Unit 2 Test PREP

What are the three postulates of the cell theory?

1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of life. 3. All cells arise from pre-existing cells.

How does the surface-area-to-volume relationship affect cell size?

As a cell grows, its volume increases faster than its surface area, limiting efficient material exchange.

What is a compound microscope?

A light microscope that uses multiple lenses to magnify objects.

What are the benefits and trade-offs of using a compound microscope?

Benefits: Easy to use, allows viewing of live specimens. Trade-offs: Limited magnification and resolution.

What is a transmission electron microscope (TEM)?

Uses electrons to pass through a specimen, producing high-resolution images of internal structures.

What are the benefits and trade-offs of using a transmission electron microscope (TEM)?

Benefits: High magnification and resolution. Trade-offs: Specimens must be dead and prepared in thin slices.

What is a scanning electron microscope (SEM)?

Uses electrons to scan the surface of a specimen, creating a 3D image.

What are the benefits and trade-offs of using a scanning electron microscope (SEM)?

Benefits: High-resolution surface details. Trade-offs: Specimens must be dead, expensive equipment.

What is a confocal microscope?

Uses lasers and fluorescent dyes to produce high-resolution images of thick specimens.

What are the benefits and trade-offs of using a confocal microscope?

Benefits: Allows 3D reconstruction of cells and tissues. Trade-offs: Expensive, requires fluorescent staining.

What is magnification in microscopy?

Increases the apparent size of an object.

What is resolution in microscopy?

The ability to distinguish between two close objects.

What is contrast in microscopy?

The ability to differentiate structures based on color or intensity differences.

How do prokaryotic and eukaryotic cells differ in structure?

Prokaryotic cells: No nucleus, no membrane-bound organelles, smaller size. Eukaryotic cells: Contain a nucleus, membrane-bound organelles, larger size.

What are the components of the prokaryotic cell envelope?

Plasma membrane, cell wall, glycocalyx (capsule or slime layer) providing regulation, structure, and protection.

What are the shapes of prokaryotic cells?

Coccus: Spherical. Bacillus: Rod-shaped. Spirillum: Rigid spiral. Spirochete: Flexible corkscrew.

What are the intracellular components of a prokaryotic cell?

Nucleoid (contains DNA), ribosomes (synthesize proteins), plasmids (small DNA molecules for traits), cytoplasm (site of biochemical reactions).

What is the Endosymbiotic Theory of Cellular Evolution?

Proposes that mitochondria and chloroplasts originated as free-living prokaryotic cells engulfed by eukaryotic cells.

What is the function of the plasma membrane?

Regulates movement of substances into and out of the cell.

What is the function of the cell wall?

Provides structural support and protection in plants, fungi, and prokaryotes.

What is the function of the nucleus?

Stores genetic information (DNA) and controls cellular activities.

What is the function of the nuclear envelope?

Separates the nucleus from the cytoplasm and regulates nuclear transport.

What is the function of the nucleolus?

Produces ribosomal RNA (rRNA) and assembles ribosomes.

What is the function of the rough endoplasmic reticulum?

Synthesizes and processes proteins.

What is the function of the smooth endoplasmic reticulum?

Synthesizes lipids and detoxifies toxins.

What is the function of ribosomes?

Synthesize proteins.

What is the function of mitochondria?

Produce ATP (cellular energy) through aerobic respiration.

What is the function of chloroplasts?

Carry out photosynthesis in plant cells.

What is the function of vacuoles?

Store nutrients, waste, and other materials.

What is the function of the Golgi apparatus?

Modifies, sorts, and packages proteins and lipids for transport.

What is the function of lysosomes?

Break down waste, cellular debris, and foreign substances.

What is the function of flagella?

Provide cell movement.

What is the function of cilia?

Move substances along the cell surface or assist in movement.

What is the function of centrioles?

Help organize cell division in animal cells.

What is the function of microtubules?

Provide structural support and assist in intracellular transport.

What is the function of actin filaments?

Involved in cell shape, movement, and division.

What is the function of intermediate filaments?

Provide mechanical support to the cell.

What is the function of chromosomes?

Carry genetic information in the form of DNA.

What is the function of chromatin?

A complex of DNA and proteins that condenses to form chromosomes.

What is the function of peroxisomes?

Break down fatty acids and detoxify harmful substances.

What is the central dogma of molecular biology?

DNA → RNA → Protein; genetic information flows from DNA to RNA to protein.

Why are some organelles membrane-bound?

Creation of compartments allows for specialized functions and increased efficiency.

How do substances travel through vesicles between organelles?

Vesicles transport materials by budding off from one organelle and fusing with another.

What is the structure of the eukaryotic cell’s plasma membrane?

Phospholipid bilayer forms a semi-permeable barrier; contains proteins, cholesterol, and carbohydrates.

Why is the cell membrane described as a fluid mosaic?

Lipids and proteins can move laterally within the bilayer, creating a diverse mosaic.

Why is the cell membrane described as semi-permeable?

It allows some substances to pass while restricting others based on size, charge, and polarity.

How can you predict the permeability of a substance across the cell membrane?

Highly permeable: Small, nonpolar molecules; Low permeability: Ions.

What are the major types of membrane proteins?

Channel proteins, carrier proteins, receptor proteins, enzymatic proteins, adhesion proteins.

What is the general structure of a signal transduction pathway?

Reception, transduction, and response facilitate cell communication.

How do passive and active transport differ?

Passive transport does not require energy; active transport requires energy (ATP).

What is simple diffusion?

Movement of small, nonpolar molecules across the membrane.

What is facilitated diffusion?

Transport of large or charged molecules via proteins.

What is osmosis?

Movement of water through aquaporins.

What is primary active transport?

Uses ATP directly to move substances against their concentration gradient.

What is secondary active transport?

Uses ion gradients to drive transport of molecules.

What is endocytosis?

Engulfing large molecules into the cell.

What is exocytosis?

Expelling large molecules from the cell.

How does the sodium-potassium pump work?

Pumps 3 Na⁺ out and 2 K⁺ in using ATP.

How does water move across cell membranes?

Water moves by osmosis from low to high solute concentration.

What do hypertonic, hypotonic, and isotonic mean?

Hypertonic: Water leaves cell (shrinking). Hypotonic: Water enters cell (swelling). Isotonic: No net water movement.

How can you predict the outcome of an experiment based on tonicity?

Hypertonic = shrinks, Hypotonic = swells/bursts, Isotonic = stable.

What are the major molecules in the extracellular matrix?

Collagen (strength), elastin (flexibility), proteoglycans (hydration), fibronectin and integrins (cell adhesion).

What are the three major types of cell junctions in animal cells?

Tight junctions, desmosomes, gap junctions; plasmodesmata in plants.

What is energy?

The ability to do work.

How do kinetic and potential energy differ?

Kinetic energy: energy of motion; Potential energy: stored energy.

How do kinetic and potential energy relate to energy flow?

The universe moves toward entropy, converting potential energy to kinetic.

What are the First and Second Laws of Thermodynamics?

First: Energy cannot be created or destroyed. Second: Energy transfer increases entropy.

How do thermodynamics apply to cell chemistry?

First Law: Cells convert chemical energy to ATP. Second Law: Energy lost as heat increases disorder.

How do you read a chemical formula?

Identifies elements and number of atoms (e.g., C₆H₁₂O₆ has 6C, 12H, 6O).

What is free energy (G)?

Energy available to do work; negative ∆G indicates spontaneous reactions.

What are exergonic and endergonic reactions?

Exergonic: Release energy (spontaneous). Endergonic: Require energy input (non-spontaneous).

How do ATP, ADP, and AMP compare in energy?

ATP: Highest energy (3 phosphates), ADP: Medium (2), AMP: Lowest (1).

What is the ATP-ADP cycle?

ATP → ADP + Pi (energy released); ADP + Pi → ATP (energy stored).

What are coupled reactions?

Pairing an exergonic reaction with an endergonic reaction to drive processes.

What is a metabolic pathway?

Series of enzyme-controlled chemical reactions.

What is an enzyme?

A biological catalyst that speeds up chemical reactions.

What is the active site of an enzyme?

The specific region where the substrate binds.

What is the induced fit model?

Enzyme slightly changes shape to better fit substrate.

What factors affect enzyme function?

Temperature, pH, substrate concentration, enzyme concentration, cofactors.

How do inhibitors affect enzyme activity?

Competitive inhibitors block active site; noncompetitive inhibitors change enzyme shape.

What are redox reactions?

Oxidation (loss of electrons) and reduction (gain of electrons) occur together.

What are the chemical formulas for photosynthesis and cellular respiration?

Photosynthesis: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂; Cellular respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP.

How is energy transferred in photosynthesis?

Light energy is converted into chemical energy (glucose).

How is energy transferred in cellular respiration?

Glucose energy is converted into ATP for cellular work.