Unit 2 Bio Expanded

What are the three premises of cell theory?

1. All living organisms are composed of one or more cells. 2. The cell is the basic unit of structure and organization in all living things. 3. All cells arise only from pre

How does light microscopy differ from electron microscopy?

Light microscopes use visible light to magnify specimens up to about 1000x, allowing observation of living cells in color. Electron microscopes use beams of electrons, providing much higher resolution (up to 1,000,000x), but can only view nonliving, fixed samples coated with metal.

What are the two main types of electron microscopy?

Transmission Electron Microscopy (TEM) passes electrons through thin sections to view internal cell structures. Scanning Electron Microscopy (SEM) bounces electrons off the surface to create 3D images of cell exteriors.

What are the key differences between prokaryotic and eukaryotic cells?

Prokaryotes (bacteria and archaea) lack a true nucleus and membrane

What external structures are found on bacterial cells?

Flagella (used for motility), pili (transfer DNA during conjugation), fimbriae (attachment to surfaces), and capsules (sticky protective layer preventing desiccation and aiding immune evasion).

Why is cellular compartmentalization important?

It allows for specialized environments within the cell, increasing efficiency by isolating incompatible reactions, localizing enzymes, and organizing metabolic pathways in organelles like mitochondria, ER, and Golgi.

What is cytosol and its function?

Cytosol is the semi

Compare catabolism and anabolism.

Catabolism breaks down large molecules (e.g., glucose) into smaller ones, releasing energy (exergonic). Anabolism uses that energy to build complex molecules (e.g., proteins, lipids) from smaller subunits (endergonic).

What organelle carries out translation in the cytosol?

Ribosomes, composed of rRNA and proteins, carry out translation by reading mRNA and assembling amino acids into polypeptides with the help of tRNA and translation factors.

What are the three components of the cytoskeleton?

Microtubules (made of tubulin; maintain shape, aid vesicle transport, form cilia/flagella), Intermediate filaments (made of keratin

What are the functions of the Rough ER and Smooth ER?

Rough ER (studded with ribosomes) synthesizes and folds proteins, which are often sent to the Golgi or cell membrane. Smooth ER synthesizes lipids, steroids, detoxifies chemicals, and stores calcium ions (especially in muscle cells).

What is the purpose of the Golgi apparatus?

It modifies, sorts, and packages proteins and lipids from the ER into vesicles for transport. It also produces lysosomes and secretory vesicles and tags proteins with molecular “addresses.”

What is the function of lysosomes?

Lysosomes digest macromolecules, old organelles, and pathogens using hydrolytic enzymes like proteases and lipases. They maintain an acidic pH (around 4.5) through proton pumps for enzyme activity.

What are mitochondria and their functions?

Mitochondria perform cellular respiration by converting glucose and oxygen into ATP. They have a double membrane, their own DNA and ribosomes, and can replicate independently. The inner membrane folds (cristae) increase surface area for ATP production.

Where do transcription and translation occur?

Transcription occurs in the nucleus, where DNA is used to create mRNA. Translation occurs in the cytoplasm on ribosomes (free or attached to the Rough ER) to form proteins.

What are chloroplasts and their function?

Found in plant and algae cells, chloroplasts perform photosynthesis using sunlight to convert CO₂ and H₂O into glucose. They contain thylakoids (with chlorophyll), grana (stacks), and stroma (fluid interior).

What are peroxisomes and their function?

Peroxisomes break down fatty acids, detoxify harmful substances, and generate hydrogen peroxide (H₂O₂), which is converted into water and oxygen by catalase enzymes.

What is the plasma membrane made of?

A phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. It regulates transport, maintains homeostasis, and enables communication and recognition.

What is an amphipathic molecule?

A molecule with both hydrophobic (nonpolar) and hydrophilic (polar) regions. Example: phospholipids, which form the bilayer with hydrophilic heads facing water and hydrophobic tails inside.

What are the three types of membrane proteins?

Integral (span the bilayer and act as channels), Peripheral (attached to the surface for signaling), and Lipid

What are the forms of diffusion?

Simple diffusion moves small, nonpolar molecules directly across the membrane; facilitated diffusion requires transport proteins to move polar or charged molecules down their concentration gradient.

What are the three forms of tonicity?

Isotonic: equal solute concentration, no net water movement. Hypertonic: higher solute outside, cell shrinks. Hypotonic: lower solute outside, cell swells. Cells maintain balance via osmoregulation.

What is active transport?

The movement of molecules against their gradient using energy. Primary active transport uses ATP (e.g., Na⁺/K⁺ pump), while secondary uses ion gradients to drive co

What is endocytosis and its types?

The process of taking materials into the cell via vesicles. Types: Phagocytosis (cell eating of large particles), Pinocytosis (cell drinking of fluids), and Receptor

What is exocytosis?

The process where vesicles fuse with the plasma membrane to release materials like hormones, neurotransmitters, or waste outside the cell.

What are the five forms of cell

to

What are ligands and why are they important?

Ligands are signaling molecules that bind to receptors, triggering a response such as enzyme activation or gene expression. Examples: hormones, neurotransmitters.

What are the main types of cell receptors?

G

What are intracellular receptors?

Receptors located inside the cytoplasm or nucleus that bind hydrophobic ligands (e.g., steroid hormones) which can cross the membrane to regulate gene expression directly.

What is apoptosis?

Programmed cell death involving controlled dismantling of cellular components. It removes damaged, infected, or unnecessary cells without causing inflammation.

What are anchoring junctions?

Structures that attach cells to each other or to the extracellular matrix. Types include adherens junctions (cadherins + actin), desmosomes (intermediate filaments), hemidesmosomes (connect to basal lamina), and focal adhesions (integrins + actin).

What are tight junctions?

Sealing junctions between cells that prevent leakage of substances across epithelial layers, creating distinct apical and basal surfaces.

What are gap junctions?

Protein channels (connexons) connecting adjacent animal cells, allowing passage of ions and small molecules for cell signaling and coordination.

What is the middle lamella?

A pectin

What are plasmodesmata?

Channels that pass through plant cell walls, connecting the cytoplasm of adjacent cells to allow the exchange of water, ions, and signaling molecules.