unit 2 week 2 pt 2 Flashcards
What type of organisms first dominated Earth?
Earth was initially ruled by anaerobes, organisms that captured and utilized energy through oxygen-independent (anaerobic) metabolism, such as glycolysis and fermentation.
What are aerobes?
Aerobes are organisms that became dependent on oxygen for energy production.
-notice: ANaerobes are independent on oxygen
In eukaryotic cells, where does oxygen-dependent energy extraction (aerobic respiration) occur?
It occurs in a specialized organelle called the mitochondrion.
aerobic respiration
a cellular process that uses oxygen to break down glucose and other nutrients, releasing energy in the form of ATP (adenosine triphosphate), carbon dioxide, and water.
-happens @ mitochondria
-key stages:
Glycolysis: Glucose is broken down into pyruvate in the cytoplasm, producing a small amount of ATP and NADH.
Krebs Cycle (Citric Acid Cycle): Pyruvate is further processed in the mitochondria, producing more ATP, NADH, and FADH2.
Electron Transport Chain: NADH and FADH2 donate electrons, and this process generates a large amount of ATP and water.
How does mitochondrial structure vary?
Mitochondria can exist as individual, bean-shaped organelles or a highly branched network.
What are mitochondrial fusion and fission?
Mitochondrial fusion is when mitochondria merge together, while mitochondrial fission is when mitochondria split into two.
What induces mitochondrial fission?
Thin tubules from the endoplasmic reticulum (ER) help induce mitochondrial fission.
-details: the process where mitochondria divide, is induced by the recruitment and activation of the dynamin-related protein 1 (Drp1), which is triggered by various factors including mechanical forces, post-translational modifications, and interactions with other cellular structures like the endoplasmic reticulum (ER).
How do fusion and fission affect mitochondrial shape?
More fusion than fission leads to elongated and interconnected mitochondria, while more fission than fusion results in more numerous and distinct mitochondria.
How do mitochondria generate ATP?
Mitochondria generate ATP through oxidative phosphorylation, where energy from electron transport is used to power ATP synthesis.
Besides ATP production, what other functions do mitochondria have?
Mitochondria play key roles in the uptake and release of calcium ions and the synthesis of various substances.
What are the two membranes that form the outer boundary of a mitochondrion?
The outer mitochondrial membrane and the inner mitochondrial membrane.
What is the function and composition of the outer mitochondrial membrane?
It completely encloses the mitochondrion, serving as its outer boundary, composed of ~50% lipid by weight, and contains enzymes involved in oxidation of epinephrine, degradation of tryptophan, and elongation of fatty acids.
-very permeable to small molecules
What are the characteristics of the inner mitochondrial membrane?
It contains more than 100 different polypeptides, has a high protein-to-lipid ratio (more than 3:1 by weight), is virtually devoid of cholesterol but rich in cardiolipin, and is highly impermeable.
What are the two major domains of the inner mitochondrial membrane?
The inner boundary membrane and cristae.
What are cristae junctions?
Cristae junctions are specialized regions that connect cristae to the inner boundary membrane and help regulate mitochondrial function.
-Cristae membranes are folds in the inner membrane of mitochondria, increasing the surface area for ATP production and housing the complexes of the respiratory chain and ATP synthase.
What are the two compartments within the mitochondrion, created by its membranes?
The matrix and the intermembrane space.
How is the outer mitochondrial membrane similar to bacterial membranes?
It is thought to be homologous to the outer membrane found in certain bacterial cell walls and both contain porins.
How do porins in the outer mitochondrial membrane function?
Porins are not static; they can open and close in response to cellular conditions, allowing molecules like ATP, NAD, and coenzyme A to pass through freely.
-porin: any of a class of proteins whose molecules can form channels (large enough to allow the passage of small ions and molecules) through cellular membranes.
How does the permeability of the inner and outer mitochondrial membranes compare?
The outer membrane is freely permeable due to porins, while the inner membrane is highly impermeable.
What are the key components of the mitochondrial matrix?
Enzymes, ribosomes (smaller than cytosolic ones), and circular DNA.
What is unique about mitochondrial DNA (mtDNA)?
Mitochondria have their own DNA (mtDNA), allowing them to produce their own RNAs and proteins.
What is the evolutionary origin of mitochondrial DNA?
mtDNA is a remnant of an ancient aerobic bacterium that was an ancestor of modern eukaryotic cells.
How does mitochondrial RNA polymerase compare to other RNA polymerases?
It is a single-subunit enzyme (meaning it’s made up of 1 polypeptide chain), similar to those found in bacterial viruses.
-unlike the multi-subunit RNA polymerases found in bacteria and eukaryotic nuclei
How is mtDNA useful in research?
mtDNA is widely used for studying human migration and evolution and for ancestry tracing.
Where does carbohydrate oxidation begin?
It begins in the cytosol with glycolysis, where enzymes break down glucose.
additional info:
-cytosol: the aqueous component of the cytoplasm of a cell
Carb Oxidation details:
-refers to the breakdown of carbohydrates (mainly glucose) to release energy.
-can occur through aerobic (with oxygen) or anaerobic (without oxygen) pathways.
-broader term that includes both aerobic respiration and anaerobic pathways (like fermentation).
-aerobic respiration is a specific type of carbohydrate oxidation that occurs in the presence of oxygen.
What happens during glycolysis?
Glycolysis is a 10-step pathway that converts glucose into pyruvate, producing a net of 2 ATP per glucose molecule.
How is NADH produced during glycolysis?
NADH is generated during the oxidation of glyceraldehyde 3-phosphate.
What are the two possible metabolic fates of pyruvate and NADH?
With oxygen, they enter the mitochondria for further ATP production; without oxygen, pyruvate undergoes fermentation.
How much ATP is produced under aerobic conditions?
30+ additional ATP molecules can be synthesized from pyruvate and NADH in mitochondria.
How does pyruvate enter the mitochondria?
It is transported across the inner mitochondrial membrane into the matrix.
What happens to pyruvate in the mitochondrial matrix?
Pyruvate is decarboxylated, forming a two-carbon acetyl group that binds to coenzyme A to form acetyl CoA.
What enzyme catalyzes the conversion of pyruvate to acetyl CoA?
The reaction is catalyzed by pyruvate dehydrogenase.
What is the TCA cycle, and what does it do?
The TCA cycle, also known as the Krebs cycle, is a cyclic metabolic pathway that oxidizes acetyl CoA to extract energy.
Where do the TCA cycle enzymes reside?
Most enzymes are located in the soluble phase of the mitochondrial matrix.
What is the first step of the TCA cycle?
The two-carbon acetyl group from acetyl CoA condenses with four-carbon oxaloacetate, forming a six-carbon citrate molecule.
What happens to citrate during the cycle?
Citrate undergoes a series of reactions that remove carbons one at a time, ultimately regenerating oxaloacetate.
How does the TCA cycle contribute to energy production?
The TCA cycle involves four redox reactions, transferring electrons to coenzymes.
Why is the TCA cycle important in metabolism?
The TCA cycle is a central hub for metabolism, processing all major macromolecules.
Why is the mitochondrion important for metabolism?
The mitochondrion serves as the site for the final energy-conserving steps of metabolism.
What are the primary products of the TCA cycle, and why are they important?
The main products are the reduced coenzymes NADH and FADH?, which store high-energy electrons used in the electron transport chain.
How does NADH from glycolysis enter the mitochondria for ATP production?
Electrons are transferred using two shuttle systems: the malate-aspartate shuttle and the glycerol phosphate shuttle.
What are the two major steps in ATP formation from reduced coenzymes?
Step 1: Electron Transport Chain (ETC) and Step 2: ATP Synthesis (Chemiosmosis).
How much ATP is produced per molecule of glucose?
The total ATP yield per glucose molecule is about 36 ATP.
How does ATP production vary depending on cellular activity?
The actual ATP yield depends on whether a cell primarily relies on anaerobic glycolysis or aerobic metabolism.
