Biology: Macromolecules, Cell Structure, and Membrane Function

Monomer

The basic building block of a polymer.

Polymer

A large molecule made up of repeating subunits called monomers.

Dehydration reaction

A chemical reaction that involves the loss of a water molecule to form a bond.

Hydrolysis

A chemical reaction that breaks down a compound by adding water.

Carbohydrate

Organic compounds made of carbon, hydrogen, and oxygen, typically in a ratio of 1:2:1.

Glycosidic linkage

A covalent bond formed between two monosaccharides through a dehydration reaction.

Monosaccharide

The simplest form of carbohydrates, consisting of a single sugar unit.

Disaccharide

A carbohydrate composed of two monosaccharides linked by a glycosidic bond.

Polysaccharide

A carbohydrate that consists of a long chain of monosaccharide units.

Starch

A storage polysaccharide in plants, composed of glucose monomers.

Glycogen

A storage polysaccharide in animals, primarily found in liver and muscle cells.

Cellulose

A structural polysaccharide that makes up the cell wall of plants.

Chitin

A structural polysaccharide found in the exoskeleton of arthropods and fungal cell walls.

Lipid

A diverse group of hydrophobic molecules, including fats, oils, and steroids.

Fat

A lipid composed of glycerol and fatty acids, used for energy storage.

Glycerol

A three-carbon alcohol that forms the backbone of triglycerides.

Fatty acid

A long hydrocarbon chain with a carboxyl group at one end, used to form lipids.

Triacylglycerol

A lipid formed from glycerol and three fatty acids; commonly known as fat.

Saturated fatty acid

A fatty acid with no double bonds between carbon atoms, solid at room temperature.

Unsaturated fatty acid

A fatty acid that contains one or more double bonds, liquid at room temperature.

Steroid

A type of lipid characterized by a carbon skeleton with four fused rings.

Cholesterol

A type of steroid that is an essential component of cell membranes.

Protein

A macromolecule composed of amino acids that performs a wide variety of functions in the body.

Conformation

The three-dimensional shape of a protein that is crucial for its function.

Amino acid

The building blocks of proteins, consisting of an amino group, carboxyl group, and side chain.

Polypeptide

A chain of amino acids linked by peptide bonds.

Peptide bond

The covalent bond formed between two amino acids during protein synthesis.

Primary structure

The linear sequence of amino acids in a protein.

Secondary structure

The local folding of a polypeptide chain into structures such as alpha helices and beta sheets.

Alpha helix

A common secondary structure in proteins characterized by a right-handed coil.

Pleated sheet

A common secondary structure in proteins formed by hydrogen bonding between strands.

Tertiary structure

The overall three-dimensional shape of a polypeptide, determined by interactions among side chains.

Hydrophobic interaction

The tendency of nonpolar substances to aggregate in aqueous solutions to minimize contact with water.

Disulfide bridge

A covalent bond formed between the sulfur atoms of two cysteine amino acids, stabilizing protein structure.

Quaternary structure

The structure formed by the assembly of multiple polypeptide chains into a single functional protein.

Denaturation

The process by which a protein loses its native structure and function due to environmental changes.

Nucleotide

The building block of nucleic acids, consisting of a sugar, phosphate group, and nitrogenous base.

Nucleic acid

Biological macromolecules that store and transmit genetic information, including DNA and RNA.

DNA (deoxyribonucleic acid)

The molecule that carries genetic information in cells, composed of two strands forming a double helix.

RNA (ribonucleic acid)

A nucleic acid involved in protein synthesis and gene regulation, usually single-stranded.

Ribose

A five-carbon sugar found in RNA.

Deoxyribose

A five-carbon sugar found in DNA, lacking one oxygen atom compared to ribose.

Polynucleotide

A polymer made up of nucleotide monomers linked together by phosphodiester bonds.

Double helix

The structure formed by two strands of DNA wound around each other.

Prokaryotic cell

A simple, unicellular organism without a nucleus or membrane-bound organelles.

Eukaryotic cell

A complex cell with a nucleus and membrane-bound organelles.

Cytosol

The aqueous component of the cytoplasm in which organelles are suspended.

Plasma membrane

The semi-permeable membrane that surrounds and protects the cell.

Nucleus

The membrane-bound organelle that contains the cell's genetic material.

Nucleoid

The region in prokaryotic cells where the genetic material is located.

Ribosome

The cellular structure responsible for protein synthesis.

Endoplasmic reticulum (ER)

An organelle involved in protein and lipid synthesis; can be rough (with ribosomes) or smooth (without ribosomes).

Rough ER

The portion of the endoplasmic reticulum studded with ribosomes, involved in protein synthesis.

Smooth ER

The portion of the endoplasmic reticulum without ribosomes, involved in lipid synthesis and detoxification.

Glycoprotein

A protein that has carbohydrate groups attached, important for cell recognition and signaling.

Transport vesicle

A membrane-bound sac that transports materials within the cell.

Golgi apparatus

An organelle that modifies, sorts, and packages proteins and lipids for secretion or delivery.

Mitochondria

Organelles known as the powerhouses of the cell, responsible for producing ATP through respiration.

Chloroplast

An organelle found in plant cells that conducts photosynthesis.

Cytoskeleton

A network of fibers that provides structural support and facilitates cell movement.

Extracellular matrix

A network of proteins and carbohydrates outside the cell that provides structural and biochemical support.

Lysosomes

Organelles that contain digestive enzymes to break down waste materials and cellular debris.

Selective permeability

The ability of a membrane to allow certain substances to pass while restricting others.

Amphipathic

Molecules that have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts.

Fluid mosaic model

A model that describes the structure of cell membranes as a mosaic of various proteins floating in or on the fluid lipid bilayer.

Integral proteins

Proteins that are embedded in the lipid bilayer and can span the membrane.

Peripheral proteins

Proteins that are loosely attached to the surface of the membrane and do not penetrate the lipid bilayer.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration.

Concentration gradient

The difference in the concentration of a substance across a space.

Passive transport

The movement of substances across a cell membrane without the use of energy.

Osmosis

The diffusion of water across a selectively permeable membrane.

Transport proteins

Proteins that assist in the movement of substances across a cell membrane.

Aquaporins

Channel proteins that facilitate the rapid transport of water across the cell membrane.

Facilitated diffusion

The process of passive transport of molecules across a membrane via specific transmembrane proteins.

Active transport

The movement of molecules against their concentration gradient, requiring energy.

Sodium-potassium pump

A type of active transport that moves sodium ions out of the cell and potassium ions into the cell.

Endocytosis

The process by which cells take in substances by engulfing them in a vesicle.

Exocytosis

The process by which cells expel materials in vesicles that fuse with the plasma membrane.

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or cells.

Pinocytosis

A type of endocytosis in which a cell engulfs liquid and small particles.

Receptor-mediated endocytosis

A process by which cells internalize molecules based on a recognition system.