Lecture 3 - The Cellular Level of Organization (Test Prep)

What is the cell?

The basic unit of structure and function in the body.

What does it mean when a cell is “differentiated”?

It has developed specialized structures and functions.

What are the three main parts of a composite cell?

Nucleus, Cytoplasm, and Cell (Plasma) Membrane.

What is the primary function of the cell (plasma) membrane?

It maintains cell integrity and regulates entry and exit of substances.

What does “selectively permeable” mean?

Allows some substances to pass while blocking others.

What is signal transduction?

Process by which the cell receives and responds to external messages.

What is the structure of the plasma membrane?

Phospholipid bilayer with proteins and carbohydrates (fluid mosaic model).

Describe the structure of phospholipids.

Hydrophilic heads (water-loving) and hydrophobic tails (water-fearing).

What is the role of cholesterol in the membrane?

Stabilizes the membrane and makes it less permeable to water-soluble substances.

What are integral and peripheral proteins?

Integral: Penetrate the membrane.

Peripheral: Attached to one surface of the membrane.

List some membrane protein functions.

Channels, receptors, enzymes, cell identity markers, and adhesion molecules.

What is the glycocalyx and its functions?

A carbohydrate coating on the cell surface; functions include protection, cell recognition, adhesion, immunity, and fertilization.

What is cytoplasm composed of?

Cytosol (fluid) and organelles (structures with specific functions).

What is the function of the cytoskeleton?

Provides structure and movement through protein rods and tubules.

Function of ribosomes?

Site of protein synthesis.

Function of rough endoplasmic reticulum (RER)?

Contains ribosomes; synthesizes and transports proteins.

Function of smooth endoplasmic reticulum (SER)?

Synthesizes lipids and detoxifies substances.

Function of the Golgi apparatus?

Modifies, packages, and ships proteins and lipids.

Function of vesicles?

Store or transport substances within the cell.

Function of mitochondria?

Produce ATP via cellular respiration (“powerhouse of the cell”).

Function of lysosomes?

Contain digestive enzymes to break down old cell parts and waste.

Function of peroxisomes?

Break down lipids, alcohol, and hydrogen peroxide.

What are microfilaments, microtubules, and intermediate filaments?

Microfilaments: Thin actin rods for movement (e.g., muscle contraction).

Microtubules: Tubulin tubes for shape, transport, and cilia/flagella.

Intermediate filaments: Provide strength and support the nucleus.

Function of the centrosome?

Organizes spindle fibers during cell division (contains centrioles).

Function of cilia?

Short, hairlike projections that move substances (found in respiratory tract).

Function of flagella?

Long whip-like structure for cell movement (sperm tail).

Function of pseudopods?

Temporary extensions used for movement and engulfing particles.

What are the main components of the nucleus?

Nuclear envelope, nucleolus, and chromatin.

What does the nuclear envelope do?

Separates nucleus from cytoplasm; allows selective passage via pores.

What is the function of the nucleolus?

Produces ribosomes.

What is chromatin?

Loosely coiled DNA and proteins storing genetic information.

What are chromosomes?

Condensed chromatin visible during cell division.

What does selectively permeable mean in transport?

Allows certain molecules to cross depending on size, charge, or solubility.

What are the two main types of transport?

Passive: No ATP required (diffusion, osmosis, filtration).

Active: Requires ATP (active transport, endocytosis, exocytosis).

What is diffusion?

Movement of molecules from high to low concentration (e.g., O₂ and CO₂).

What is osmosis?

Diffusion of water through a selectively permeable membrane.

What is filtration?

Movement of particles through a membrane by pressure (e.g., in capillaries).

What is tonicity?

How solution concentration affects cell volume.

Define isotonic, hypertonic, and hypotonic.

Isotonic: Equal solute; no water movement.

Hypertonic: Higher solute outside; cell shrinks.

Hypotonic: Lower solute outside; cell swells.

What is active transport?

Movement from low to high concentration using ATP (e.g., Na⁺/K⁺ pump).

What is endocytosis?

Cell engulfs material into a vesicle.

What are the three types of endocytosis?

Pinocytosis: Engulfs liquid droplets.

Phagocytosis: Engulfs solid particles.

Receptor-mediated: Engulfs specific substances bound to receptors.

What is exocytosis?

Vesicles fuse with the membrane to release contents (e.g., neurotransmitters).

What is transcytosis?

Combines endocytosis and exocytosis to move substances across cells (e.g., HIV transport).

What are the three stages of the cell cycle?

Interphase, Mitosis, and Cytokinesis.

What happens during interphase?

Growth, DNA replication, and preparation for division.

What occurs in the S phase of interphase?

DNA replication.

What occurs in G1 and G2 phases?

Growth and synthesis of organelles and molecules.

What happens in prophase?

Chromatin condenses, spindle fibers form, nuclear membrane breaks down.

What happens in metaphase?

Chromosomes align at the equator of the cell.

What happens in anaphase?

Sister chromatids separate and move toward opposite poles.

What happens in telophase?

Nuclear membranes reform and chromosomes de-condense into chromatin.

What is cytokinesis?

Division of cytoplasm forming two identical daughter cells.

What is differentiation?

Process by which cells become specialized.

What are stem cells?

Undifferentiated cells capable of self-renewal or becoming many cell types.

What are progenitor cells?

Partially specialized cells that can form limited cell types (“committed” cells).

What is apoptosis?

Programmed cell death (normal, protective).

What is necrosis?

Cell death due to injury or damage (not normal).

List characteristics of cancer cells.

Loss of cell cycle control

Dedifferentiation

Uncontrolled growth

Angiogenesis (new blood vessel formation)

Metastasis (spreading)

Resistance to cell death