Chapters 5, 6, and 7 Biology Review: Macromolecules, The Cell, and Membrane Transport

Comprehensive flashcards covering key vocabulary, organelle structures, biochemical properties, and transport mechanisms from lecture chapters 5, 6, and 7.

Macromolecule

A large molecule built from smaller subunits, belonging to one of $4$ classes: carbohydrates, lipids, proteins, or nucleic acids.

Polymer

A long chain of repeating monomers, such as sugars in carbohydrates, amino acids in proteins, or nucleotides in nucleic acids.

Lipids

The only class of macromolecules that is not a true polymer because they lack repeating monomers; they are hydrophobic and insoluble in water.

Monosaccharide

A single sugar unit that serves as a monomer for complex carbohydrates, including glucose, fructose, galactose, ribose, and deoxyribose.

Disaccharide

A double sugar constructed from two monosaccharides joined by a dehydration reaction, such as sucrose, lactose, or maltose.

Sucrose

A disaccharide known as table sugar, formed from glucose and fructose, commonly found in plants.

Lactose

A disaccharide found in milk, composed of glucose and galactose.

Maltose

A disaccharide made of two glucose molecules, found in germinating seeds and malt.

Starch

A plant energy storage polysaccharide made of $\alpha$-glucose monomers with a helical/coiled structure that humans can digest using amylase.

Glycogen

A glucose polymer used for short-term energy storage in animals, primarily stored in the liver and muscle tissue.

Cellulose

A structural polysaccharide found in plant cell walls made of $\beta$-glucose; forms straight chains grouped into bundles (microfibrils) by hydrogen bonds and is indigestible to humans (insoluble fiber).

Chitin

A structural carbohydrate found in fungal cell walls and arthropod exoskeletons whose glucose units carry a nitrogen-containing group (N-acetylglucosamine).

Dehydration Synthesis

An anabolic, energy-requiring reaction that joins monomers into polymers by removing a molecule of $H_2O$.

Hydrolysis

A catabolic reaction used in digestion that breaks down polymers into monomers by adding a molecule of $H_2O$, releasing energy.

Glycosidic Linkage

The covalent bond formed between two monosaccharides by a dehydration reaction in carbohydrates.

Ester Linkage

The covalent bond formed between a glycerol molecule and fatty acid chains in lipids (fats).

Peptide Bond

The covalent bond linking the carboxyl carbon of one amino acid to the amino nitrogen of the next amino acid in a polypeptide chain.

Phosphodiester Linkage

The covalent bond that links adjacent nucleotides together in nucleic acids.

Fats (Triglycerides)

Lipids composed of glycerol bonded to $3$ fatty acids via ester bonds, functioning in energy storage, insulation, and cushioning.

Phospholipids

Amphipathic lipids consisting of glycerol, $2$ fatty acids, and a phosphate head, forming the cell membrane bilayer.

Steroids

Lipids characterized by a carbon skeleton of $4$ fused carbon rings, including cholesterol and steroid hormones (estrogen, testosterone).

Saturated Fatty Acids

Fatty acids with no $C=C$ double bonds and the maximum number of hydrogen atoms; they possess straight tails that pack tightly, remaining solid at room temperature.

Unsaturated Fatty Acids

Fatty acids containing one or more $C=C$ double bonds with fewer hydrogen atoms; their kinked tails prevent tight packing, keeping them liquid at room temperature.

N-terminus

The start of a polypeptide chain possessing a free amino group ($-NH_2$).

C-terminus

The end of a polypeptide chain possessing a free carboxyl group ($-COOH$).

Primary Protein Structure

The specific linear sequence of amino acids in a polypeptide chain held together by covalent peptide bonds.

Secondary Protein Structure

Localized coils ($\alpha$ helix) and folds ($\beta$ pleated sheet) in a polypeptide resulting from hydrogen bonds between backbone atoms ($C=O$ and $N-H$).

Tertiary Protein Structure

The overall three-dimensional shape of a polypeptide formed by interactions between R groups, including hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals forces, and disulfide bridges.

Purines

Double-ring nitrogenous bases comprising adenine (A) and guanine (G).

Pyrimidines

Single-ring nitrogenous bases comprising cytosine (C), thymine (T, in DNA only), and uracil (U, in RNA only).

Nucleotide

The monomer of nucleic acids composed of a $5$-carbon (pentose) sugar, a phosphate group, and a nitrogenous base.

Nucleoside

A molecular subunit consisting only of a $5$-carbon (pentose) sugar and a nitrogenous base, lacking a phosphate group.

Endomembrane System

A network of eukaryotic membranes connected directly or via vesicles, consisting of the nuclear envelope, rough ER, smooth ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

Free Ribosomes

Ribosomes suspended in the cytosol that synthesize proteins primarily utilized within the cell, such as metabolic enzymes.

Bound Ribosomes

Ribosomes attached to the rough endoplasmic reticulum that produce proteins destined for membranes, lysosomes, or export from the cell.

Smooth Endoplasmic Reticulum

An endomembrane organelle devoid of ribosomes that performs lipid and steroid synthesis, carbohydrate metabolism, poison detoxification, and $Ca^{2+}$ storage.

Golgi Apparatus

An organelle with cis and trans faces that functions like a post office by modifying, sorting, packaging, and shipping cellular products.

Lysosome

A digestive organelle filled with hydrolytic enzymes that breaks down macromolecules and recycles intracellular organelles via autophagy.

Peroxisome

A metabolic compartment that breaks down fatty acids, produces hydrogen peroxide ($H_2O_2$), and subsequently converts it into water using catalase.

Endosymbiont Theory

The theory that mitochondria and chloroplasts originated as engulfed prokaryotes, supported by their circular DNA, their own ribosomes, double membranes, and binary fission division.

Chromatin

The complex of DNA and protein molecules (histones) that constitutes chromosomes, remaining loose and uncoiled in non-dividing cells.

Gap Junctions

Intercellular channels connecting adjacent animal cells that allow the direct passage of ions, small molecules, and communication signals.

Plasmodesmata

Channels through plant cell walls that link the cytoplasm of neighboring cells, allowing transport of water, solutes, and signals.

Tight Junctions

Intercellular junctions that fuse the membranes of adjacent animal cells together to form a leak-proof barrier, preventing fluid from passing between cells.

Desmosomes

Anchoring junctions fastened by intermediate filaments that staple or rivet animal cells together in tissues under high mechanical stress.

Microtubules

The thickest cytoskeletal fibers made of tubulin, which maintain cell shape, serve as tracks for organelle movement, and form spindle fibers, cilia, flagella, and centrioles.

Microfilaments

The thinnest cytoskeletal fibers composed of actin, functioning in cell shape, muscle contraction (with myosin), cytokinesis, pseudopodia, and cytoplasmic streaming.

Intermediate Filaments

Permanent structural cytoskeletal fibers composed of keratins (and others) that bear tension and anchor organelles like the nucleus.

Nuclear Lamina

A network of intermediate filaments (lamins) lining the inside of the nuclear envelope that supports nuclear shape and anchors chromatin.

Fluid Mosaic Model

The structural model of the plasma membrane, describing it as a fluid phospholipid bilayer embedded with a mosaic of drifting proteins, cholesterol, and carbohydrates.

Integral Membrane Proteins

Amphipathic proteins embedded in or spanning the phospholipid bilayer, with hydrophobic regions contacting fatty acid tails and hydrophilic portions exposed to water.

Peripheral Membrane Proteins

Hydrophilic proteins loosely attached to the exterior or interior surface of the membrane or to integral proteins, without entering the hydrophobic core.

Passive Transport

The movement of substances across a biological membrane down their concentration gradient without requiring cellular energy ($\text{ATP}$).

Osmosis

The diffusion of water across a selectively permeable membrane from an area of lower solute concentration (higher free water) to higher solute concentration.

Facilitated Diffusion

Passive transport of substances across a membrane down their concentration gradient through specific channel or carrier proteins without cellular energy expenditure.

Active Transport

The energy-requiring ($\text{ATP}$) movement of solutes across a membrane against their concentration gradient (low to high) mediated by specific carrier transport proteins.

Sodium-Potassium Pump

An electrogenic active transport pump that hydrolyzes $\text{ATP}$ to pump $3\,Na^+$ out of the cell and $2\,K^+$ into the cell against their gradients.

Phagocytosis

A type of endocytosis ('cell eating') in which a cell engulfs large particles or whole cells using pseudopodia, packaging them into a food vacuole.

Pinocytosis

A non-specific form of endocytosis ('cell drinking') where the cell takes in droplets of extracellular fluid and dissolved solutes in tiny vesicles.

Receptor-Mediated Endocytosis

A highly specific endocytic process wherein extracellular ligands bind to specific receptors in coated pits, triggering vesicle formation.

Hypotonic Solution

A surrounding environment with a lower solute concentration than the cytoplasm, causing water to enter the cell; animal cells swell and may lyse, while plant cells become turgid.

Hypertonic Solution

A surrounding environment with a higher solute concentration than the cytoplasm, causing water to leave the cell; animal cells shrivel and plant cells undergo plasmolysis.

Isotonic Solution

A surrounding environment with a solute concentration equal to that of the cell, resulting in no net movement of water; normal for animal cells, but causes plant cells to become flaccid.

Turgor Pressure

The pressure exerted by the fluid-filled central vacuole pushing the plasma membrane firmly against the cell wall in plant cells.

Membrane Potential

The electrical charge difference (voltage) across a cell's plasma membrane, where the inside of the cell is negative relative to the outside.

Electrochemical Gradient

The combination of a chemical concentration gradient and an electrical force that drives the passive movement of ions across a membrane.