Bio111 Chapter 4 Fletcher

Cells

Basic unit of life; smallest structure capable of life

Cell theory

• All organisms made of cells

• Life processes occur in cells

• Cells come from pre-existing cells

• DNA is hereditary material in cells

Two cell types

Prokaryotic cells and eukaryotic cells

Four components all cells have

Plasma membrane, cytoplasm, DNA, ribosomes

Cell function in organisms

Cells work together → tissues → organs → emergent properties

Emergent properties

New functions that arise from cell cooperation (communication, structure, specialization)

Light microscopy

Uses visible light; ~200 nm resolution; live or fixed cells

Electron microscopy

Uses electrons; ~0.1–1 nm resolution; fixed samples only

Transmission EM

2D internal cell structures

Scanning EM

3D surface structure imaging

Prokaryotes

Cells without membrane-bound organelles; unicellular

Prokaryotic DNA

Single circular chromosome in nucleoid region

Prokaryotic cell wall function

Protection, shape, osmotic balance

Prokaryotic cell wall composition

Bacteria: peptidoglycan
Archaea: pseudopeptidoglycan

Gram positive bacteria

Thick peptidoglycan; no outer membrane

Gram negative bacteria

Thin peptidoglycan; outer membrane present

Prokaryotic size range

0.1–10 µm

Prokaryotic reproduction

Binary fission (asexual cell division)

Binary fission steps

DNA replication → cell elongation → membrane pinches → two identical cells

Prokaryotic metabolism location

Cytoplasm (no organelles needed)

Prokaryotic cell shape types

Coccus (sphere), bacillus (rod), spirillum (spiral)

Largest biological population

Prokaryotes (bacteria dominate)

Bacteria characteristics

Common, diverse, some pathogenic, many beneficial

Archaea characteristics

Extremophiles; non-pathogenic; found in normal + extreme environments

Shared features of bacteria & archaea

No nucleus, unicellular, cell wall, binary fission

Differences bacteria vs archaea

Membrane chemistry, cell wall structure, evolutionary lineage

Eukaryotic cell definition

Cells with membrane-bound organelles and nucleus

Eukaryotic DNA

Linear chromosomes in nucleus

Eukaryotic size range

10–100 µm

Common eukaryotic organelles

Nucleus, mitochondria, ER, Golgi, ribosomes, vesicles

Mitochondria function

ATP production (energy generation)

Nucleus function

Stores DNA; controls gene expression; transcription site

Nucleolus function

Makes rRNA and assembles ribosomes

Rough ER function

Protein synthesis + modification (ribosome attached)

Smooth ER function

Lipid synthesis, detoxification, Ca²⁺ storage

Golgi apparatus function

Modifies, sorts, packages proteins/lipids

Vesicles function

Transport materials within cell

Vacuole function

Storage (larger in plant cells)

Peroxisomes function

Break down fatty acids; detoxify; produce H₂O₂

Endomembrane system

Group of organelles working together to modify + transport molecules

endomembrane system includes:

Nuclear envelope, ER, Golgi, vesicles, lysosomes, plasma membrane

Plant-only structures

Cell wall, chloroplasts, central vacuole, plasmodesmata

Animal-only structures

Lysosomes, centrosomes

Cell wall function

Support, protection, rigidity

Chloroplast function

Photosynthesis (glucose production)

Central vacuole function

Water storage, turgor pressure regulation

Cytoskeleton

Protein fiber network for shape, movement, transport

Microfilaments

Actin; movement + muscle contraction

Microtubules

Cell division, cilia/flagella structure

Intermediate filaments

Structural support and stability

Tight junctions

Seal cells; prevent leakage

Desmosomes

Mechanical strength; connect intermediate filaments

Gap junctions

Cell communication channels (animals)

Plasmodesmata

Plant cell communication channels

Extracellular matrix (ECM)

Protein + polysaccharide network outside cell; support + signaling

Plasma membrane components

Phospholipids, proteins, carbohydrates, sterols

Function of membrane

Selective barrier, communication, transport

Selective permeability

Controls what enters/exits cell

Organelle surrounded by two membranes

Nucleus (nuclear envelope)

Which cells have ribosomes

All cells (prokaryotic + eukaryotic)

Only eukaryotic organelles

Nucleus + membrane-bound organelles

Organelle malfunction in Tay-Sachs

Lysosome

Most smooth ER

Steroid-producing cells

Protein secretion pathway order

RER → vesicle → Golgi → vesicle → membrane

Endocytosis definition

Cell engulfs material into vesicle