Chapter 3: The Cell (Video Notes)

flashcards cover prokaryotic vs. eukaryotic cell features, spontaneous generation, cell theory, endosymbiotic theory, prokaryotic structures (nucleoid, plasmids, cell wall, membranes), adhesion and transfer structures (fimbriae, pili), endospores, endomembrane system, organelles, cytoskeleton, and basic motility structures.

What is the basic criterion that separates prokaryotic cells from eukaryotic cells?

Presence or absence of a true nucleus; prokaryotes lack a membrane-bound nucleus, while eukaryotes have one.

What is the nucleoid in bacteria?

The region where the single circular chromosome is located; it is not bounded by a membrane.

What are plasmids?

Circular pieces of DNA that carry non-essential genes, such as antibiotic resistance or toxins.

What is a ribosome in prokaryotes and its size?

70S ribosomes, consisting of 30S small subunit and 50S large subunit.

What is an inclusion in prokaryotic cells?

Storage structures for excess nutrients or molecules (e.g., glycogen, starch, iron); some may contain gas for buoyancy.

What is a capsule in bacteria?

A protective, gelatinous layer surrounding some bacteria.

What are fimbriae?

Bristle-like, numerous surface structures used for adhesion.

What are pili?

Longer, singular structures involved in genetic transfer (e.g., conjugation) and sometimes adhesion.

What is the role of the bacterial cell wall?

Provides shape and protection; typically made of peptidoglycan and differs between Gram-positive and Gram-negative envelopes.

How do Gram-positive and Gram-negative cell walls differ?

Gram-positive: thick peptidoglycan with teichoic acids and one membrane. Gram-negative: thin peptidoglycan, inner and outer membranes, LPS, porins, and periplasmic space.

What are teichoic acids?

Components associated with thick peptidoglycan in Gram-positive cell walls.

What is LPS and where is it found?

Lipopolysaccharide in the outer membrane of Gram-negative bacteria; includes O antigen and lipid A.

What are porins?

Proteins in the outer membrane that form channels for molecule passage.

What is the Endosymbiotic Theory?

Mitochondria and chloroplasts originated from free-living bacteria engulfed by a host cell; supported by their own DNA and ribosomes; two events: aerobic bacteria became mitochondria and photosynthetic bacteria became chloroplasts.

Who coined the term 'cell'?

Robert Hooke in 1665, while looking at cork tissue.

What are the two core statements of modern cell theory?

1) Cells are the fundamental unit of life. 2) All cells come from other cells.

Which scientist proposed that plants and animals are made of cells and that cells beget cells?

Theodore Schwann.

What did Robert Brown contribute to cell biology?

First to describe nuclei in eukaryotic cells.

What is the Endomembrane System?

A network of membrane-bound organelles (rough ER, smooth ER, Golgi, lysosomes, vesicles) that synthesize, modify, and transport proteins and lipids.

What is the rough endoplasmic reticulum (RER) and its function?

ER with ribosomes; site of protein synthesis and initial folding.

What is the smooth endoplasmic reticulum (SER) and its function?

ER lacking ribosomes; site of lipid synthesis, carbohydrate metabolism, and detoxification.

What is the Golgi apparatus responsible for?

Modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

What are lysosomes?

Organelles containing digestive enzymes that degrade food particles and cellular debris.

What are peroxisomes?

Organelles that break down uric acid, amino acids, and fatty acids with hydrogen peroxide; not part of the endomembrane system.

What are mitochondria responsible for?

Main site of aerobic respiration and ATP production; contain their own DNA and ribosomes and have cristae in the inner membrane.

What are chloroplasts and what is their function?

Site of photosynthesis; contain thylakoids (grana) and stroma; have their own DNA and ribosomes.

What is the nucleus and what does it contain?

A membrane-bound organelle containing genetic material (chromosomes) surrounded by the nuclear envelope with nuclear pores; contains the nucleolus for rRNA synthesis.

What is the nucleolus?

A substructure within the nucleus where ribosomal RNA is synthesized and ribosomes begin to assemble.

What are ribosomes in eukaryotes vs prokaryotes?

Prokaryotes have 70S ribosomes (30S+50S). Eukaryotes have 80S ribosomes (40S+60S); mitochondria and chloroplasts contain 70S ribosomes.

What is the endomembrane system’s relation to protein and lipid transport?

It coordinates synthesis, modification, and transport of proteins and lipids throughout the cell.

What is the role of the cytoskeleton?

Maintains cell shape, provides tracks for transport, and anchors organelles; composed of microtubules, microfilaments, and intermediate filaments.

What are microtubules, microfilaments, and intermediate filaments made of and their sizes?

Microtubules: tubulin dimers, about 25 nm. Microfilaments: actin filaments, about 7 nm. Intermediate filaments: fibrous proteins, about 8–12 nm.

What is the 9+2 arrangement in flagella and cilia?

A microtubule arrangement where there are nine doublets around a central pair; they are composed of tubulin and enable motility.

How do bacteria move and what is run vs tumble?

Movement involves flagellar rotation; run is a straight swim (flagella rotate counterclockwise and bundle); tumble is a reorientation (clockwise rotation causing flagella to fall apart).