Biochemistry 2 Study Notes

Definition of Metabolism: The sum of all chemical reactions in the body that maintain cellular activities.
Metabolic Pathways: A series of interconnected biochemical reactions that create a complex network of metabolism.
- Metabolic Map: A visual representation of metabolic pathways, highlighting the connections between them and the intermediates involved.
- Catabolism: The breakdown of larger molecules into smaller units, releasing energy.
- Anabolism: The synthesis of larger molecules from smaller units, requiring energy.

Discussion of the processes involved in nitrogen fixation, amino acid metabolism, and the urea cycle.

Involves the metabolism of glucose and other sugars.
- Glycolysis: The metabolic pathway that converts glucose into pyruvate, yielding a net gain of ATP.
- Pathways for carbohydrate metabolism include gluconeogenesis and the citric acid cycle.

Bioenergetics: The study of energy flow through living systems.
Oxidative Phosphorylation: The process by which ATP is formed from the transfer of electrons through the electron transport chain (ETC).
- Involves the oxidation of NADH and FADH2 and the reduction of oxygen to water.
- ATP is produced via the chemiosmotic gradient created by proton pumping across the mitochondrial membrane.

Involves metabolism of fatty acids and triglycerides.
- Beta-Oxidation: The breakdown of fatty acids to acetyl-CoA, which can then enter the citric acid cycle.
- Lipid synthesis: The generation of fatty acids and storage of energy.

The interaction and regulatory mechanisms between catabolic and anabolic pathways to maintain homeostasis.

Metabolic pathways must be coordinated. Involves:
- Signals from within the cell (Intracellular): Regulatory signals influence metabolic pathways.
- Communication between cells: Hormones and neurotransmitters provide long-range integration of metabolism.

Definition: The process by which cells respond to chemical signals through various pathways.
Types of Signal Transduction:
- Transduction by Intracellular Receptors: Ligands (e.g., steroid hormones) pass through the cell membrane and bind to receptors inside the cell, affecting gene expression.
- Transduction by Cell-Surface Receptors: Involves the binding of signaling molecules → (ligands) to cell surface receptors, initiating a cellular response through secondary messengers.
- Ligand-Gated Ion Channels: Regulate ion flow across membranes in response to ligands, important in neurotransmission.
- Receptor Enzyme: They have intrinsic enzymatic activity (e.g., insulin receptor).
- Receptors Using Second Messenger Systems: Include adenylate cyclase, phosphatidylinositol system, and others.

Enzymes: Biological catalysts that speed up reactions. Enzymatic activity is not isolated but occurs in specific sequenced pathways.
- Pathways: A series of enzymatic reactions leading from substrate to product. Example of reactions illustrated between enzymes that connect various metabolites.

Catabolism:
- Breaking down larger molecules, generating energy stored as ATP.
- Examples: Degradation of polysaccharides and proteins to CO2, NH3, and H2O.
Anabolism:
- Building complex molecules from simple precursors, requiring energy input.
- Examples: Synthesis of proteins from amino acids.

Energy liberation occurs through electron transfer from NADH and FADH2 to O2 through the electron transport chain.

Stage 1: Production of Acetyl-CoA from glycolysis and pyruvate.
Stage 2: Oxidation of Acetyl-CoA in the citric acid cycle.
Stage 3: Electron transfer and oxidative phosphorylation leading to ATP formation.

Intracellular Receptors: Ligands trigger responses by entering the nucleus, binding to DNA, and influencing gene expression.
Cell-Surface Receptors: Activate intracellular signaling pathways upon ligand binding, leading to rapid cellular responses.
Classes of Cell-Surface Receptors:
- Ligand-gated ion channels (e.g., neurotransmitter receptors).
- Receptor enzymes (e.g., catalytic receptors).
- Second messenger systems (e.g., α- and β-adrenergic receptors).

Describes the GPCR signaling cascade, Involvement of G-proteins in the activation of downstream effectors like adenylate cyclase which converts ATP to cAMP (a second messenger).
- G-protein Inactivation: Is achieved through GTP hydrolysis.

Involves the hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C, leading to the generation of second messengers inositol trisphosphate (IP3) and diacylglycerol, which subsequently influence calcium release and protein activation in cells.

Role: Triggers a variety of cellular responses, including muscle contraction and neurotransmitter release.
- Calmodulin: A calcium-binding protein that modulates various enzyme activities in response to calcium levels.

Includes cyclic GMP (cGMP) and nitric oxide signaling pathways, which influence various physiological processes such as vascular relaxation and neurotransmission.