Bio 131 - Exam 1 - Introduction to Cells (endomembrane system, endosymbiotic theory, cytoskeletal proteins, cell junctions

Why is compartmentalization important in eukaryotic cells?

It separates cellular processes into specialized spaces, allowing different functions to occur efficiently.

How are membranes of the endomembrane system related?

They are connected directly or exchange membrane and materials through vesicles.

Which organelles and membranes make up the endomembrane system?

The nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane.

How is the nuclear envelope connected to the ER?

The nuclear envelope is continuous with the rough ER, which is continuous with the smooth ER.

How do proteins and membranes move from the ER to the Golgi apparatus?

Transport vesicles carry them from the ER to the Golgi.

What happens to proteins as they pass through the Golgi apparatus?

They are modified, sorted, and packaged for delivery.

What structures can arise from vesicles produced by the Golgi?

Lysosomes, specialized vesicles, and vacuoles.

How do lysosomes digest material in other vesicles?

They fuse with the vesicles and use digestive enzymes to break down their contents.

How are proteins delivered to the plasma membrane for secretion?

Transport vesicles carry them to the plasma membrane.

What is exocytosis?

A vesicle fuses with the plasma membrane and releases its contents outside the cell.

How does vesicle fusion expand the plasma membrane?

The vesicle’s membrane becomes part of the plasma membrane.

What is the general pathway for a protein secreted through the endomembrane system?

Rough ER → transport vesicle → Golgi apparatus → secretory vesicle → plasma membrane → outside the cell.

What is the main function of mitochondria?

They carry out cellular respiration, using energy from nutrients to generate ATP.

What is the role of oxygen in aerobic cellular respiration?

It serves as the final electron acceptor in the electron transport chain.

Where are mitochondria found?

In nearly all eukaryotic cells.

What are the two membranes of a mitochondrion like?

The outer membrane is smooth, and the inner membrane is folded into cristae.

What are cristae?

Folds of the inner mitochondrial membrane.

Why are cristae important?

They increase the surface area available for the machinery that produces ATP.

What two compartments are formed by mitochondrial membranes?

The intermembrane space and the mitochondrial matrix.

What is the mitochondrial intermembrane space?

The space between the outer and inner mitochondrial membranes.

What is the mitochondrial matrix?

The compartment enclosed by the inner mitochondrial membrane.

What occurs in the mitochondrial matrix?

Some steps of cellular respiration, including the citric acid cycle.

What is the main function of chloroplasts?

They carry out photosynthesis, converting light energy into chemical energy stored in organic molecules.

Which organisms contain chloroplasts?

Plants and algae.

What are thylakoids?

Membranous sacs inside chloroplasts.

What is a granum?

A stack of thylakoids; the plural is grana.

What is the stroma?

The fluid surrounding the thylakoids inside a chloroplast.

What are plastids?

A group of organelles found in plants and algae that includes chloroplasts.

What does the endosymbiotic theory explain?

The evolutionary origins of mitochondria and chloroplasts from bacteria that lived inside ancestral host cells.

How did mitochondria originate according to the endosymbiotic theory?

An ancestral host cell engulfed a nonphotosynthetic bacterium that became an endosymbiont and eventually a mitochondrion.

How did chloroplasts originate according to the endosymbiotic theory?

A cell whose lineage already had mitochondria engulfed a photosynthetic bacterium that eventually became a chloroplast.

What evidence supports the endosymbiotic theory?

Mitochondria and chloroplasts have double membranes, their own circular DNA, bacterial-like ribosomes, and the ability to grow and divide within cells.

Are mitochondria and chloroplasts completely independent of the cell?

No. They can grow and divide within cells but depend on the host cell for many proteins and resources.

What is the cytoskeleton?

A network of protein fibers extending throughout the cytoplasm.

What are the main functions of the cytoskeleton?

Maintaining cell shape, organizing and anchoring structures, moving organelles, and supporting cell movement.

Why is the cytoskeleton described as dynamic?

Its components can be assembled, disassembled, and reorganized as the cell’s needs change.

What are motor proteins?

Proteins that use ATP to generate movement, often by moving along cytoskeletal fibers.

How do motor proteins transport vesicles?

They attach to vesicles and move them along microtubules or actin filaments using ATP.

What are the three main components of the cytoskeleton?

Microtubules, microfilaments, and intermediate filaments.

How do cytoskeletal fibers compare in thickness?

Microtubules are thickest, intermediate filaments are in the middle, and microfilaments are thinnest.

What are microtubules made of?

Tubulin dimers assembled into hollow rods.

What are the main functions of microtubules?

Supporting cell shape, guiding organelle movement, and separating chromosomes during cell division.

What is a centrosome?

A microtubule-organizing center near the nucleus in animal cells.

What structures are typically found within an animal cell’s centrosome?

A pair of centrioles.

What is the microtubule arrangement in a centriole?

Nine triplets of microtubules arranged in a ring.

What are cilia and flagella?

Cell extensions containing microtubules that can move the cell or surrounding fluid.

How do cilia and flagella differ in number and length?

Cilia are generally shorter and numerous, while flagella are generally longer and limited to one or a few per cell.

How do cilia and flagella differ in movement?

Cilia typically use power and recovery strokes, while flagella typically move with an undulating motion.

What surrounds the microtubules in a cilium or flagellum?

The plasma membrane.

What is a basal body?

A structure that anchors a cilium or flagellum.

Which motor protein drives the bending of cilia and flagella?

Dynein.

What supplies the energy for cilia and flagella to bend?

ATP hydrolysis.

What are microfilaments made of?

Globular actin subunits assembled into thin, solid rods.

What is another name for microfilaments?

Actin filaments.

What forces do microfilaments resist?

Tension, or pulling forces.

Which cytoskeletal fibers form the core of intestinal microvilli?

Bundles of actin microfilaments.

What are microvilli?

Plasma membrane projections that increase surface area, especially for absorption.

Which motor protein interacts with actin during cellular movement?

Myosin.

What are examples of movement involving actin and myosin?

Muscle contraction, amoeboid movement, and cytoplasmic streaming.

What is amoeboid movement?

Cell movement using temporary extensions of the cell, supported by changes in the actin cytoskeleton.

What is cytoplasmic streaming?

The circulation of cytoplasm within a cell, helping distribute materials.

What are the main functions of intermediate filaments?

Reinforcing cell shape and anchoring organelles.

How stable are intermediate filaments compared with other cytoskeletal fibers?

They are generally more permanent and stable than microtubules and microfilaments.

What are extracellular materials?

Materials produced by cells and located outside the plasma membrane.

What are the main functions of a plant cell wall?

Protecting the cell, maintaining its shape, and preventing excessive expansion as water enters.

What are plant cell walls made of?

Cellulose microfibrils embedded in other polysaccharides and proteins.

What is the primary cell wall?

A relatively thin, flexible wall formed as a plant cell grows.

What is the middle lamella?

A thin layer between the primary walls of adjacent plant cells that helps hold them together.

What is the secondary cell wall?

An additional wall deposited between the plasma membrane and primary cell wall in some plant cells.

What is the order of plant cell wall layers from outside toward the plasma membrane when all are present?

Middle lamella → primary cell wall → secondary cell wall → plasma membrane.

What extracellular structure surrounds many animal cells?

The extracellular matrix, or ECM.

What are major components of the animal extracellular matrix?

Collagen, proteoglycans, and fibronectin.

What are integrins?

Cell-surface receptor proteins that connect the extracellular matrix to the cell’s interior.

What are major functions of the extracellular matrix?

Providing support and helping regulate cell adhesion, movement, and signaling.

What are cell junctions?

Structures that connect neighboring cells and allow them to adhere, interact, or communicate.

Which cell connections are found in plants?

Plasmodesmata.

What are plasmodesmata?

Channels through plant cell walls that connect the cytoplasm of adjacent cells.

What can pass through plasmodesmata?

Water, small solutes, and sometimes proteins and RNA.

What are the three main types of junctions in animal cells?

Tight junctions, desmosomes, and gap junctions.

Where are animal cell junctions especially common?

In epithelial tissue.

What is the function of tight junctions?

They seal neighboring cells together to prevent substances from leaking between them.

What is the function of desmosomes?

They anchor neighboring cells together, helping tissues resist mechanical stress.

Which cytoskeletal fibers are connected to desmosomes?

Intermediate filaments.

What is the function of gap junctions?

They form channels that allow ions and small molecules to pass directly between neighboring animal cells.

Which plant and animal cell connections allow direct communication between neighboring cells?

Plasmodesmata in plants and gap junctions in animals.

How can you remember the functions of animal cell junctions?

Tight junctions seal, desmosomes anchor, and gap junctions communicate.

What does it mean that a cell is greater than the sum of its parts?

Cell functions emerge from coordinated interactions among its components.

How do cell components cooperate when a macrophage destroys bacteria?

The plasma membrane engulfs bacteria, the cytoskeleton supports movement and engulfment, and lysosomes digest the bacteria.