BIOL1030 Exam #1 Ch.4

Cell Theory & 7 characteristics for being alive and small

• Cell Theory:

  1. All living things are made of cells.

  2. Cells are the basic unit of life.

  3. All cells come from pre-existing cells.

• Scientists: Schleiden (plants), Schwann (animals), Virchow (cells from cells).

• 7 Characteristics of Life: regulate internal environment, acquire & use energy, respond to environment, maintain organization, reproduce, ordered, adapt & evolve.

• Why small? Cells stay small to keep a high surface area:volume ratio → efficient exchange.

Types of cells and their characteristics

• Prokaryotes: small, no nucleus, found in bacteria & archaea domains.

• Eukaryotes: larger, true nucleus, organells, found in eukarya domain (plants, animals, fungi, & protists)

• Plants vs Animals:

  • Plants → chloroplasts, cell wall, large vacuoles, no centrioles.

  • Animals → lysosomes, centrioles, centrosomes.

Origin of the nucleus and the endomembrane system, ribosomes

• Origin: plasma membrane folded inward, surrounding DNA → nucleus & endomembrane system formed.

• Nucleus: control center; stores DNA; directs transcription (mRNA); nucleolus makes rRNA + ribosome subunits.

• Ribosomes: 60% rRNA + 40% protein, free or bound to ER; function in protein synthesis.

• Endomembrane system includes: nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane.

• Functions:

  • Smooth ER → lipids, detox, Ca²⁺ storage.

  • Rough ER → protein synthesis.

  • Golgi → modify, sort, ship.

  • Lysosomes → digestion, apoptosis.

  • Vacuoles → storage, water balance, support (plants).

  • Peroxisomes → oxidation, detox H₂O₂.

Prokaryote description of structures & functions

• Key structures:

  • Cell wall (peptidoglycan) → shape & protection.

  • Capsule → sticky layer for protection & attachment.

  • Fimbriae → stick to surfaces.

  • Flagella → movement.

  • Nucleoid → region with circular DNA.

  • Ribosomes → protein synthesis.

  • Cytoplasm & plasma membrane.

• Shapes: cocci (spheres), bacilli (rods), spirilla (spirals).

Eukaryote description with organelles, structures, and functions

• Nucleus → stores DNA, directs cell activities.

• Organelles:

  • Mitochondria → energy (ATP).

  • Chloroplasts (plants) → photosynthesis.

  • ER (smooth & rough).

  • Golgi → processing & shipping.

  • Vacuoles → storage & support.

  • Lysosomes (animals) → digestion.

  • Cytoskeleton → shape, movement, transport.

• Compartmentalization = efficiency.

Endosymbiont Theory with example Elysia chlorotica

• Theory: mitochondria & chloroplasts were once free prokaryotes engulfed by larger cells.

• Evidence: similar size to bacteria, divide by binary fission, have DNA & ribosomes, double membranes.

• Modern example: Elysia chlorotica (sea slug) keeps algal chloroplasts → does photosynthesis.

Organelles, structure & function (s31–36)

Mitochondria – energy converting

• Harvest energy from food (ATP).

• Matrix = Krebs cycle; cristae = electron transport chain.

• Have DNA & ribosomes.

Chloroplasts – energy converting

• Photosynthesis: convert solar → chemical energy.

• Thylakoids = light reactions; stroma = Calvin cycle.

• Have DNA & ribosomes.

Cytoskeleton

• Microtubules (α,β-tubulin), microfilaments (actin), intermediate filaments (keratin).

• Support, shape, transport, movement.

Cilia & Flagella

• “9+2” microtubule arrangement.

• Dynein motor proteins cause bending → movement.

Centrioles & Centrosomes

• Centrioles = 27 microtubules (9+0 pattern).

• Pair = centrosome → microtubule organizing center.

• Form basal bodies for cilia & flagella.

Extracellular Matrix (ECM)

• Found outside animal cells.

• Components: collagen, elastin, fibronectin, integrins.

• Functions: support, adhesion, signal transmission, wound healing.