Biomolecules and Cellular Respiration: Study Notes for Anatomy & Physiology

CARBOHYDRATES

Overview of Carbohydrates

Carbohydrates are sugars, starches, and related compounds that serve as a primary energy source and structural components in cells.

• Energy Source: Sugars and starches provide 4 Cal/g; grains are about 55% carbohydrate.

• Structural Roles: Found in membrane proteins, receptors, and dietary fiber.

• General Formula: Carbohydrates have the formula (CH2O)n.

Monosaccharides

Monosaccharides are single carbohydrate monomers, commonly referred to as "simple sugars."

• Examples: Glucose, Dextrose, Galactose, Fructose

• Hexoses: Six-carbon sugars such as Glucose and Pentose (five-carbon sugars)

• Function: Serve as building blocks for larger carbohydrates and are rapidly absorbed into the bloodstream.

• High Glycemic Index: Indicates rapid increase in blood sugar after consumption.

Disaccharides

Disaccharides consist of two monosaccharides joined by a glycosidic bond.

• Maltose: Glucose-glucose

• Sucrose: Glucose-fructose (table sugar)

• Lactose: Glucose-galactose (milk sugar)

• Formation: Created via dehydration synthesis and broken down by hydrolysis.

Polysaccharides

Polysaccharides are long chains of monosaccharides, serving as energy storage and structural molecules.

• Glycogen: Highly branched glucose polymer; main storage form in animals.

• Starch: Storage form in plants; energy source for humans.

• Cellulose: Structural component in plants; humans cannot digest but provides dietary fiber.

Comparison Table: Major Carbohydrates

Type	Monomer	Function
Monosaccharide	Glucose	Quick energy
Disaccharide	Sucrose	Transported sugar
Polysaccharide	Glycogen	Energy storage
Polysaccharide	Cellulose	Structural support

LIPIDS

Overview of Lipids

Lipids are hydrophobic organic molecules, including fats, oils, and steroids, that serve as energy storage, structural components, and signaling molecules.

• High Energy Content: 9 Cal/g

• Fatty Acids: Long hydrocarbon chains with a terminal carboxylic acid group

• Amphipathic Nature: Some lipids have both hydrophilic and hydrophobic regions

Types of Fatty Acids

• Saturated Fatty Acids: No double bonds; solid at room temperature; associated with atherosclerosis

• Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature; healthier for cardiovascular system

• Trans Fats: Artificially produced; increase LDL cholesterol

Major Classes of Lipids

• Triglycerides (Neutral Fats): Three fatty acids bonded to glycerol; main energy storage form

• Phospholipids: Form cell membranes; amphipathic

• Eicosanoids: Derived from arachidonic acid; include prostaglandins, thromboxanes, leukotrienes

• Steroids: Four-ring structure; includes cholesterol, hormones

Comparison Table: Major Lipid Classes

Class	Structure	Function
Triglyceride	Glycerol + 3 fatty acids	Energy storage
Phospholipid	Glycerol + 2 fatty acids + phosphate	Membrane structure
Steroid	Four fused rings	Hormones, membrane fluidity
Eicosanoid	20-carbon fatty acid derivatives	Signaling, inflammation

NUCLEIC ACIDS

Overview of Nucleic Acids

Nucleic acids are polymers of nucleotides that store and transmit genetic information and participate in cellular energy transfer.

• Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

• Nucleotide Structure: Nitrogenous base, pentose sugar, phosphate group

• Functions: Genetic material, energy molecules (ATP), signaling

DNA vs. RNA

• DNA: Double-stranded, stores genetic information

• RNA: Single-stranded, involved in protein synthesis and regulation

Comparison Table: DNA vs. RNA

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Strands	Double	Single
Bases	A, T, G, C	A, U, G, C
Function	Genetic storage	Protein synthesis

PROTEINS

Overview of Proteins

Proteins are polymers of amino acids that perform a wide variety of structural, enzymatic, and regulatory functions in the body.

• Structure: Composed of C, H, O, N, S

• Types: Globular (soluble) and fibrous (insoluble)

• Functions: Enzymes, structural support, transport, signaling, immune defense

Levels of Protein Structure

• Primary: Sequence of amino acids

• Secondary: Alpha helix or beta sheet folding

• Tertiary: Overall 3D shape

• Quaternary: Multiple polypeptide chains

Protein Structure Table

Level	Description
Primary	Amino acid sequence
Secondary	Alpha helix, beta sheet
Tertiary	3D folding
Quaternary	Multiple chains

Protein Bonds and Stability

• Ionic Bonds: Between charged R-groups

• Hydrogen Bonds: Between polar R-groups

• Hydrophobic Interactions: Between non-polar R-groups

• Disulfide Bridges: Covalent bonds between cysteine residues

Denaturation

• Causes: Acid, heat, chemical perturbation

• Effect: Loss of protein structure and function

ENZYMES

Overview of Enzymes

Enzymes are biological catalysts that accelerate chemical reactions by lowering activation energy.

• Specificity: Each enzyme acts on a specific substrate

• Active Site: Region where substrate binds

• Enzyme-Substrate Complex: Temporary association during reaction

• Regulation: Competitive and non-competitive inhibitors, allosteric sites

• Temperature and pH: Affect enzyme activity; each enzyme has an optimum

Enzyme Reaction Equation

$E + S \rightarrow ES \rightarrow E + P$

Where E = enzyme, S = substrate, ES = enzyme-substrate complex, P = product.

METABOLIC PATHWAYS & CELLULAR RESPIRATION

Overview of Metabolic Pathways

Metabolic pathways are series of chemical reactions that convert molecules for energy production, biosynthesis, and cellular maintenance.

• Anabolic Pathways: Build complex molecules; require energy

• Catabolic Pathways: Break down molecules; release energy

• Intermediary Metabolism: Pathways are interconnected

Cellular Respiration

Cellular respiration is the process by which cells extract energy from nutrients to produce ATP.

• Anaerobic Respiration: Occurs without oxygen; produces 2 ATP and lactic acid or ethanol

• Aerobic Respiration: Requires oxygen; produces 30-32 ATP per glucose

• Major Pathways: Glycolysis, Krebs Cycle (Citric Acid Cycle), Electron Transport Chain

ATP Cycle Equation

$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

ATP is hydrolyzed to ADP and inorganic phosphate, releasing energy for cellular processes.

Summary Table: Cellular Respiration Pathways

Pathway	Location	ATP Yield
Glycolysis	Cytoplasm	2 ATP
Krebs Cycle	Mitochondria	2 ATP
Electron Transport Chain	Mitochondria	26-28 ATP

Additional info: Some explanations and tables have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.