Review of Chapter 4: Cells and Organelles slides 1-65

These flashcards cover key concepts and information from Chapter 4 of Becker's World of the Cell, focusing on cell structure, function, and various cellular processes.

What are the two main types of cells?

Prokaryotes and eukaryotes

What distinguishes eukaryotic cells from prokaryotic cells?

Eukaryotic cells have a membrane-bound nucleus, while prokaryotic cells do not.

Name three types of organisms that belong to the eukaryotic domain.

Plants, animals, fungi

Why is the term 'prokaryote' considered oversimplified?

It groups bacteria and archaea together based only on the absence of a nucleus, ignoring their genetic and biochemical differences.

What type of analysis helped scientists distinguish between bacteria and archaea?

rRNA sequence analysis

What does rRNA sequence analysis reveal about the relationship between bacteria, archaea, and eukaryotes?

Bacteria and archaea are as genetically distinct from each other as they are from eukaryotes.

What are the three domains of life?

Bacteria, Archaea, Eukarya

Which domain includes traditional prokaryotes like E. coli?

Bacteria

Which domain consists of extremophiles that are distinct from bacteria?

Archaea

How are archaea and bacteria related compared to humans and bacteria?

Archaea and bacteria are as different from each other as humans are from bacteria.

What are the defining characteristics of bacteria?

Single-celled, lack a nucleus, found everywhere.

Give an example of a gut bacterium.

Escherichia coli (E. coli)

Name a bacterium that can cause infections.

Streptococcus

Where can Pseudomonas bacteria typically be found?

In soil and water

What was the original name for archaea?

Archaebacteria

Why was the term archaebacteria replaced with archaea?

Because archaea are significantly different from bacteria.

What type of environments do extremophiles thrive in?

High salt, acidity, or heat.

What are the three types of archaea based on metabolism?

Methanogens, halophiles, thermoacidophiles.

What gas do methanogens produce?

Methane (CH₄).

In what type of environment would you find halophiles?

Salty environments (e.g., the Dead Sea).

What extreme conditions do thermoacidophiles tolerate?

High temperatures and acidic conditions.

Are archaea more closely related to bacteria or eukaryotes?

Eukaryotes.

What does the phylogenetic tree suggest about archaea and eukaryotes?

They share a more recent common ancestor compared to bacteria.

Name two molecular features archaea share with eukaryotes.

Histone-like proteins and RNA polymerase.

What is the size of the smallest known cells (Mycoplasma)?

0.2–0.3 µm.

What is an example of a very large cell?

Neurons (up to 1+ meter in length).

Name three factors that limit cell size.

Surface area-to-volume ratio (SA:V), diffusion rates, and concentration requirements.

Why does diffusion become a problem in large cells?

Molecules take longer to reach all parts of the cell.

How does enzyme concentration affect cell function?

Cells need a high enough concentration of enzymes and reactants for efficient metabolism.

What is the typical size range for bacterial cells?

1–5 µm.

What is the typical size range for animal cells?

10–100 µm.

Why do larger cells struggle with nutrient and waste exchange?

Their volume increases faster than their surface area.

How do eukaryotic cells overcome size limitations?

By using organelles for compartmentalization.

How does surface area scale with cell length?

Surface area is proportional to length².

How does volume scale with cell length?

Volume is proportional to length³.

What happens to SA:V as a cell gets larger?

SA:V decreases.

What is one way cells increase SA:V without reducing size?

By developing microvilli.

Why do red blood cells have a flattened shape?

To maximize surface area for gas exchange.

How does breaking a large cube into smaller cubes affect total surface area?

It increases total surface area.

What happens to SA:V when a 20 µm cube is divided into 1,000 smaller 2 µm cubes?

It increases from 0.3 to 3.0.

Why do small cells have a metabolic advantage over large cells?

They have a higher SA:V, allowing faster nutrient and waste exchange.

What is the key takeaway from the SA:V demonstration?

Smaller cells maximize metabolic efficiency.

How does volume change when cell size doubles?

It increases by 8× (cube of length).

How does surface area change when cell size doubles?

It increases by 4× (square of length).

Why is a decreasing SA:V ratio problematic for large cells?

It limits the rate of nutrient uptake and waste removal.

What happens when a cell’s SA:V becomes too low?

The cell cannot sustain its metabolic demands.

What happens to SA:V when a large cube is divided into smaller cubes?

SA:V increases.

Does total volume change when a cube is divided into smaller cubes?

No, total volume remains constant.

Which has the highest SA:V ratio: a 20 µm cube, an 8 × 10 µm cube set, or a 1,000 × 2 µm cube set?

The 1,000 × 2 µm cubes.

Why do smaller cells exchange nutrients more efficiently?

They have a higher SA:V ratio.

What cell structure increases surface area without increasing volume?

Microvilli.

Where in the body are microvilli commonly found?

In the intestinal lining.

What is the main function of microvilli?

Maximizing nutrient absorption.

How do microvilli help maintain a high SA:V ratio?

They increase surface area while keeping volume constant.

What type of molecules diffuse the fastest?

Small molecules like O₂ and CO₂.

Why do large molecules diffuse slowly?

They have greater mass and encounter more resistance.

Why is diffusion alone not sufficient for large cells?

It is too slow for distributing macromolecules.

Name two ways eukaryotic cells compensate for slow diffusion.

Active transport and cytoplasmic streaming.

What protein helps move vesicles along microtubules?

Kinesin.

What process circulates cytoplasm in plant cells?

Cyclosis (cytoplasmic streaming).

Which organelle system transports proteins and lipids?

The endomembrane system (ER → Golgi → vesicles).

Why do reactions depend on reactant concentrations?

Molecules must collide frequently for reactions to occur.

Why do large cells struggle with maintaining high reactant concentrations?

A larger volume dilutes enzymes and reactants.

How do eukaryotic cells ensure efficient reactions?

They use compartmentalization (e.g., mitochondria for ATP production).

What is the main advantage of organelles in eukaryotic cells?

They localize reactants, increasing reaction efficiency.

What problem does compartmentalization solve in eukaryotic cells?

It helps maintain high concentrations of reactants and prevents interference between reactions.

What structures in eukaryotic cells enable compartmentalization?

Membrane-bound organelles.

Give an example of an organelle that enhances efficiency by isolating reactions.

Chloroplasts concentrate photosynthesis-related molecules.

How does compartmentalization benefit metabolism?

It localizes enzymes and substrates, increasing reaction efficiency.

What are the three domains of life?

Bacteria, Archaea, and Eukaryota.

Which domain(s) lack a nucleus?

Bacteria and Archaea.

What structural feature is unique to eukaryotes?

Membrane-bound organelles.

What type of cytoskeletal structures do prokaryotes have?

Simple filament systems (e.g., FtsZ for division).

Where is DNA stored in prokaryotic cells?

In the nucleoid (not membrane-bound).

How is DNA organized in eukaryotic cells?

Linear chromosomes with histones.

What internal membrane structures are found in eukaryotes but not prokaryotes?

Endoplasmic reticulum, Golgi complex, lysosomes, and mitochondria.

Do prokaryotes have a cytoskeleton?

Yes, but it is simpler than in eukaryotes.

What is the defining feature of eukaryotic cells?

The membrane-bound nucleus.

What is the function of nuclear pores?

They regulate transport of molecules between the nucleus and cytoplasm.

What is the nucleolus responsible for?

Synthesizing rRNA and assembling ribosomes.

How does the nucleus differ from a prokaryotic nucleoid?

The nucleus has a double membrane; the nucleoid does not.

What key structural feature is missing in prokaryotes?

A membrane-bound nucleus.

What organelle is always visible in eukaryotic cells under a microscope?

The nucleus.

What structure do both prokaryotic and eukaryotic cells share?

Ribosomes.

What is the function of the cell wall in prokaryotic cells?

Provides structural support and protection.

What organelle is responsible for protein and lipid synthesis?

The endoplasmic reticulum (ER).

What is the main function of the Golgi complex?

Modifying, packaging, and transporting proteins.

Which organelle produces ATP?

Mitochondria.

What is the function of lysosomes?

Digestion and breakdown of macromolecules.

Which organelle detoxifies harmful substances like hydrogen peroxide?

Peroxisomes.

What is the primary function of chloroplasts?

Photosynthesis in plants and algae.

What structure is unique to animal cells and helps with cell division?

Centrioles.

Where are free ribosomes located, and what do they do?

They are scattered in the cytoplasm and synthesize proteins that stay in the cell.

What is the function of the plasma membrane’s carbohydrate modifications?

Cell recognition and communication.

What role do peroxisomes play in metabolism?

They break down fatty acids and detoxify hydrogen peroxide via catalase.

What is the main function of the large central vacuole in plant cells?

Stores water, nutrients, and waste while maintaining turgor pressure.

What structure in plant cells connects adjacent cells for communication?

Plasmodesmata.

What is the function of the chloroplast’s grana?

They contain thylakoid membranes where photosynthesis occurs.

What is the tonoplast?

The membrane surrounding the central vacuole.

What cytoskeletal component is responsible for forming the mitotic spindle?

Microtubules.