Exam 2 - BIO183

What is an autotroph?

Organism that produce its own organic molecule through photosynthesis

What is a heterotroph?

Organism that lives off consuming others

What is cellular respiration?

A series of reactions that:

• are oxidations (loss of electrons)

• are also dehydrogenations (lost electrons accompanied by hydrogen)

What is the final electron receptor for aerobic respiration?

• Oxygen (O2)

What is the final electron acceptor for anaerobic respiration?

• Inorganic molecule (not O2)

What is the final electron acceptor in fermentation?

• organic molecule

How are cells able to make ATP?

(Hint: it’s 2 phosphorylations)

1. Substrate-level phosphorylation

2. Oxidative phosphorylation

What are the complete stages (in order) for the oxidation of glucose?

1. glycolysis

2. pyruvate oxidation

3. Krebs cycle

4. electron transport chain & chemiosmosis.

What does glycolysis do, and what does it produce?

• Converts glucose to pyruvate

• Produces 2 molecules of pyruvate and has a net production of 2 ATP molecules by substrate-level phosphorylation

• 2 NADH produced by reduction of NAD⁺

Where does glycolysis occur?

• Cytoplasm

What is the rate-limiting enzyme within glycolysis?

• Phosphofructokinase

What enzyme catalyzes the reaction in Pyruvate Oxidation?

• pyruvate dehydrogenase

What is the purpose of pyruvate oxidation? What does it produce?

• Pyruvate oxidation acts as a bridge as it connects glycolysis to the Krebs cycle

• Converts the carbon pyruvate molecules produced in the cytoplasm into Acetyl-CoA molecules that proceed to krebs cycle

• Its products include

  • 1 CO2

  • 1 NADH

  • 1 Acetyl-CoA (consisting of 2 carbons attached to coenzyme A)

Where does pyruvate oxidation occur?

• Mitochondria

What is the purpose of the Krebs cycle? What does it produce?

• The Krebs cycle oxidizes the acetyl group from pyruvate

• Products per acetyl CoA molecule include

  • release 2 molecules of CO₂

  • reduces 3 NAD⁺ to 3 NADH

  • reduces 1 FAD to FADH₂

  • Produce 1 ATP

  • regenerate oxaloacetate

Where does the Krebs cycle occur?

• Matrix of mitochondria

What is established with the Electron Transport Chain?

• A proton gradient

What is the theoretical glucose energy yield at the end of the oxidation of gluclose?

• 38 ATP per glucose

What does Oxidation-fermentation do?

• Reduces organic molecules in order to regenerate NAD⁺

• Pyruvate is converted into ethyl alcohol

Where does ethanol fermentation typically occur? What is produced?

• Occurs in yeast

• CO_2, ethanol, and NAD⁺ are produced.

Where does lactic acid fermentation typically occur? What is produced.

• Occurs in animal cells (especially muscles)

• electrons are transferred from NADH to pyruvate to produce lactic acid

Where does the Electron Transport Chain take place?

• Inner membrane of mitochondria

What is NAD⁺?

• Electron carrier that produces NADH in glycolysis, Pyruvate Oxidation, and Krebs cycle.

What is FAD?

• Electron carrier that produces FADH2 during the Krebs cycle

What is the difference between Substrate-level and oxidative phosphorylation?

Substrate-level

• Transferring a phosphate directly to ADP from a high energy substrate, but produces little ATP

Oxidative

• Use of ATP synthase and energy derived from proton (H+) to make ATP, producing ATP more efficiently.

What are the substrates in glycolysis?

Primary: glucose

Along with

• 2 NAD⁺

• 2 ADP

• 2 inorganic phosphates

What are the substrates in pyruvate oxidation?

• Pyruvate

• NAD⁺

• Coenzyme A

What are the substrates/inputs in the Krebs cycle?

• Acetyl-CoA

• H₂O

• Oxaloacetate (OAA)

• Electron receptors (NAD⁺ and FAD)

• ADP and inorganic phosphate

What are the substrates in the Electron Transport Chain?

• NADH

• FADH₂

• O₂

• ADP and inorganic phosphate

• Protons (H⁺)

What is a reduction reaction?

• The process in which molecules gain electrons, often accompanied by hydrogen ions

What are the major electron carrier reduction reactions in Cellular Respiration?

NAD⁺ —→ NADH

FAD —→ FADH₂

What is the oxygen reduction at the end of the Electron Transport Chain?

O₂—→ H₂O

What are the reduction reactions in fermentation if oxygen is absent?

Pyruvate —→ Lactate

Acetaldehyde —-→ Ethanol

Where does the NAD⁺ to NADH reduction reaction occur?

• Glycolysis

• Pyruvate transition

• Krebs cycle

Where does the FAD to FADH₂ reaction occur?

• The Krebs cycle

• ***Enters ETC at a lower energy level***

What are the alternate sources of energy in cellular respiration?

If glucose is unavailable, the body will utilize

• Fats

  • Glycerol

  • Fatty acids

• Proteins

  • Pyruvate

  • Acetyl-CoA

• Other carbohydrates

  • Glycogen

  • Fructose and Galactose

What is the number of CO2 molecules given off per glucose molecule in glycolysis only?

0

What is the number of ATP molecules formed per glucose molecule in the Krebs cycle only?

2

What is the number of FADH2 molecules formed per glucose molecule in the Krebs cycle only?

2

What is the number of ATP made by substrate-level phosphorylation per glucose molecule during the four stages of cellular respiration (net)?

4

What is the number of CO2 given off per glucose molecule in the Krebs cycle only?

4

What is the number of steps in the glycolytic pathway?

10

What is the number of NADH produced per glucose molecule in total

10

What is the waxy, waterproof layer of a leaf that covers the upper epidermis and prevents evaporation?

Cuticle

What is the single, transparent layer of cells inside a leaf that protects the inner tissues?

Epidermis

What allows gas exchange in the lower epidermis and is regulated by guard cells that open/close in response to water?

Stomata

What are the organelles containing chlorophyll that capture light energy to convert CO₂ and water into glucose?

Chloroplasts

What is photosynthesis divided into?

• Light-dependent reactions

• Carbon fixation reaction

What happens in a light-dependent reaction?

• Capture energy from sunlight

• Produces ATP and reduces NADP⁺ to NADPH

What happens in a carbon fixation reaction?

• use ATP and NADPH to synthesize organic molecules from CO₂

what is the internal membrane arranged in flattened sacs referred to as?

• Thylakoid membrane

What does the thylakoid membrane contain?

• Chlorophyll and other pigments

What are stacks of thylakoid membrane referred to as?

• Grana

What is the semiliquid substance surrounding thylakoid membranes, where carbon fixation occurs, referred to as?

• Stroma

What consist of xylem (that transports water from roots) and phloem (transports sugars away) in a leaf?

• Vascular bundles (veins)

Where do light-dependent reactions take place in the chloroplast?

• Thylakoid membrane

Where does carbon fixation/calvin cycle reaction take place in the chloroplast?

• Stroma

What are the substrates in a light-dependent reaction?

• H₂O (water)

• ADP + inorganic molecule

• NADP⁺

What are the end products in a light-dependent reaction

• ATP

• NADPH

• O₂ (oxygen released as waste)

What are the substrates in a carbon fixation reaction?

• CO₂

• _ATP

• _NADPH

What are the end products of the carbon fixation reaction?

• G3P

• ADP + inorganic molecule

• NADP⁺

What is the sequence of events in Light reactions?

1. Light absoption

   1. Chlorophyll in Photosystem II (PSII) absorbs light.

2. Water splitting (photolysis)

   1. Water splits into:

   2. 2H⁺ + 2e⁻ + ½O₂

   3. Oxygen is released.

3. Electron transport chain

   1. Excited electrons move through carriers in the thylakoid membrane

4. Proton gradient formation

   1. H⁺ ions accumulate in the thylakoid lumen.

5. ATP synthesis

   1. Protons move through ATP synthase.

   2. ADP + Pi → ATP

6. Photosystem 1 activation

   1. Light excites electrons again in PSI

7. NADPH formation

   1. Electrons reduce NADP⁺ → NADPH

What is the sequence of events in the carbon fixation reaction (or dark cycle.)

1. Carbon Fixation

• CO₂ combines with RuBP (5-carbon molecule)

• Enzyme RuBisCO catalyzes reaction

• Forms 2 molecules of 3-phosphoglycerate (PGA)

2. Reduction

• ATP and NADPH convert PGA → G3P

3. Regeneration of RuBP

• G3P is used to regenerate RuBP

Where does ATP feed into/used for?

• Used in the calvin cycle

Where does NADPH product feed into/used for

• Provides reducing power in calvin cycle

Where does O₂ feed into/used for

• Released to the atmosphere or used in cellular respiration

Where does G3P/Glucose feed into/used for

• Used for respiration, starch storage, or cellulose synthesis.

What is the electron path in a Non-Cylic flow?

• Linear

What is the electron path in a cyclic-flow?

• Circular

What is carbon fixation within the calvin cycle?

• The incorporation of CO₂ into organic moleculles

  • First step of the calvin cycle

What is the primary photopigment in photosynthesis?

• Chlorophyll a

What are the two accessory pigments?

• Chlorophyll

• Carotenoids

What does the photopigment, chlorophyll a do?

• Absorbs violet-blue and red light

What does the accessory pigment, chlorophyll b do?

• increase the range of light wavelengths that can be used in photosynthesis

What does the accessory pigment, carotenoids do?

• Acts as antioxidations or photoprotectors.

What is photorespiration?

• The oxidation of RuBP by the addition of O₂

• Favored in hot conditions as plants close their stomata to reduce water loss

  • Less CO₂ enters leaf

  • O₂ begins to accumulate

  • They both begin to compete for the active site on RuBP

During the Calvin cycle, energy is needed, what is the energy supplied from?

• 18 ATP molecules

• 12 NADPH molecules

What is the carbon fixation reaction catalyzed by?

• Rubisco

To build carbohydrates, what do cells need?

1. Energy (atp from light-dependent reaction)

2. Reduction potential (NADPH from photosystem I)

Where is ATP synthase embedded in during Light-Dependent Reactions?

• Thylakoid membrane

What is an absorption spectrum?

• The range and effciency of photons a pigment is capable of absorbing

What role does the ligand serve in cell communication?

• Acts as a signaling molecule

What role does the receptor protein play in cell communication?

• Binds the ligand

  • May be on the plasma membrane or within the cell

What 2 things does cell communication require?

• A ligand

• A receptor protein

What are the 3 types of cell communication?

• Direct contact

• Paracrine

• Endocrine/Hormone signaling

What is the process of direct contact in cell communication?

• Molecules on the surface of one cell are recognized by receptors on adjacent cell

What is the process of paracrine signaling in cell communication?

• Signal released from a cell has an effect on neighboring cells

What is the process of endocrine/hormone signaling in cell communication?

• Hormones released from a cell affect other cells throughout the body

What is the sequence of events with ligands, receptors, and cell response

1. Reception

   1. Ligand binds receptor —> receptor activates

2. Transduction

   1. Receptor bonds to G proteins

   2. G protein acts as a switch (turned on by receptor)

   3. It produces a second messenger

3. Response

   1. Second messenger generates cellular response

   2. Cell changes activity in response to messenger (gene expression, enzyme activity, secretion, etc)

4. Termination

   1. Signals turned off to reset cell

What is phosphorylation in cell communication?

• A common way to change the activity of a protein

What is protein kinase in cell communication?

• An enzyme that adds a phosphate to a protein

What is phosphatase in cell communication?

• An enzyme that removes a phosphate from a protein

What structure do steroid hormones have, and where do they cross into in the plasma membrane?

• Have a nonpolar, lipid-soluble structure

• Cross the plasma membrane to a steroid receptor

What are the 3 membrane receptor/protein ligand types?

1. Channel linked receptors

2. Enzymatic receptors

3. G Protein-coupled receptor

What does hyperpolarization mean?

• Cell membrane is more polarized, more negative

What does depolarization mean?

• Cell membrane less polarize, less negative relative to surrounding solution

Changes in membrane potential are changes in the degree of _______?

Polarization

What is a common example of a effector protein producing a second messenger?

• One common effector protein is adenylyl cyclase producing cAMP as a second messenger.

What is the difference between steroid and protein ligands?

• Steroid ligands are lipid based and pass through cell membranes

• They influence gene expression and protein synthesis

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• Protein ligands are water-soluble and cannot pass through cell membranes

• Bind to receptors on cell surface to trigger a signaling cascade within the cell

What are channel linked receptors?

• ion channel that opens in response to a ligand