyruvate decarboxylation

1. The pyruvate formed during glycolysis is transported into the mitochondrial matrix and here, it is decarboxylated (loses CO2 and coenzyme A attaches)

2. NAD+ is reduced to NADH here

3. Net result is +2 NADH

3. Citric Acid Cycle

1. Also known as the Krebs cycle.

2. Begins when acetyl CoA (once pyruvate) combines with oxaloacetate

1. Forms 6-carbon citrate

3. After a series of reactions, 2 CO2 are released and oxaloacetate is regenerated

4. Each turn of the citric acid cycle produces

1. 1 ATP

2. 1 FADH2

3. 3 NADH

4. 2 CO2

5. Consumes 4 H2O

4. Electron Transport Chain

1. Complex carrier mechanism located inside the inner mitochondrial membrane

2. With ATP synthase, high energy potential electrons are transferred from NADH and FADH2 to oxygen via carriers called cytochromes

3. The central functional unit is an iron atom that can be reduced and oxidized

4. Sequential redox reactions occur as electrons are transferred from one cytochrome to the next.  With each reduction and oxidation, an ADP becomes ATP

5. The final electron acceptor is oxygen.

3. Total Energy Production

1. Substrate Level Phosphorylation

1. Degradation of glucose yields 2 ATP from glycolysis

2. Kreb cycle yields 1 ATP for each turn

3. Total of 4 ATP produced

2. Oxidative Phosphorylation

1. 2 pyruvate decarboxylation yields 2 NADH

2. Each turn of Kreb cycle yields 3 NADH and 1 FADH2

3. Each NADH generates 3 ATP

4. Each FADH2 generates 2 ATP

5. Total of 32 ATP produced

3. Prokaryotes

1. 38 ATP yielded

4. Eukaryotes

1. 36 ATP yielded (2 NADH from glycolysis has to go inside the membrane, thus loses 2 potential ATP)

Alternative Energy Sources

1. General

1. Energy source preference order

1. Other carbohydrates

2. Fats

3. Protein

2. All the energy source must be turned into glucose or glucose intermediate

2. Carbohydrates

1. Disaccharides and polysaccharides are degraded/hydrolyzed into monosaccharides

3. Fats

1. Stored in adipose tissues in form of triglyceride

2. When needed, it is hydrolyzed by lipase to fatty acids and glycerol

3. Glycerol

1. Must first be converted into PGAL, glycolytic intermediate

4. Fatty acid

1. Must first be activated in the cytoplasm

1. Requires 2 ATP

2. Taken into mitochondria, then with series of beta-oxidation cycle, it'd be converted into 2-carbon fragments

3. The carbon fragments are then converted into acetyl CoA

4. The acetyl CoA then enters the TCA (tri-carboxylic acid) cycle

5. With each round of beta-oxidation, 1 NADH and 1 FADH2 are generated

4. Proteins

1. Body degrades protein only when there aren't any carbs or fat around

2. Amino acids undergo transamination reaction where they lose an amino group to form alpha-keto acid

3. The carbon atom are converted into Acetyl CoA, pyruvate, or an intermediate of the Citric Acid acyle.

1. This then produces ATP

4. Oxidative deamination

1. Removes ammonia molecule directly from amino acid

Respiration in Invertebrates

1. Unicellular and Simple Multicellular Organisms

1. Protozoa and Hydra

2. Every cell in contact with external environment (or internal)

3. Gases exchanged directly between cell via simple diffusion

2. Annelids

1. Mucus secreted provides surface for gas exchange via diffusion

2. Circulatory system brings O2 to cells and waste products such as CO2 back to skin

3. Arthropod

1. They have series of respiratory tubules called tracheae

1. Branches of these reaches every cell

2. Tubes open to the surface in openings called spiracles

3. Gas exchange via diffusion with the spiracles

4. The efficiency of this system allows insects to have inefficient open circulatory system

Respiration in Humans

1. General

1. Trachea branches off into 2 large passage ways called bronchi

2. Bronchi branches off into bronchioles

1. The air is brought to the alveoli, millions of them, where gas exchange occurs

3. The complete passage goes > nose > pharynx (throat) > larynx > trachea > bronchi > bronchioles > alveoli

2. Ventilation

1. When you breathe in, the air comes in through the nose and mouth and is pulled through the wind pipe or trachea

1. Diaphragm contracts = lung capacity grows = breathing in (inhalation)

2. Diaphragm expands = lung capacity shrinks = breathing out (exhalation)

3. Control of Ventilation

1. Regulated by neurons located in medulla oblongata

1. Rhythmic discharges stimulate the intercoastal muscles and diaphragm to contract

2. If partial pressure of carbon dioxide increases, the medulla oblongata stimulates increase in rate of ventilation

4. Gas Exchange

1. Occurs in the pulmonary capillaries with simple diffusion across the capillaries wall

2. Basically, with partial pressure, O2 is moved into the red blood cell, and CO2 is released out

Respiration in Plants

1. General

1. Happens day and night

2. Photosynthesis happens only in the day

3. Plants undergo aerobic respiration just like animals

4. Gases diffuse through air opening called stomata of leaves

1. Or lenticels of woody stem