Cell Biology Quiz - Prokaryotes vs. Eukaryotes

Cell Structure and Function

• The image shows a historical depiction of Thames water, labeled "Monster Soup," meant to represent the inaccuracies in understanding cells prior to proper technology.
• Knowledge advances have led to improved understanding of cells.
• Cells generally are small or have an increased surface area.
• Membranes within cells form compartments for different processes.
• Endomembrane systems are a group of related organelles involved in lipid assembly, polypeptide chain modification, and product sorting/shipping.
• Endosymbiotic theory suggests that mitochondria and chloroplasts evolved from prokaryotes.
• There are similarities and differences between prokaryotic and eukaryotic cells.

Major Cell Themes

• Technological advances improve cell knowledge.
• Cells need a high surface area to volume ratio.
• Membranes create cellular compartments.
• Endomembrane systems are important for efficient cellular processes.
• Endosymbiotic theory explains the origin of mitochondria and chloroplasts.
• Prokaryotic and eukaryotic cells differ in their structures and function.

Early Cell Discoveries

• Hooke (mid-1600s) observed and described "cells" in cork.
• Leeuwenhoek (late-1600s) observed "animalcules" (living cells).
• Brown identified and named plant cells in the early 1800s.

Cell Theory

• All organisms are composed of one or more cells (Schwann).
• Cells are the smallest units with life characteristics (Schleiden).
• Cells arise from pre-existing cells (Virchow).

Two Types of Cells

Prokaryotic Cells

• Lack organelles.
• Cytoplasm contains ribosomes.
• DNA is in a nucleoid region.
• May have external structures like cell walls or capsules.
• Eubacteria and Archaea are examples.

Eukaryotic Cells

• Contain organelles with specialized functions.
• DNA is enclosed in a nucleus.
• Some have cell walls (e.g., plant cells).
• Animal, plant, fungi, and protists are examples.

All Cells: General Characteristics

• Smallest units of life.
• Can survive independently or as part of a larger organism.
• Highly organized for metabolism.
• Sense and respond to their environment.
• Can reproduce.

Cell Membranes

• The main component of cell membranes is a lipid bilayer (two layers of phospholipids).
• The lipid bilayer gives membranes their fluid properties.
• Phospholipids have a hydrophilic head and hydrophobic tails.

Cell Size and Surface Area-to-Volume Ratio

• Cells are small to maintain a favorable surface area-to-volume ratio.
• Cell volume determines metabolic activity relative to time.
• Surface area determines the number of substances entering or leaving the cell.

Ribosomes

• Cells manufacture polypeptides with ribosomes.
• Ribosomes are not membrane-bound in eukaryotes, but can be free in cytoplasm, attached to endoplasmic reticulum, or inside mitochondria/chloroplasts.
• In prokaryotic cells, ribosomes freely float within cytoplasm.
• Ribosomes consist of ribosomal RNA and provide sites for protein synthesis.

Microscopes

Light Microscopes

• Create detailed images of small things otherwise too small to see.
• Can be simple or compound.
• Resolution is limited by the wavelength of light (about 200 nanometers).

Electron Microscopes

• Use accelerated electron beams instead of light.
• Electrons are focused by magnets instead of glass lenses.
• Resolution is far greater than light microscopes.
• Types of electron microscopes include scanning electron (SEM) and transmission electron (TEM).

Eukaryotic Cells

• Contain a nucleus and other organelles.
• Include the kingdoms of plants, animals, protists, and fungi.

Organelles

• Benefit of organelles is cellular compartmentalisation to allow specific processes to occur in distinct areas.

Animal Cell Features (examples)

• Nucleus
• Nuclear envelope
• Nucleolus
• Chromatin
• Smooth and Rough Endoplasmic Reticulum
• Ribosomes
• Golgi apparatus
• Lysosomes
• Mitochondria
• Cytosol
• Centrioles
• Centrosome
• Microvilli
• Intermediate filaments
• Microtubules
• Peroxisomes

Plant Cell Features (examples)

• Cell wall
• Plasma membrane
• Nucleus
• Nuclear envelope
• Nucleolus
• Rough and Smooth Endoplasmic Reticulum
• Ribosomes
• Golgi apparatus
• Mitochondria
• Chloroplasts
• Vacuoles
• Cytosol
• Intermediate filaments
• Microtubules

Nucleus: Structure and Function

• Keeps DNA separate from cytoplasm.
• Facilitates DNA organization and replication.

Nuclear Envelope

• Composed of two lipid bilayers.
• The innermost surface has DNA attachment sites.

Endomembrane System: Components

• Endoplasmic reticulum
• Vesicles
• Golgi Apparatus

Endoplasmic Reticulum

• Continuous with nuclear membrane in animal cells.
• Rough ER modifies polypeptides.
• Smooth ER synthesizes lipids, metabolizes carbohydrates, and detoxifies.

Golgi Body

• Receives proteins from ER.
• Modifies, packages, sorts proteins.
• Adds carbohydrates to proteins.
• Synthesizes polysaccharides (plants).
• Packages material for final destinations.

Vesicles

• Transports material within cytoplasm (e.g., lysosomes, transport, peroxisomes).

Dynamic Cell Membranes

• Consistently being made, recycled, and decomposed.

Mitochondria and Chloroplasts

• ATP-producing "powerhouses."
• Have internal compartments.
• The machinery for ATP production is embedded in the inner mitochondrial membrane.
• Convert sunlight energy to the energy of organic sugars.

Endosymbiotic Theory

• Mitochondria and chloroplasts have features resembling bacteria.
• Have their own DNA and ribosomes.
• Divide independently.
• Likely evolved by being engulfed by larger prokaryotic cells but not digested.

Specialized Plant Organelles

• Plastids (chromoplasts, amyloplasts)
• Central vacuole

Other Plastids

• Chromoplasts: Lack chlorophyll, abundant carotenoids; color fruits/flowers.
• Leucoplasts: Lack pigments; store starch.

Apoptosis

• Programmed cell death involving the sequence of events to destroy a cell.
• Nucleus fragments, cell membrane blisters or blebs form, and cell fragments are engulfed by cells.
• Caspases (enzymes) cause apoptosis.
• Mitosis and apoptosis are opposing forces.

Autophagy

• Self-eating process of cells engulfing parts and recycling them.

Cytoskeleton

• Present in all eukaryotic cells; basis of shape and internal organization.
• Allows organelle and cell movement (motility).

Cytoskeleton Elements

• Microtubules
• Microfilaments
• Intermediate filaments

Microtubules

• Largest components of cytoskeleton.
• Composed of tubulin.
• Involvement in shape, motility, and cell division.

Microfilaments

• Thinnest cytoskeletal elements.
• Composed of actin.
• Movement, formation, and maintenance of cell shape.

Intermediate Filaments

• Only in animal cells of certain tissues.
• Most stable cytoskeletal elements.

Motor Proteins

• Kinesins and dyneins; move along microtubules.
• Myosins; move along microfilaments.

Flagella and Cilia

• Structures for cell motility.
• 9 + 2 internal structure (microtubules).

Plant Cell Walls

• Secondary cell wall (made of cellulose and lignin)
• Primary cell wall (made of polysaccharides, glycoproteins, and cellulose)
• Plant cells are connected by plasmodesmata.

Plant Cuticle

• Cell secretions and waxes form a layer covering the surface of the plant cell.
• Semitransparent.
• Restricts water loss.

Matrices between Animal Cells

• Hold cells together in tissues
• Contributes to properties of cartilage, skin and other tissues.
• Filters materials.
• Orients cell movement.

Plant Cell Junctions

• Plasmodesmata connect adjacent plant cells.
• The plasma membranes of adjacent cells are continuous.
• Water and solutes pass freely between cells.

Animal Cell Junctions

• Tight junctions: anchor cells together to form tissues.
• Desmosomes: anchor tissue cells and allow cells to stretch.
• Gap junctions: communication between cells.

Prokaryotic Cells

• Two kingdoms: Archaea and Eubacteria.
• DNA not enclosed in a nucleus (nucleoid region).
• Plasmids: small circular pieces of DNA.
• Generally the smallest, simplest cell type.
• Lack organelles but possess ribosomes.
• Some have flagella but structure differs from eukaryotic flagella.

Prokaryotic Cell Structures

• Capsule, cell wall, plasma membrane, cytoplasm, inclusions, ribosomes, plasmids, flagella, and pili are components of prokaryotic cells.