Cellular Metabolism and Carbohydrate Catabolism

Flashcards covering cellular metabolism, aerobic and anaerobic glycolysis, fates of pyruvate, the TCA cycle, oxidative phosphorylation, and metabolic regulation based on lecture notes.

What is cellular metabolism?

The sum of all chemical reactions occurring in a cell, a tissue, or a body.

What is the primary difference between catabolic and anabolic pathways?

Catabolic pathways break down complex molecules to release energy, whereas anabolic pathways require energy to synthesize larger molecules from smaller units.

What common metabolic intermediate do basic products of digestion process into for full oxidation in mitochondria?

$$\text{Acetyl-CoA}$$

What are the two modes of cell-to-cell (intercellular) metabolic communication?

Direct cell surface contact/gap junctions and chemical signaling via hormones or neurotransmitters.

Where in the cell does glycolysis occur?

In the cell cytosol of all tissues.

What is the net yield of products from glycolysis per molecule of glucose?

2 pyruvate, 2 $\text{NADH}$, and 2 $\text{ATP}$.

What are the two phases of glycolysis shown in this summary breakdown?

The energy-investment phase and the energy-generation phase.

Under anaerobic conditions in eukaryotic cells, what enzyme converts pyruvate to lactate?

Lactate dehydrogenase (LDH).

Why is the reduction of pyruvate to lactate critical during anaerobic glycolysis?

It regenerates $\text{NAD}^+$ from $\text{NADH}$, which is essential for glycolysis to continue producing $\text{ATP}$.

What tissues or cell types rely on anaerobic glycolysis for energy?

Cells lacking mitochondria (erythrocytes), tissues with low mitochondria density/poor vascularization (cornea, lens), and white fibers of skeletal muscle during quick energy demands.

How can the liver utilize lactate produced during anaerobic glycolysis?

The liver can convert lactate back into glucose via the Cori cycle and gluconeogenesis, or convert it to pyruvate via LDH for entry into the TCA cycle as $\text{Acetyl-CoA}$.

What enzyme complex catalyzes the conversion of pyruvate to acetyl-CoA inside the mitochondria under aerobic conditions?

Pyruvate dehydrogenase complex (PDHC).

What are the four primary fates of pyruvate depending on metabolic conditions?

1. Reduction to lactate (LDH)
2. Oxidative decarboxylation to $\text{Acetyl-CoA}$ (PDHC)
3. Carboxylation to oxaloacetate (Pyruvate carboxylase)
4. Transamination to alanine (ALT/SGPT)

In which sub-mitochondrial compartment does the TCA (Krebs) cycle take place?

The mitochondrial matrix.

What components make up oxidative phosphorylation (OXPHOS)?

The Electron Transport Chain (ETC) and $\text{ATP}$ synthase.

What is the final electron acceptor in the Electron Transport Chain (ETC)?

Oxygen ($\text{O}_2$), which combines with electrons and $\text{H}^+$ to form water ($\text{H}_2\text{O}$).

Which components of the mitochondrial Electron Transport Chain are mobile electron carriers?

Coenzyme Q (CoQ) and cytochrome c (Cyt c).

Which respiratory chain complex is inhibited by carbon monoxide, hydrogen sulfide, and cyanide?

Complex IV.

What chemical agents inhibit Complex I and Complex II of the Electron Transport Chain?

Complex I is inhibited by barbiturates and rotenone; Complex II is inhibited by malonate, carboxin, and TTFA.

What is the action of uncouplers in oxidative phosphorylation?

They dissociate oxidation (ETC) from phosphorylation ($\text{ATP}$ synthase), dissipating the proton gradient as heat rather than generating $\text{ATP}$.

Which molecules act as allosteric or metabolite inhibitors of the TCA cycle and OXPHOS?

$\text{ATP}$, $\text{NADH}$, and Citrate.

Which molecules stimulate the TCA cycle and OXPHOS?

Glucose, $\text{Acetyl-CoA}$, $\text{ADP}$, and $\text{NAD}^+$.

What is the total overall ATP yield from the complete oxidation of one glucose molecule during aerobic cellular respiration?

36 $\text{ATP}$ (comprising 2 $\text{ATP}$ net from Glycolysis, 2 $\text{ATP}$ from Krebs Cycle, and 32 $\text{ATP}$ from Oxidative Phosphorylation).

Which enzyme complex circled in the diagram produces ATP using an electrochemical proton gradient?

ATP-Synthase