Cellular Respiration and Circulatory Systems Overview

Aerobic

Involves oxygen; a metabolic process requiring oxygen to generate ATP.

Anaerobic

Occurs without oxygen; organisms or cells that utilize pathways like fermentation for energy.

Cellular respiration

The biochemical process by which cells extract energy from organic molecules, typically glucose, through multiple enzymatic reactions.

Glycolysis

The first stage of cellular respiration, breaking down glucose into pyruvate while producing a small amount of ATP and NADH.

Phosphorylation

The addition of a phosphate group to a molecule, crucial for ATP synthesis.

Oxidation

The loss of electrons from a molecule, often releasing energy.

Reduction

The gain of electrons by a molecule.

Catabolic

Processes that break down molecules to release energy (e.g., cellular respiration).

Anabolic

Processes that build complex molecules from simpler ones, usually requiring energy (e.g., photosynthesis).

Metabolic water

Water produced as a byproduct of metabolic reactions, including the electron transport chain in cellular respiration.

Cell metabolism

The sum of all biochemical reactions in a cell, including both anabolic and catabolic pathways.

Glycolysis Input

Glucose

Glycolysis Output

Pyruvate, ATP, NADH

Pyruvate Oxidation Input

Pyruvate

Pyruvate Oxidation Output

Acetyl-CoA, CO₂, NADH

Citric Acid Cycle Input

Acetyl-CoA

Citric Acid Cycle Output

CO₂, ATP, NADH, FADH₂

Electron Transport Chain Input

NADH, FADH₂, O₂

Electron Transport Chain Output

ATP, H₂O

Cellular respiration equation

C6H12O6 + 6O2 -> 6CO2 + 6H2O + 36 or 38 ATP

ATP Cycle

ATP is used for energy-requiring processes and regenerated through phosphorylation.

NADPH Cycle

Involved primarily in anabolic reactions like photosynthesis; different from NADH in cellular respiration.

Substrate-level phosphorylation

Direct transfer of phosphate to ADP (occurs in glycolysis and Krebs cycle).

Oxidative phosphorylation

ATP synthesis using energy from the electron transport chain.

Gas Exchange

The process of moving oxygen into cells and removing carbon dioxide.

Bulk Flow

The movement of fluids or gases driven by pressure differences (e.g., blood circulation or air movement).

Ventilation

The movement of air into and out of the lungs.

Circulation

The transport of fluids (blood, lymph) through an organism.

Pressure

The force exerted by a fluid or gas.

Partial Pressure

The pressure exerted by a single gas within a mixture.

Resistance

The opposition to flow in ventilation or circulation (e.g., airway constriction reduces airflow).

Oxygen Requirement in Eukaryotes

Oxygen is an electron acceptor.

Bulk Transport Mechanisms

Large organisms, including mammals, birds, and reptiles, use bulk transport via circulatory systems to move oxygen efficiently.

Insect Oxygen Movement

Insects use tracheal systems for bulk oxygen movement.

Aquatic Oxygen Transport

Aquatic organisms, like fish, use gills and circulatory transport.

Partial Pressure Calculation

Px=(fraction of gas)×(total atmospheric pressure).

Net Diffusion of Gas

Follows concentration gradient high pp to low pp.

Diffusion vs. Bulk Flow

Diffusion moves gases passively, dependent on concentration gradients; Bulk flow moves gases actively, driven by pressure changes (e.g., breathing).

Factors Increasing Bulk Flow

Increase: Higher pressure, larger diameter pathways, lower resistance.

Factors Decreasing Bulk Flow

Decrease: Narrower pathways, higher viscosity, increased resistance.

Diffusion Pros

Simple, energy-efficient.

Diffusion Cons

Slow over long distances.

Bulk Transport Pros

Fast, efficient.

Bulk Transport Cons

Requires energy, complex systems.

Inhalation

The intake of air into the lungs or respiratory system.

Exhalation

The expulsion of air from the lungs or respiratory system.

Countercurrent Exchange

A mechanism in which fluids flow in opposite directions to maximize gas exchange efficiency (e.g., fish gills).

Tidal Ventilation

Air moves in and out of the lungs in the same pathway (common in mammals).

Crosscurrent Exchange

Air flows perpendicular to blood flow to increase oxygen absorption (seen in bird lungs).

Fish Gills

Highly vascularized structures allowing gas exchange via countercurrent flow.

Insect Tracheal System

A network of tubes directly delivering oxygen to cells through spiracles.

Amphibian Respiratory System

Uses lungs, skin, and sometimes the buccal cavity for respiration.

Bird Lungs

Rigid lungs with air sacs and a unidirectional airflow mechanism.

Mammalian Lungs

Spongy lungs relying on tidal ventilation for gas exchange.

Fish Ventilation and Gas Exchange

Water enters through the mouth and flows over the gills; Oxygen diffuses into the blood while carbon dioxide is expelled; Countercurrent exchange ensures maximum oxygen uptake.

Air Respiration

The process of breathing air to obtain oxygen.

Water Respiration

The process of extracting oxygen from water.

Oxygen Content

The amount of oxygen present in a given volume of air or water.

Energy Requirement

The amount of energy needed for an organism's metabolic processes.

Efficiency

The effectiveness of a respiratory system in extracting oxygen.

Ventilation in the insect respiratory system

Air enters spiracles, flowing through tracheal tubes. Muscle contractions help move gases internally. Diffusion at the cellular level enables gas exchange.

Mammalian lung ventilation

Air moves in and out the same path (tidal ventilation).

Bird lung ventilation

Air moves through a one-way system using air sacs to maintain a continuous flow.

Respiratory volume calculation

Respiratory volume = Tidal Volume × Breaths.

Gas exchange in fish

Uses countercurrent exchange for oxygen uptake.

Gas exchange in birds

Uses crosscurrent exchange for oxygen uptake.

Gas exchange in mammals

Uses tidal ventilation for oxygen uptake.

Hematocrit

The proportion of blood volume occupied by red blood cells, often used as an indicator of oxygen-carrying capacity.

Solubility

The ability of a gas (like oxygen or carbon dioxide) to dissolve in a liquid (blood plasma).

Oxygenated blood

Blood that contains oxygen, typically transported by arteries.

Deoxygenated blood

Blood that has released oxygen and carries carbon dioxide, usually found in veins.

Tetramer

A protein structure composed of four subunits (e.g., hemoglobin has four subunits).

Monomer

A single molecular unit (e.g., myoglobin is a monomeric oxygen-binding protein).

Cooperative Binding

A mechanism where oxygen binding to one hemoglobin subunit increases the affinity of other subunits for oxygen.

Reversible Binding

Oxygen can bind to and detach from hemoglobin depending on environmental conditions (e.g., oxygen levels in tissues and lungs).

Oxygen Diffusion

Oxygen moves from alveoli (high oxygen pressure) into pulmonary capillaries (low oxygen pressure).

Carbon Dioxide Removal

Carbon dioxide diffuses from capillaries into alveoli, where it is exhaled.

Plasma

Contains water, nutrients, hormones, and dissolved gases.

Red Blood Cells (Erythrocytes)

Transport oxygen via hemoglobin.

White Blood Cells & Platelets

Immune defense and clotting function.

Importance of cooperative binding

Ensures efficient oxygen uptake in the lungs and facilitates oxygen release in tissues where it is needed.

Hemoglobin family of molecules

Certain bacteria contain hemoglobin-like proteins for oxygen binding; some invertebrates use hemocyanin; vertebrates use hemoglobin.

Structural anatomy of hemoglobin

Tetrameric Protein with four subunits, each binding one oxygen molecule. Can carry up to four oxygen molecules per hemoglobin.

Importance of reversible binding

Allows oxygen pickup in lungs and oxygen release in tissues; carbon dioxide binding competes with oxygen transport in red blood cells.

O2 loading (binding)

High oxygen pressure in the lungs causes hemoglobin to bind oxygen.

O2 unloading (release)

Low oxygen pressure in the tissues leads to the release of oxygen from hemoglobin.

Myoglobin

A protein with higher oxygen affinity than hemoglobin, storing oxygen in muscle tissues.

Transport of CO2

CO₂ dissolves in plasma, with the majority converted to bicarbonate (HCO₃⁻) via carbonic anhydrase.

Carbonic anhydrase

An enzyme that catalyzes the conversion of CO₂ to bicarbonate in the bicarbonate buffering system.

Hemolymph

The circulatory fluid found in organisms with open circulatory systems, serving as a combined transport system for nutrients and waste.

Blood

The specialized circulatory fluid in closed systems, consisting of plasma, red and white blood cells, and platelets.

Vasodilation

The widening of blood vessels, increasing blood flow and reducing blood pressure.

Vasoconstriction

The narrowing of blood vessels, decreasing blood flow and increasing blood pressure.

Filtration

The process by which plasma passes from capillaries into the interstitial fluid due to pressure differences.

Reabsorption

The movement of fluids back into the blood, helping maintain homeostasis.

Open circulatory system structure

Hemolymph is pumped by the heart into open spaces (hemocoel), where it directly bathes organs.

Open circulatory system lineages

Found in arthropods (insects, crustaceans) and many mollusks.

Advantages of open circulatory system

Requires less energy and has a simple system design.

Disadvantages of open circulatory system

Less efficient oxygen delivery and slow circulation.

Closed circulatory system structure

Blood is confined within vessels and transported by a heart through a network of arteries, veins, and capillaries.