Chapter 04 Lecture Outline: The Cell (Integrative Approach)

Flashcards covering key cell structure and function topics from Chapter 04 of the Integrative Approach biology textbook.

What is the range in size of human cells?

Approximately 10 to 100 micrometers in diameter.

What shapes may human cells exhibit?

Spherical/round, discoid, cuboidal, columnar, fusiform, and stellate (star-shaped).

What are the three main structural features of a cell?

Plasma membrane, cytoplasm, and nucleus.

What is the difference between membrane-bound and non-membrane-bound organelles?

Membrane-bound organelles are enclosed by membranes (e.g., mitochondria, ER, Golgi, lysosomes, peroxisomes); non-membrane-bound organelles lack membranes (e.g., ribosomes, centrosomes, proteasomes, cytoskeleton).

What general functions must cells perform?

Obtain nutrients and energy, synthesize biomolecules, maintain homeostasis, respond to the environment, and reproduce (cell division) as needed.

Name the lipid components of the plasma membrane and their actions.

Phospholipids form the bilayer; cholesterol stabilizes membrane fluidity; glycolipids contribute to cell recognition and stability.

What are the two main types of membrane proteins based on their position?

Integral (transmembrane) proteins that span the membrane; peripheral proteins attached to the membrane surface.

List the six major roles of membrane proteins.

Transport (channels/carriers), enzymatic activity, signal transduction, cell‑cell recognition, intercellular joining, and attachment to cytoskeleton/ECM.

Define diffusion.

The passive movement of molecules from regions of high concentration to low concentration due to random molecular motion.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion moves small nonpolar molecules directly through the lipid bilayer; facilitated diffusion uses membrane proteins (channels or carriers) to transport hydrophilic or larger molecules down their concentration gradient.

Define osmosis and osmotic pressure.

Osmosis is the diffusion of water across a semipermeable membrane; osmotic pressure is the pressure required to prevent water movement due to solute differences.

What is the relationship between osmosis and tonicity?

Tonicity describes the effect of a solution on cell volume (isotonic, hypotonic, hypertonic); osmosis explains the water movement causing that volume change.

Differentiate primary and secondary active transport.

Primary active transport uses direct energy from ATP to pump ions; secondary active transport uses the ion gradient established by primary transport to drive transport of other substances.

Describe vesicular transport types.

Exocytosis releases substances via vesicle fusion with the plasma membrane; endocytosis includes phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Define resting membrane potential (RMP).

The electrical potential difference across the cell membrane when the cell is at rest, typically negative inside (about −70 mV in many cells).

What cellular conditions are significant for establishing and maintaining an RMP?

Stable ion gradients (Na+, K+, Ca2+), selective membrane permeability, presence of leak channels, and Na+/K+ ATPase activity.

Describe the structure and main function of mitochondria.

Double-membrane-bound organelle; site of aerobic cellular respiration; produces most ATP—the cell’s powerhouses.

Describe the structure and main function of the rough and smooth endoplasmic reticulum.

Rough ER has ribosomes and synthesizes secreted/membrane proteins; Smooth ER synthesizes lipids and detoxifies; both form part of the endomembrane system.

Describe the structure and main function of the Golgi apparatus.

Stack of flattened sacs that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles; forms secretory vesicles.

Describe the structure and function of lysosomes.

Membranous sacs with digestive enzymes that digest endocytosed material and unneeded substances.

Describe the structure and function of peroxisomes.

Membrane-enclosed sacs containing enzymes for beta-oxidation of fats and detoxification; contain catalase to break down hydrogen peroxide.

Describe the structure and function of ribosomes.

Non-membrane-bound particles that synthesize proteins by translating mRNA.

Describe the structure and function of the centrosome.

Organelle that organizes microtubules during cell division; contains a pair of centrioles in animal cells.

Describe the structure and function of proteasomes.

Protein complexes that degrade damaged or unneeded proteins via proteolysis.

Describe the structure and function of the cytoskeleton.

Network of protein filaments (microfilaments, intermediate filaments, microtubules) that provides support, enables movement, and facilitates transport.

What are microvilli?

Membrane protrusions that increase surface area for absorption; supported by actin filaments.

Differentiate cilia and flagella.

Cilia are short, numerous projections that move substances across cell surfaces; flagella are long, few in number and used for cell movement.

What are the three major types of membrane junctions?

Tight junctions (occlude passage), desmosomes (spot welds), gap junctions (channels for intercellular communication).

Describe the structure of the nucleus and the nucleolus.

Nucleus is bounded by the nuclear envelope; the nucleolus is a region where rRNA synthesis and ribosome assembly occur.

Describe the relationship of DNA, chromatin, and genes.

DNA is genetic material; chromatin is DNA wrapped around histones; genes are specific DNA sequences that code for proteins or functional products.

List the required structures for transcription.

DNA template, RNA polymerase, transcription factors, promoter region (plus energy from nucleotides).

What are the three steps of transcription?

Initiation, elongation, termination.

List the required structures for translation.

mRNA, tRNA, ribosomes, amino acids, initiation/elongation/termination factors, and energy (GTP).

Name the three functional forms of RNA, define codon, and identify stop/start codons.

RNA forms: mRNA, tRNA, rRNA; codon is a three-nucleotide sequence on mRNA coding for an amino acid; start codon is AUG; stop codons are UAA, UAG, UGA.

Describe the three steps of translation.

Initiation, elongation, termination.

Why is DNA considered the cell’s control center?

Because it stores the genetic instructions for protein synthesis and regulates cellular activities via gene expression.

Describe the difference between chromatin and chromosomes and when each is present.

Chromatin is loosely packed DNA-protein; chromosomes are tightly condensed DNA during mitosis; chromatin is present during interphase.

Outline the phases of the cell cycle and activities in each phase.

Interphase (G1, S, G2) with growth and DNA replication; M phase with mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis.

What are the major events of prophase in mitosis?

Chromatin condenses into chromosomes; nucleolus disappears; spindle apparatus forms; centrosomes move apart; nuclear envelope breaks down.

What are the major events of metaphase in mitosis?

Chromosomes align at the metaphase plate; spindle fibers attach to kinetochores.”

What are the major events of anaphase in mitosis?

Sister chromatids separate and move to opposite poles; cell elongates as microtubules lengthen (and shorten at kinetochores).

What are the major events of telophase and cytokinesis?

Telophase: chromosomes arrive at poles, de-condense; nuclear envelope and nucleolus re-form; spindle breaks down. Cytokinesis divides cytoplasm, producing two daughter cells.

What is the function of channel-linked receptors?

Open ion channels in response to ligand binding, initiating rapid changes in membrane permeability and potential.

What is the function of enzymatic receptors?

Receptors with intrinsic enzyme activity or that activate kinases to phosphorylate substrates, altering cellular activity.

What is the function of G protein–coupled receptors (GPCRs)?

Transduce signals by activating G proteins that regulate enzymes or ion channels, initiating signaling cascades.

Why is the plasma membrane described as a dynamic, selectively permeable barrier?

It regulates what enters and leaves the cell, supports cell integrity, and hosts membrane proteins for transport, signaling, and interactions.