Biomolecules and Cell Structure: Study Notes for Anatomy & Physiology

Biomolecules

Introduction to Biomolecules

Biomolecules are organic molecules synthesized by living organisms. They are essential for structure, function, and regulation of the body's tissues and organs. All biomolecules contain carbon, and commonly include elements such as hydrogen, oxygen, and nitrogen.

• Key types: Carbohydrates, proteins, lipids, nucleic acids

• Common features: Carbon-based, synthesized by living organisms

Carbohydrates (C, H, O)

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as a primary energy source and are classified by the number of sugar units.

• General properties: Polar, do not cross membranes easily, function in energy storage and supply

Monosaccharides (1 sugar unit)

• Glucose: Main sugar in blood, primary energy source

• Fructose: Found in fruit

• Galactose: Component of milk sugar

Disaccharides (2 sugar units)

• Sucrose: Table sugar (glucose + fructose)

• Lactose: Milk sugar (glucose + galactose)

Polysaccharides (many sugar units)

• Glycogen: Storage form in animals (liver & muscle); broken down to release glucose

• Starch: Storage form in plants

• Cellulose: Structural component in plants; dietary fiber in humans (not digested or absorbed)

Example: Glycogen is broken down in the liver and muscle to provide glucose during fasting or exercise.

Proteins

Proteins are polymers of amino acids and perform a vast array of functions in the body, including structure, movement, catalysis, transport, and defense.

• Composed of: 20 different amino acids (AAs)

• Essential AAs: Must be obtained from diet

• Non-essential AAs: Synthesized by the body

• Structure: Sequence and folding of amino acids determines function

• Denaturation: Loss of protein shape due to heat, pH, or chemicals, resulting in loss of function

Levels of Protein Structure

• Primary: Sequence of amino acids

• Secondary: Alpha helices and beta sheets (hydrogen bonding)

• Tertiary: 3D folding of a single polypeptide

• Quaternary: Association of multiple polypeptide chains

Types of Proteins

• Peptides: Short chains (<50 AAs); e.g., hormones like insulin

• Proteins: Long chains (>50 AAs); e.g., collagen, keratin, amylase, hemoglobin

Example: Hemoglobin transports oxygen in the blood; amylase catalyzes starch breakdown.

Lipids

Lipids are hydrophobic molecules with many carbon and hydrogen atoms and few oxygen atoms. They function in energy storage, membrane structure, and signaling.

• General properties: Nonpolar, cross membranes easily

Types of Lipids

• Triglycerides: Composed of three fatty acids and one glycerol; main form of stored fat

• Phospholipids: Contain phosphate group and fatty acids; have polar (hydrophilic) and nonpolar (hydrophobic) parts; major component of cell membranes

Example: Phospholipid bilayer forms the structural basis of all cell membranes.

Nucleotides and Nucleic Acids

Nucleotides are the building blocks of nucleic acids, consisting of a sugar, phosphate group, and nitrogenous base. Nucleic acids store and transmit genetic information.

Nucleotides

• Functions: Energy transfer (ATP), cell signaling (second messengers)

• ATP: Main energy currency of the cell; stores energy in phosphate bonds

Nucleic Acids

• DNA (deoxyribonucleic acid): Double helix; stores genetic information; instructions for protein synthesis

• RNA (ribonucleic acid): Single strand; transfers genetic information from DNA to ribosomes for protein synthesis

Example: DNA in the nucleus contains the code for making all proteins in the body.

Biomolecules Practice Comparison Table

This table summarizes the structure, function, and examples of key biomolecules.

Type of Biomolecule	Structure	Function	Examples
Monosaccharide	Single sugar unit	Quick energy source	Glucose, fructose
Disaccharide	Two sugar units	Energy source	Sucrose, lactose
Polysaccharide	Many sugar units	Energy storage, structure	Glycogen, starch, cellulose
Peptide	Short chain of amino acids (<50)	Signaling, regulation	Insulin, glucagon
Protein	Long chain of amino acids (>50)	Structure, enzymes, transport, defense	Collagen, hemoglobin, amylase
Triglyceride	Glycerol + 3 fatty acids	Energy storage	Fats, oils
Phospholipid	Glycerol + 2 fatty acids + phosphate	Cell membrane structure	Phosphatidylcholine
Nucleotide - ATP	Adenine + ribose + 3 phosphates	Energy transfer	ATP
DNA	Double helix of nucleotides	Genetic information storage	Chromosomes
RNA	Single strand of nucleotides	Genetic information transfer	mRNA, tRNA, rRNA

Cell Structure

Plasma Membrane (Cell Membrane)

The plasma membrane is a selectively permeable barrier that surrounds the cell, controlling the movement of substances in and out. It also supports communication, regulation, and cell identification.

• Structure: Phospholipid bilayer with embedded proteins

• Function: Support, communication, regulation, transport, cell identification

Cytoplasm

The cytoplasm consists of all cellular contents between the plasma membrane and the nucleus. It includes cytosol, organelles, and inclusions.

• Cytoskeleton: Network of protein filaments providing support, maintaining shape, holding organelles, and enabling movement and cell division

• Organelles: Specialized structures with specific functions

Nucleus

The nucleus contains the cell's genetic material (DNA) and directs all cellular activities.

• Function: Stores genetic information, controls cell activities

Organelles (Membrane-bound Structures)

• Mitochondrion: Site of ATP synthesis; "powerhouse" of the cell

• Peroxisome: Detoxifies substances, metabolizes fatty acids, synthesizes phospholipids

• Lysosome: Digests damaged organelles and recycles cell components using enzymes

• Ribosome: Synthesizes proteins (can be free or attached to rough ER)

• Rough Endoplasmic Reticulum (RER): Modifies and assembles proteins, attaches sugars, forms parts of plasma membrane

• Smooth Endoplasmic Reticulum (SER): Synthesizes lipids, stores calcium, detoxifies chemicals

Example: Cystic fibrosis is caused by a protein channel defect, leading to thick mucus in the lungs due to improper protein processing in the RER.

Additional info: The notes above expand on the original content by providing definitions, examples, and context for each biomolecule and cell structure, ensuring a comprehensive and self-contained study guide.