Untitled Quiz

Course Information

• Subject/year: Medical Biology/1st year
• Lecturer: Inaam A. Abdulhameed
• Department: Anatomy
• Date: 17/11/2024
• University: University of Mosul
• College: College of Medicine

Lecture Aim

• Understand the structure and functions of molecular components of living organisms.

Intended Learning Outcomes

• Determine the functions of water in living organisms
• Summarize the structure of the pH scale and the importance of buffers to biological systems
• Describe the four major types of biological molecules
• Understand the functions of the four major types of molecules

The Molecular Composition of Cells

• Cells are composed of water, inorganic ions, and organic molecules
• Water is the most abundant molecule in cells, accounting for 70% or more of total cell mass

Functions of Water in the Body

• Water is the primary building block of cells
• Regulates internal body temperature by sweating and respiration
• Carbohydrates and proteins are metabolized and transported in the bloodstream by water
• Assists in flushing waste, mainly through urination
• Acts as a shock absorber for the brain, spinal cord, and fetus
• Forms saliva
• Lubricates joints

Acids and Bases

• Acids dissociate in water, releasing hydrogen ions (H+)
• Hydrochloric acid (HCl) dissociates into H+ and Cl-
• Bases either take up hydrogen ions (H+) or release hydroxide ions (OH-)
• Sodium hydroxide (NaOH) dissociates into Na+ and OH-

pH Scale

• Used to indicate the acidity and basicity of a solution
• Ranges from 0 to 14
• 0 is most acidic, 14 is most basic
• pH 7 is neutral

Buffers

• Resist changes in pH when small amounts of acid or base are added
• Crucial for maintaining stable pH levels in biological systems, essential for proper cellular function and metabolic processes

Inorganic Ions

• Inorganic ions (Na+, K+, Mg2+, Ca2+, HPO42-, Cl-, HCO3-) constitute 1% or less of cell mass
• Involved in various aspects of cell metabolism
• Play critical roles in cell function

Organic Compounds

• In biology, "organic" refers to molecules containing carbon (C) and hydrogen (H) and is associated with living organisms
• Classified into four types: carbohydrates, lipids, proteins, and nucleic acids

1- Carbohydrates

• Almost universally used as an energy source for living organisms
• Some organisms use them for structural function
• Composed of carbon, hydrogen, and oxygen, with a typical hydrogen to oxygen ratio of 2:1
• Subtypes: monosaccharides, disaccharides, and polysaccharides

Monosaccharides

• Simple sugars
• Glucose is the most common, providing immediate energy to the body
• Other common monosaccharides include fructose and galactose

Disaccharides

• Formed by the covalent bonding of two monosaccharides
• Important disaccharides: maltose, sucrose, and lactose

Polysaccharides

• Long chains of monosaccharides linked by covalent bonds
• Examples: starch, glycogen, and cellulose
• Starch is the stored form of sugars in plants
• Glycogen is the stored form of glucose in the human liver

2- Lipids

• Diverse in structure and function
• Do not dissolve in water
• Composed mostly of carbon and hydrogen atoms
• Functions: energy storage, hormone components, and cellular membrane constituents
• Types: fats, oils, waxes, phospholipids, and steroids

Fats and Oils (Triglycerides)

• Formed when glycerol reacts with three fatty acid molecules
• A fatty acid is a carbon-hydrogen chain ending with an acidic group (COOH)
• Fatty acids categorized as saturated or unsaturated based on the presence of double bonds

Saturated Fatty Acids

• Have no double bonds between carbon atoms
• Solid at room temperature

Unsaturated Fatty Acids

• Have double bonds between carbon atoms
• Liquid at room temperature

Phospholipids

• Similar to fats, but the third fatty acid is replaced by a phosphate group
• Hydrophilic ("water-loving") phosphate end and hydrophobic ("water-fearing") fatty acid end
• Major components of cell membranes

Steroids

• Lipids with a unique structure of four fused carbon rings
• Cholesterol is a major steroid, a component of animal plasma membranes
• Precursor to other steroids, including sex hormones

3- Proteins

• Macromolecules with amino acid subunits
• Primary structure: a sequence of amino acids linked together; a chain
• Secondary structure: the chain twists or folds
• Tertiary structure: the final 3D shape of the protein
• Quaternary structure: how multiple polypeptide chains interact

Protein Functions

• Support (e.g., keratin in hair and nails, collagen in tissues)
• Enzymes (catalyzing biochemical reactions)
• Transport (e.g., hemoglobin in blood)
• Defense (e.g., antibodies)
• Hormones (e.g., Insulin regulating blood sugar)
• Motion (e.g., actin and myosin in muscle contraction)

4- Nucleic Acids

• Key macromolecules for the continuity of life
• Carry genetic blueprints and instructions for cell functioning
• Two main types: DNA and RNA
• Composed of monomers called nucleotides
• Nucleotides have three components: a nitrogenous base, a pentose sugar, and a phosphate group
• DNA is double-stranded, forming a double helix
• RNA is single-stranded

Nucleic Acids in DNA and RNA

• Nucleotides in DNA contain deoxyribose sugar; in RNA, ribose sugar
• DNA bases: adenine (A), thymine (T), guanine (G), and cytosine (C)
• RNA bases: adenine (A), uracil (U), guanine (G), and cytosine (C)

Summary of Lecture

• Water is the most abundant molecule in organisms, essential for many functions
• pH reflects acidity/basicity
• Buffers regulate pH
• Carbohydrates, lipids, proteins, and nucleic acids are important organic molecules with specific roles in cells

Quiz Questions

• An example of a polysaccharide used for energy storage in humans is glycogen
• Saturated and unsaturated fatty acids differ in the number of carbon-to-carbon double bonds