Bioenergetics and Redox Reactions

Study Notes

Reduction involves a gain of electrons, crucial for energy transfer in processes such as cellular respiration.
Cellular respiration transfers electrons from nutrients like glucose to oxygen, producing ATP.

Ligation Reactions: Use ATP to form bonds between molecules; example includes the synthesis of oxaloacetate from pyruvate and CO2.
Isomerization Reactions: Rearrange atoms within a molecule; in glycolysis, glucose-6-phosphate is converted to fructose-6-phosphate.
Group Transfer Reactions: Transfer a chemical group; phosphorylation is a common example.
Hydrolytic Reactions: Use water to break bonds, such as converting peptides into amino acids or ATP into ADP.

Carbon’s oxidation state varies with the number of electrons it has; more reduced carbons (like hydrocarbons) store more energy.
Nutrient oxidation releases energy, which is converted into ATP by cells.

Beyond ATP, creatine phosphate, acetyl-CoA, and NADH are vital for energy storage and transfer.
Creatine phosphate acts as an energy reserve in muscles; acetyl-CoA is crucial in many metabolic pathways.
NADH and FADH2 function as electron carriers in oxidative phosphorylation.

Carbohydrates serve as energy sources, structural components, and signaling molecules.
Types include:
- Monosaccharides: Single sugar units (e.g., glucose, fructose).
- Disaccharides: Two sugar units (e.g., sucrose, lactose).
- Oligosaccharides: Chains of 3-10 monosaccharides.
- Polysaccharides: Long chains (e.g., starch, glycogen).

Primarily occurs in the liver.
Key steps include:
- Phosphorylation by fructokinase to form fructose-1-phosphate.
- Cleavage by aldolase B into glyceraldehyde and DHAP.
- Glyceraldehyde conversion to glyceraldehyde-3-phosphate for glycolysis.
Excessive fructose intake can lead to metabolic disorders like fructose intolerance.

Also metabolized in the liver.
Steps include:
- Phosphorylation to form galactose-1-phosphate.
- Conversion to UDP-galactose via specific enzymes.
- UDP-galactose to UDP-glucose for further metabolism.
Galactosemia, a genetic disorder, results from deficiencies in processing galactose, leading to severe health issues.

Composed of two monosaccharide units; primary types include sucrose, lactose, and maltose.
Key hydrolysis reactions convert these into monosaccharides:
- Sucrose produces glucose and fructose.
- Lactose yields glucose and galactose.
- Maltose generates glucose.
Lactose intolerance stems from lactase deficiency, impacting digestion.

Involves enzymes like transketolase and transaldolase.
Important for producing sugars that integrate into glycolysis and gluconeogenesis.

Acts as a reducing agent in biosynthesis and detoxification:
- Supports fatty acid, cholesterol, and nucleic acid synthesis.
- Reduces reactive oxygen species (ROS) and aids drug detoxification.
- Generates ROS in immune cells for pathogen destruction.

Regulation occurs by substrate availability and enzyme activity.
Glucose-6-Phosphate Dehydrogenase (G6PD) is the rate-limiting enzyme, activated by NADP+ and inhibited by NADPH.

Long, unbranched polysaccharides made of repeating disaccharides.
Important for extracellular matrix and connective tissues.
Key GAGs include:
- Hyaluronic Acid: Lubricates and provides shock absorption.
- Chondroitin Sulfate: Offers tensile strength to cartilage.
- Heparin: Acts as an anticoagulant.

Glycoproteins with GAGs attached to a core protein, essential for tissue structure and function.
Provide support, modulate cell interactions, and regulate growth factors.

Proteins with oligosaccharide chains, involved in various biological functions:
- Mediate cell recognition and immune responses.
- Integral for hormone and enzyme stability.

The addition of carbohydrate groups to proteins or lipids, categorized into N-linked and O-linked glycosylation based on the attachment location.

Disorders related to GAGs (mucopolysaccharidoses), proteoglycans (Osteoarthritis), and glycoproteins (congenital disorders) can have significant health impacts.

GAGs, proteoglycans, and glycoproteins play roles in metabolic pathways, influencing processes like cell signaling, immune function, and tissue repair.