General Biology: Biomolecules, Cell Structure, and Membrane Transport Study Guide

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Monosaccharides are the simplest carbohydrates, serving as building blocks for more complex sugars.

Definition: Monosaccharides are single sugar molecules, such as glucose, fructose, and galactose.
Triose: A monosaccharide with three carbon atoms (e.g., glyceraldehyde).
Alpha and Beta Glucose: These refer to different anomeric forms of glucose, distinguished by the position of the hydroxyl group on carbon 1.
Aldose vs. Ketose: Aldoses have an aldehyde group (e.g., glucose), while ketoses have a ketone group (e.g., fructose).
Example: Glucose (an aldose) and fructose (a ketose) are both hexoses but differ in their functional groups.

Polysaccharides are long chains of monosaccharide units linked by glycosidic bonds, with diverse biological roles.

Types: Starch, glycogen, cellulose, and chitin are common polysaccharides.
Linkages: The type of glycosidic linkage (e.g., α(1→4), β(1→4)) determines the structure and function.
Structural vs. Storage: Cellulose (structural in plants) vs. starch/glycogen (energy storage).
Chemical Evaluation: Polysaccharides can be analyzed for their monosaccharide composition and linkage types.
Example: Starch is composed of α-glucose units, while cellulose is made of β-glucose units.

Lipids are hydrophobic biomolecules essential for energy storage, membrane structure, and signaling.

Types: Triglycerides, phospholipids, and steroids.
Phospholipids: Major component of cell membranes; consist of a hydrophilic head and hydrophobic tails.
Saturated vs. Unsaturated: Saturated fatty acids have no double bonds; unsaturated have one or more double bonds.
Energy Storage: Fats store energy efficiently due to their high caloric content.
Example: Triglycerides are formed by esterification of glycerol with three fatty acids.

Cells are classified as prokaryotic or eukaryotic based on their internal organization.

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; DNA is stored in the nucleoid region.
Eukaryotic Cells: Have a nucleus and various organelles (e.g., mitochondria, ER, Golgi apparatus).
Plant Cells: Contain chloroplasts, cell walls, and large central vacuoles.
Example: Escherichia coli is a prokaryote; Arabidopsis thaliana is a eukaryotic plant.

Organelles perform specialized functions within eukaryotic cells.

Ribosomes: Synthesize proteins.
Rough ER: Studded with ribosomes; involved in protein synthesis and processing.
Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.
Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
Lysosomes: Contain digestive enzymes for breaking down macromolecules.
Chloroplasts: Site of photosynthesis in plant cells; contain thylakoids and stroma.
Bacterial DNA Storage: In prokaryotes, DNA is stored in the nucleoid region.
Example: The Golgi apparatus packages proteins for secretion.

The plasma membrane is a selectively permeable barrier composed mainly of phospholipids.

Phospholipid: Consists of a glycerol backbone, two fatty acid tails, and a phosphate group.
Regions: Hydrophilic (polar) head and hydrophobic (nonpolar) tails.
Membrane Fluidity: Influenced by fatty acid saturation and cholesterol content.
Example: Unsaturated fatty acids increase membrane fluidity.

Substances move across cell membranes via various transport mechanisms.

Passive Transport: Includes diffusion and osmosis; does not require energy.
Active Transport: Requires energy to move substances against their concentration gradient.
Osmosis: Movement of water across a semipermeable membrane.
Hypertonic, Hypotonic, Isotonic: Terms describing relative solute concentrations.
Diffusion: Movement of molecules from high to low concentration.
Example: Sodium-potassium pump uses ATP to transport ions against their gradients.

Macromolecules can be identified based on their structure and function.

Types: Carbohydrates, lipids, proteins, nucleic acids.
Identification: Based on functional groups, monomer units, and biological roles.
Example: Proteins are identified by the presence of amino acids and peptide bonds.

Transport Type	Energy Required	Direction	Example
Simple Diffusion	No	Down gradient	O2, CO2
Facilitated Diffusion	No	Down gradient	Glucose via GLUT transporter
Osmosis	No	Water down gradient	Water through aquaporins
Active Transport	Yes (ATP)	Against gradient	Sodium-potassium pump

Understanding these topics is essential for success in General Biology. Focus on definitions, mechanisms, and applications.