Cell Biology Quiz: Prokaryotes vs Eukaryotes

Processes of Life

• Growth is the increase in size
• Reproduction is the increase in number
• Responsiveness is the ability to react to environmental stimuli
• Metabolism is controlled chemical reactions of organisms

Characteristics of Life and Their Distribution in Microbes

• Bacteria, Archaea, and Eukaryotes all show Growth
• Bacteria, Archaea, and Eukaryotes all show Reproduction
• Bacteria, Archaea, and Eukaryotes all show Responsiveness
• Bacteria, Archaea, and Eukaryotes all show Metabolism
• Viruses display no Growth
• Viruses use host cells for Reproduction
• Viruses show some Responsiveness in some viruses
• Viruses use host cell's Metabolism
• Viruses lack cytoplasmic membrane or cellular structure
• All have a membrane-bound structure capable of all of the functions listed above

Examples of Types of Cells

• SEM shows bacteria in image (a)
• LM shows a eukaryote in image (b)
• The SEM is 1 µm, the LM is 40 µm

Mycoplasma

• Mycoplasma can reproduce itself through binary fission, where one cell divides into two daughter cells
• Mycoplasma has metabolic processes that allow it to obtain energy and nutrients from its environment
• Mycoplasma maintain internal stability (homeostasis) despite changes in its external environment
• Mycoplasma can thrive in diverse environments and showcase its adaptation and resilience as a living organism.

Prokaryotic Cells vs Eukaryotic Cells

• Prokaryotes include bacteria and archaea
• Prokaryotes have a simpler structure
• Prokaryotes lack a nucleus
• Prokaryotes lack various membrane-bound internal structures
• Prokaryotes are typically 1.0 µm in diameter or smaller
• Eukaryotes have a nucleus
• Eukaryotes have internal membrane-bound organelles
• Eukaryotes are typically 10–100 µm in diameter
• Eukaryotes have a more complex structure
• Eukaryotes include algae, protozoa, fungi, animals, and plants

Bacterial Cell Walls

• Provide structure and shape and protect the cell from osmotic forces
• Assist some cells in attaching to other cells, or in resisting antimicrobial drugs
• Can target cell walls of bacteria with antibiotics
• Gives bacterial cells their characteristic shapes
• Composed of peptidoglycan
• Scientists describe two basic types: Gram-positive and Gram-negative

Gram-Positive Bacterial Cell Walls

• Relatively thick layer of peptidoglycan
• Contain unique polyalcohols called teichoic acids
• Appear purple following Gram staining procedure
• Presence of up to 60% mycolic acid in acid-fast bacteria helps preserve the cell during desiccation

Gram-Negative Bacterial Cell Walls

• Thin layer of peptidoglycan
• Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS)
• Lipid A portion of LPS can cause fever, vasodilation, inflammation, shock, and blood clotting
• May impede treatment of disease
• Appear pink following Gram staining procedure

Bacteria Without Cell Walls

• Some bacteria lack cell walls
• Sometimes mistaken for viruses (due to their small size and lack of cell wall)
• Have other prokaryotic features such as their ribosomes

Bacterial Cytoplasmic Membranes

• Structure
• Referred to as a phospholipid bilayer
• Composed of lipids and associated proteins
• Contains integral and peripheral proteins
• Fluid mosaic model describes current understanding of membrane structure
• Function
• Controls substances passing in and out of the cell
• Stores energy
• Harvests light energy in photosynthetic bacteria
• Selectively permeable to most substances
• Proteins allow substances to cross the membrane
• Maintains a concentration and electrical gradient

Membrane Permeability

• The cell membrane is a semi-permeable membrane
• Passes only selected components in and out
• The ease of passage is called permeability, or the rate of passive diffusion

Passive Transport: Principles of Diffusion

• Substance from region of high concentration to region of low concentration until equilibrium is met
• Simple Diffusion: Doesn't require protein helpers. Examples: movement of water, oxygen, carbon dioxide, ethanol, and urea
• Facilitated Diffusion: Needs protein helpers. Examples: transport of glucose, sodium ions, and potassium ions
• Osmosis: Spontaneous movement of water molecules from lower solute concentration to higher solute concentration via a semipermeable membrane.

Active Transport: Principles of Diffusion

• Substances are moved against concentration gradients using energy, often ATP
• Uniport is when a molecule is moved in one direction
• Antiport is when molecules move in opposite directions
• Coupled transport is when two molecules move in the same direction (symport)

Group Translocation

• Active transport in which the substance is chemically altered during transport, typically seen in bacteria

Cytoplasm of Bacteria

• Cytosol, the liquid portion mostly water
• Contains the cell's DNA in the nucleoid region
• Inclusions are chemical reserve deposits

Endospores

• Unique structures produced by some bacteria
• Defensive strategy for unfavorable conditions
• Vegetative cells transform into endospores when nutrients are limited
• Resistance to extreme conditions such as heat, radiation, and chemicals

Cytoplasm of Prokaryotes

• Nonmembranous organelles, like ribosomes
• Ribosomes are for protein synthesis
• Composed of polypeptides and ribosomal RNA
• 70S ribosome (30S and 50S)
• Many antibacterial drugs work on bacterial ribosomes, and won't affect eukaryotes
• Cytoskeleton
• Composed of three or four types of protein fibers
• Can play different roles in the cell, including cell division, cell shape, DNA segregation, and movement

External Structures of Archaea

• Glycocalyx - function in the formation of biofilms, adhere to one another and inanimate objects
• Flagella - consist of basal body, hook, and filament; numerous differences from bacterial flagella
• Fimbriae and Hami - many archaea have fimbriae and some make fimbria-like structures called hami to attach to surfaces

Archaeal Cell Walls and Cytoplasmic Membranes

• Most archaea have cell walls
• Do not have peptidoglycan
• Contain variety of specialized polysaccharides and proteins
• All archaea have cytoplasmic membrane that
• Maintains electrical and chemical gradients
• Controls import and export of substances

Cytoplasm of Archaea

• Archaeal cytoplasm is similar to bacterial cytoplasm (70S ribosomes, fibrous cytoskeleton, and circular DNA)
• Archaeal cytoplasm differs from bacterial cytoplasm in ribosomal proteins, metabolic enzymes, and genetic code features more similar to eukaryotes than bacteria