Midterm 2 Review: Cellular Organelles and Functions

Endosymbiosis

The theory that mitochondria and chloroplasts evolved from free-living prokaryotes.

Double Membranes

Both mitochondria and chloroplasts have double membranes, indicating they originated through an engulfment process.

Circular DNA

Both organelles contain circular DNA, resembling bacterial genomes, supporting their evolutionary origin.

Ribosomes in Mitochondria and Chloroplasts

These ribosomes are similar in size and structure to prokaryotic ribosomes and are sensitive to antibiotics affecting bacteria.

Lysosomal Proton Pump

Responsible for maintaining the acidic environment within lysosomes.

Lysosomal pH Shift

If the pH shifts toward neutral, lysosomal enzymes become inactive or less efficient, failing to degrade macromolecules.

Importance of Acidic pH

Lysosomal enzymes, such as proteases, are only active at low pH, and a neutral pH leads to incomplete degradation of cellular waste.

Cellular Waste Accumulation

The inability to maintain an acidic lysosomal environment results in a buildup of cellular waste and damaged organelles.

Impact on High-Turnover Tissues

Failure of lysosomes to degrade material may cause progressive cell death in tissues like the liver, kidneys, and immune cells.

Neurodegenerative Diseases

In neurons, the inability to clear protein aggregates could contribute to diseases like Alzheimer's or Parkinson's.

Oxygen in Electron Transport Chain

Oxygen acts as the final electron acceptor, combining with protons to form water and creating a proton gradient for ATP synthesis.

Consequences of Oxygen Unavailability

Without oxygen, the ETC halts, leading to a collapse of the proton gradient and a drop in cellular energy levels.

Anaerobic Glycolysis

In low-oxygen environments, cells switch to anaerobic glycolysis to generate energy, producing 2 ATP per glucose.

Lactic Acid Fermentation

In animals, pyruvate is converted into lactate during intense exercise when oxygen supply is insufficient.

Oxidative Phosphorylation

A process in mitochondria where ATP is produced using the proton gradient created by the electron transport chain.

ATP Synthase

An enzyme that synthesizes ATP using the proton gradient generated during oxidative phosphorylation.

Proton Gradient

A difference in proton concentration across the inner mitochondrial membrane that drives ATP synthesis.

Cellular Homeostasis

The balance of cellular processes that can be disrupted by accumulated waste products.

Cell Death

Progressive cell death can occur due to the accumulation of waste and damaged organelles.

Inflammatory Responses

Triggered by undigested waste accumulation, leading to further tissue damage and dysfunction.

Electron Transport Chain (ETC)

A series of complexes in mitochondria that transfer electrons and pump protons to create a gradient for ATP production.

NADH and FADH2

Reduced cofactors that donate electrons to the electron transport chain during cellular respiration.

Citric Acid Cycle

A critical metabolic pathway that slows down or stops when NADH and FADH2 cannot donate their electrons.

Energy-Demanding Tissues

Tissues like the brain that are particularly affected by drops in cellular energy levels.

Proton Pump

A mechanism in lysosomes that maintains their acidic environment, crucial for enzyme activity.

Macromolecule Degradation

The process of breaking down large biological molecules, which is impaired when lysosomal function is compromised.

Cellular Dysfunction

A state where cellular processes are disrupted, potentially leading to disease.

Mitochondria

Organelles where oxidative phosphorylation occurs, generating ATP through a proton gradient in the inner mitochondrial membrane.

Chloroplasts

Organelles where photophosphorylation occurs, generating ATP through a proton gradient in the thylakoid membrane.

Permeoxin

A fictional pore-forming toxin that disrupts the selective permeability of plasma membranes.

Selective Permeability

The ability of a plasma membrane to allow certain substances to pass while blocking others.

Ion Gradient

The difference in ion concentration across a membrane that is crucial for maintaining electrochemical gradients.

Osmolarity

The concentration of solute particles in a solution, affecting water movement across membranes.

ATP/Metabolism

The process by which cells produce ATP, relying on ion gradients for secondary active transport.

Signal Transduction

The process by which cells respond to signals, often involving ion fluxes across membranes.

Cytoskeleton

A dynamic network of filaments that contributes to cell shape and movement.

Active Transport

The movement of substances against their concentration gradient, requiring ATP.

Passive Transport

The movement of substances down their concentration gradient without the use of energy.

Hormone Receptors

Proteins that bind hormones, leading to different cellular responses based on receptor type.

Fluorescent Protein Staining

A technique used to visualize ribosomes, which can show distribution across the cell.

Tight Junctions

Structures that create a nearly impermeable barrier between neighboring cells, preventing leakage.

Carbon Dioxide (CO₂)

The final carbon molecule produced when one glucose molecule is completely oxidized.

Glycolysis

The process of breaking down glucose into pyruvate, producing ATP and NADH.

Pyruvate Oxidation

The conversion of pyruvate into acetyl-CoA, releasing CO₂ and generating NADH.

Substrate-Level Phosphorylation

The direct generation of ATP through the transfer of a phosphate group from a substrate to ADP.

Chemiosmosis

The indirect synthesis of ATP driven by a proton gradient across a membrane via ATP synthase.

Photophosphorylation

The process occurring in chloroplasts where ATP is produced using light energy to create a proton gradient.

Glycolysis and Citric Acid Cycle

Cellular processes where substrate-level phosphorylation occurs.

Oxidative Phosphorylation and Photophosphorylation

Processes where chemiosmosis is utilized to produce ATP.