bio 2311 ch 4

2 cell types?

prokaryotic + eukaryotic

What are the major characteristics of all life?

• Cellular organization

• DNA / heredity

• Growth & development

• Reproduction

• Metabolism

• Response to environment

• Transport

Eukaryotic cells

Nucleus + membrane-bound organelles

Prokaryotic cells

NO nucleus or membrane-bound organelles

eukaryote organisms

animals, plants, fungi, protists

Prokaryote organisms

bacteria + archaea

bacteria + archaea

Magnification = how BIG? 🔍
Resolution = how CLEAR? 👀

TEM vs. SEM? (microscope)

TEM → inside the cell
SEM → surface of the cell

light vs. electron microscopy — which gives more detail?

electron microscopy

→ much higher resolution than light microscopy.

What limits cell size?

As cell size ↑ → SA:V ratio ↓

As cell size ↑ → SA:V ratio ↓

Allows more efficient exchange of substances between the cell and environment.

What is the plasma membrane made of?

Phospholipid bilayer + embedded proteins

Why is the phospholipid bilayer a barrier to water-soluble substances?

Its interior is hydrophobic.

→ Water-soluble substances often need _______ to cross.

transport proteins

Why is selective membrane transport important?

Maintains the cell’s specialized internal environment.

selectively permeable

The membrane allows some substances to cross but blocks others.

What are major functions of the cell membrane?

• Controls nutrients in / wastes out

• Site of some energy reactions & synthesis

• Maintains the cell’s internal environment

Where is a cell’s hereditary information stored?

DNA (genes) in the cell’s central region.

cytoplasm?

Everything between the plasma membrane and central DNA region.

cytosol?

aqueous (watery) solution containing ions and organic molecules.

cytoskeleton

• Cell division

• Chromosome separation

nucleoid?

Region in a prokaryotic cell containing DNA.

What is the prokaryotic chromosome like?

Usually one circular DNA molecule located in the nucleoid.

What are the 3 common prokaryotic cell shapes?

• Spherical

• Rodlike

• Spiral

How does genetic information become protein in a prokaryote?

DNA → mRNA → ribosome → protein

What structures are commonly found in a prokaryotic cell?

Plasma membrane, cytoplasm, nucleoid, ribosomes + cell wall

What is the glycocalyx?

A coating outside the cell wall made of sugars and/or proteins.

What are the 2 types of glycocalyx?

• Slime layer

• caspule

Slime layer

loose + loosely attached

Capsule

organized + tightly attached

What are the functions of the glycocalyx?

• Prevents dehydration/nutrient loss

• Protects from phagocytosis

• Helps attachment & biofilm formation

What is the bacterial cell envelope?

• Cell membrane

• Cell wall

→ maintains cell integrity

Gram-positive envelope

THICK peptidoglycan wall + cell membrane

Gram-negative envelope

THIN peptidoglycan + outer membrane + cell membrane

What is peptidoglycan and what does it do?

• Peptidoglycan = shape + prevents bursting

What is peptidoglycan made of?

Repeating sugars:

• NAG

• NAM

What is unique to the Gram-positive cell wall?

• Thick peptidoglycan

• Teichoic acid

• Lipoteichoic acid

What is unique to the Gram-negative cell wall?

• Thin peptidoglycan

• Periplasmic space

• Outer membrane

• LPS

LPS

Gram-negative outer membrane; endotoxin

Porins

Control what enters/leaves Gram-negative bacteria

Mycobacteria

Cell wall contains mycolic acid → acid-fast

Acid-fast stain

Used to identify Mycobacteria, including M. tuberculosis

Mycoplasma

No cell wall → variable shape (pleomorphic)

Flagella

Rotate 360° → move the cell

Pili

Attach bacteria to surfaces or other cells

Sex pilus

Connects bacteria during mating/DNA transfer

Bacterial flagellum parts

Filament → long outer part
Hook → connects
Basal body → anchors/rotates

Plasmids

Small, circular extra DNA separate from the chromosome.

What can plasmids carry?

Helpful genes like antibiotic resistance or toxin genes.

Ribosomes

Make proteins from mRNA.

Ribosome composition

60% rRNA + 40% protein

Bacterial cytoskeleton

Maintains cell shape + helps in cell division

Archaea

Prokaryotes with features similar to both bacteria + eukaryotes

Archaea cell structure

Circular DNA, nucleoid, no nucleus or membrane-bound organelles

Where are Archaea found?

Many environments, including extreme habitats

Types of extremophile Archaea

• Methanogens → produce methane

• Hyperthermophiles → extreme heat

• Halophiles → extreme salt

Archaea & human disease

No known human pathogens