Cell Biology: Prokaryotic and Eukaryotic Cell Structure and Function

Comprehensive practice flashcards covering animal cell organelles, membrane transport, bacterial cell wall chemistry (Gram-positive vs. Gram-negative), prokaryotic structures, morphology, endospores, and eukaryotic cellular components.

In an animal cell, which organelle receives proteins from the endoplasmic reticulum, processes them, and packages them into vesicles for export or cellular use?

Golgi apparatus (Golgi body)

Which membrane-bound organelles contain hydrolytic digestive enzymes responsible for breaking down cellular substances and foreign material?

Lysosomes

Through which cellular process does the eukaryotic nucleus divide to facilitate cell replication?

Mitosis

Which organelle is considered the primary site of cellular respiration and ATP production in eukaryotic cells?

Mitochondria

What are the three principal chemical components that constitute a membrane phospholipid molecule?

A glycerol backbone, two fatty acid chains, and a phosphate group linked to a polar head group such as choline

How do saturated fatty acid chains differ structurally from unsaturated fatty acid chains in lipid membranes?

Saturated fatty acid chains contain only single carbon-carbon bonds and are straight, whereas unsaturated fatty acid chains possess one or more double bonds that introduce kinks into the chain

Which classes of substances can move freely across the phospholipid bilayer without transport proteins?

Gases like $CO_2$ and $O_2$, hydrophobic molecules such as benzene, and small polar molecules such as $H_2O$ and ethanol

What is the definition of simple diffusion across a membrane?

The movement of molecules from an area of high concentration to an area of low concentration until dynamic equilibrium is reached

How is osmosis specifically defined regarding solute concentrations?

The movement of water or solvent across a semipermeable membrane from an area of low solute concentration to an area of high solute concentration

What are the two alternating carbohydrate derivatives shown here that form the glycan backbone of bacterial peptidoglycan?

N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

Which enzyme catalyzes the peptide cross-link in bacterial peptidoglycan by recognizing D-ala-D-ala as its substrate?

Transpeptidase (D,D-transpeptidase / penicillin-binding protein [PBP])

What two types of teichoic acids anchor the peptidoglycan wall in Gram-positive bacteria, and what does each attach to?

Wall Teichoic Acid (WTA), which links peptidoglycan sheets together, and Lipoteichoic Acid (LTA), which anchors the peptidoglycan sheets to the plasma membrane

What bacterial cell envelope structure is depicted in this 3D rendering, characterized by an outer membrane, a periplasmic space with a thin peptidoglycan layer, and an inner membrane?

Gram-negative cell wall

What three distinct structural sections comprise the lipopolysaccharide (LPS) molecule in Gram-negative bacteria?

Lipid A, core polysaccharide, and O-polysaccharide (O-antigen)

Which portion of lipopolysaccharide (LPS) acts as an endotoxin that triggers toxicity when cleaved by the innate immune system?

Lipid A

In Step 3 of the Gram staining procedure, what is the specific role of the iodine solution applied for $1\,\text{min}$?

It acts as a mordant to form an insoluble crystal violet-iodine complex within the peptidoglycan matrix

What effect does washing the slide with alcohol for $20\,\text{sec}$ have on Gram-negative cell walls during Gram staining?

The crystal violet-iodine complex is washed out of the thin peptidoglycan layer, leaving the Gram-negative cells colorless

Why does the counterstain safranin fail to change the purple appearance of Gram-positive bacteria during Step 5 of Gram staining?

The thick peptidoglycan cell wall retains the purple crystal violet-iodine complex, which masks the red safranin dye

What are the common bacterial shapes identified in microbiology?

Coccus (spherical), bacillus (rod), coccobacillus (oval rod), vibrio (curved rod), spirillum (rigid spiral), and spirochete (flexible spiral)

Which specific arrangement of spherical bacterial cells is circled in this diagram?

Staphylococci

Which specific arrangement of spherical bacterial cells is circled in this diagram?

Streptococci

What arrangement describes rod-shaped bacteria aligned side-by-side in a fence-like cluster?

Palisades

How do a bacterial capsule and a slime layer differ structurally and functionally?

A capsule is organized, firmly attached, and protects against phagocytosis and dehydration while aiding biofilm adherence; a slime layer is unorganized, loosely attached, and easily removed

What rotational directions do bacterial flagella employ to produce motility, and what movement pattern results?

They rotate clockwise and counterclockwise to produce an alternating running and tumbling movement pattern

How do bacterial fimbriae differ in size, distribution, and primary function compared to flagella?

Fimbriae are shorter, thinner hair-like appendages that cover the cell surface or cluster at poles to mediate surface attachment rather than motility

In this transmission electron micrograph of two interacting bacteria, which tubular surface structure connects the cells for genetic exchange?

Sex pilus (pilus)

What are the structural features of the bacterial chromosome located within the nucleoid?

A single, long, circular DNA double helix that contains all genes essential for structural and functional processes and lacks a surrounding membrane

What are bacterial plasmids, and what types of non-essential genes do they typically carry?

Small, circular, double-stranded extrachromosomal DNA elements that replicate independently and carry $5\text{–}100$ genes encoding traits such as antibiotic resistance, toxin production, or heavy metal tolerance

What is the sedimentation coefficient of a prokaryotic ribosome, and what two subunits form it?

A $70S$ ribosome composed of a $50S$ large subunit and a $30S$ small subunit

What rRNA molecules and protein counts make up the prokaryotic $50S$ and $30S$ ribosomal subunits?

The $50S$ subunit contains $23S$ rRNA ($2900\,\text{bases}$), $5S$ rRNA ($120\,\text{bases}$), and $31$ proteins; the $30S$ subunit contains $16S$ rRNA ($1540\,\text{bases}$) and $21$ proteins

What highly resistant, dehydrated bacterial survival structure is shown within the parent cell in this electron micrograph?

Endospore

What environmental hazards can bacterial endospores withstand during dormancy?

Extreme heat, dehydration, toxic chemicals, and radiation

What are the typical size ranges for prokaryotic cells versus eukaryotic cells?

Prokaryotic cells typically measure $1\text{–}5\,\mu m$ in diameter, whereas eukaryotic cells typically measure $10\text{–}100\,\mu m$ in diameter

What polysaccharides form the cell walls of plants, algae, and fungi, and what bacterial component do they all lack?

Plant and algal walls contain cellulose (with pectin in plants), and fungal walls contain chitin and glucans; eukaryotic cell walls do not contain peptidoglycan

Based on this micrograph, how do the flagella of Euglena (left) compare in length and abundance to the cilia of Tetrahymena (right)?

Flagella are few in number and long relative to cell size, while cilia are short and numerous over the entire cell surface

How do eukaryotic flagella and cilia differ in their mechanical pattern of motion?

Flagella move in an undulating, propeller-like wavelike pattern, whereas cilia exhibit a coordinated back-and-forth beating motion

What are the primary molecular constituents and biological functions of the eukaryotic glycocalyx?

It consists of carbohydrates, glycoproteins, and glycolipids; it strengthens the cell surface, anchors adjacent cells together, and participates in cell-cell recognition

What three distinct mechanisms of eukaryotic endocytosis are shown from left to right in this illustration?

Phagocytosis (cellular eating of solid particles into phagosomes), pinocytosis (cellular drinking of extracellular fluid into vesicles), and receptor-mediated endocytosis (internalization via coated pits and vesicles)

What is cytoplasmic streaming in eukaryotic cells?

The active, coordinated movement and flowing of cytoplasm from one part of the cell to another, mediated by the cytoskeleton

What is the structural definition of chromatin within the eukaryotic nucleus?

Genomic DNA wrapped around histone proteins

What is the functional purpose of nuclear pores embedded within the nuclear envelope?

They control and regulate the selective transport of molecules between the interior of the nucleus and the cytoplasm

What internal structural elements characterize a mitochondrion?

An outer membrane, a folded inner membrane arranged into cristae to maximize surface area, and an internal fluid-filled matrix

According to this comparative diagram, what are the overall sedimentation coefficients and subunit compositions of prokaryotic versus eukaryotic (mammalian) ribosomes?

Prokaryotic ribosomes are $70S$ (composed of $50S$ and $30S$ subunits), while eukaryotic ribosomes are $80S$ (composed of $60S$ and $40S$ subunits)

What rRNA strands and protein quantities comprise the mammalian eukaryotic $60S$ and $40S$ ribosomal subunits?

The $60S$ subunit contains $28S$ ($4800\,\text{bases}$), $5.8S$ ($160\,\text{bases}$), and $5S$ ($120\,\text{bases}$) rRNAs with $50$ proteins; the $40S$ subunit contains $18S$ rRNA ($1900\,\text{bases}$) with $33$ proteins

How do the rough endoplasmic reticulum and smooth endoplasmic reticulum differ in structure and metabolic specialization?

Rough ER is studded with ribosomes and synthesizes proteins while carrying out post-translational modifications like glycosylation; smooth ER lacks ribosomes and synthesizes phospholipids, fats, and steroids

What sequential pathway of protein trafficking and secretion is depicted in this diagram?

Proteins synthesized in the rough endoplasmic reticulum enter transport vesicles, travel to the cis face of the Golgi apparatus, pass through Golgi cisternae to the trans face for modification, and exit via secretory vesicles that fuse with the cell membrane

How do peroxisomes differ functionally from lysosomes?

Lysosomes originate from the Golgi complex and use digestive enzymes to degrade bacteria and waste; peroxisomes contain oxidative enzymes to modify organic substances, break down fatty acids, and convert toxic hydrogen peroxide ($H_2O_2$)