Chapter 4: Cell Structure

Quiz-style Q&A flashcards covering key concepts from Chapter 4: Cell Structure, including microscopy, cell theory, cell types, organelles, endomembrane system, cytoskeleton, and cell communication.

What is the smallest unit of life that makes up all organisms?

A cell.

What does the unified cell theory state?

One or more cells comprise all organisms; the cell is the basic unit of life; new cells arise from existing cells.

What are the two main types of microscopes used to study cells, and which provides higher magnification and resolution?

Light microscopy and electron microscopy; electron microscopy provides higher magnification and resolving power.

Approximately how large is a typical human red blood cell in diameter?

About 8 micrometers (μm).

What is resolving power in microscopy?

The ability to distinguish two adjacent structures as separate; higher resolution yields clearer detail.

Why are most cell components not easily visible with standard light microscopes?

Most cells are transparent; staining often kills cells, and basic light microscopy has limited resolution.

What is the difference between a light microscope and an electron microscope in terms of what they use to form images?

Light microscopes use visible light; electron microscopes use beams of electrons.

What are the two main types of electron microscopes and what does each reveal?

Scanning electron microscope (SEM) reveals surface details; transmission electron microscope (TEM) reveals internal structures.

Which domains include prokaryotes and which include eukaryotes?

Prokaryotes: Bacteria and Archaea; Eukaryotes: animals, plants, fungi, and protists.

What are the four common components shared by all cells?

Plasma membrane, cytoplasm, DNA, and ribosomes.

Where is prokaryotic DNA located?

In the nucleoid, a region in the cytoplasm not bounded by a membrane.

What is the typical size range for prokaryotic cells?

0.1 to 5.0 μm in diameter.

What are the roles of the bacterial cell wall and the capsule?

The cell wall provides shape and protection; the capsule aids attachment to surfaces and can help defend against the environment.

What is the major component of the plant cell wall?

Cellulose.

Why are mitochondria and chloroplasts often discussed together in the context of endosymbiosis?

Both contain their own DNA and ribosomes and are thought to have originated from endosymbiotic bacteria.

What is the function of mitochondria?

ATP production via cellular respiration; they have cristae and a matrix and own DNA/ribosomes.

What is the function of chloroplasts?

Carry out photosynthesis; contain chlorophyll; have thylakoids (grana) and stroma; possess own DNA and ribosomes.

What is the endomembrane system?

A group of membranes and organelles within eukaryotic cells that modify, package, and transport lipids and proteins; includes the nuclear envelope, ER, Golgi, lysosomes, and vesicles.

What is the difference between rough and smooth endoplasmic reticulum (ER)?

Rough ER has ribosomes and synthesizes/modifies proteins and phospholipids; smooth ER lacks ribosomes and synthesizes lipids, carbohydrates, detoxifies, and stores calcium.

What is the Golgi apparatus responsible for?

Sorting, tagging, packaging, and distributing lipids and proteins; cis face receives from ER; trans face ships; in plants it also synthesizes certain polysaccharides.

What are lysosomes?

Digest macromolecules, recycle worn-out organelles, and destroy pathogens; contain acid hydrolases.

What are peroxisomes and what do they do?

Oxidize fatty acids and amino acids; detoxify poisons; break down hydrogen peroxide; glyoxysomes in plants convert fats to sugars.

What are vesicles and vacuoles?

Membrane-bound sacs for storage and transport; vacuoles are generally larger, vesicles can fuse with membranes.

What is the central vacuole and its role in plant cells?

A large organelle that regulates water, maintains turgor pressure, and supports cell growth and expansion.

What are the three components of the cytoskeleton and their general roles?

Microfilaments (movement and shape), intermediate filaments (tension and anchoring), microtubules (resist compression and act as tracks for transport and chromosome movement).

What are microfilaments and what is their building block?

Actin filaments; they are the narrowest cytoskeletal elements and are involved in movement and shape.

What are intermediate filaments and their main role?

Filaments that bear tension and anchor organelles and the nucleus in place; provide structural support.

What are microtubules and their key functions?

Hollow tubes that resist compression, serve as tracks for vesicle movement, help pull chromosomes during division, and form centrioles, flagella, and cilia.

What is the 9+2 arrangement in flagella and cilia?

A ring of nine microtubule doublets around a central pair (9+2 structure).

What is the centrosome and what is notable about its presence in plant vs animal cells?

A microtubule-organizing center in animal cells containing two centrioles; plants typically lack a centrosome.

Which cells typically have lysosomes and a centrosome, and which often lack them?

Animal cells typically have lysosomes and a centrosome; many plant cells lack centrosomes and rely on other structures.

What structures are unique to plant cells compared with animal cells?

Cell wall, chloroplasts, and a large central vacuole.

What are plasmodesmata?

Channels through plant cell walls that connect adjacent plant cells’ cytoplasm for transport.

What are tight junctions?

Watertight seals between adjacent animal cells that prevent leakage.

What are desmosomes?

Spot welds between epithelial cells that link to intermediate filaments and help form strong sheets.

What are gap junctions?

Channels formed by connexons that connect adjacent animal cells, allowing ions and small molecules to pass; important in cardiac tissue.

What is the extracellular matrix (ECM) and what is collagen’s role within it?

A network of proteins and carbohydrates that holds tissues together and facilitates cell communication; collagen is the most abundant ECM protein.

How does ECM signaling typically start when a matrix molecule binds a cell-surface receptor?

Binding changes the receptor’s conformation, which alters intracellular signals via the cytoskeleton and can regulate gene transcription.

What is chromatin and how does it relate to chromosomes?

Chromatin is the DNA-protein complex in the nucleus; chromosomes are the condensed form of chromatin visible during cell division.

What is the nucleolus and its function?

A region within the nucleus where ribosomal RNA is synthesized and ribosomal subunits are assembled.

What is the nucleus and what does its envelope contain?

The organelle that houses DNA and directs ribosome and protein synthesis; enclosed by a nuclear envelope with nuclear pores.

What is the nuclear envelope and why is it significant?

A double-membrane boundary that regulates transport into and out of the nucleus and is continuous with the ER.

What is endosymbiosis and which organelles are explained by this theory?

A mutually beneficial relationship where one organism lives inside another; explains the origin of mitochondria and chloroplasts.

What evidence supports the endosymbiotic origin of mitochondria and chloroplasts?

They contain their own DNA and ribosomes, are similar in size to bacteria, and have double membranes.

Why is the plant cell’s central vacuole important for turgor and growth?

It stores water and regulates cell turgor, allowing the cell to expand without cytoplasmic synthesis.

What is the difference between the plant and animal plasma membranes regarding microvilli?

Plasma membranes can fold into microvilli in absorptive cells (e.g., intestinal lining) to increase surface area; more in absorptive tissues.

Why do plant cells have chloroplasts and animal cells do not?

Chloroplasts perform photosynthesis in plants (autotrophs); animals obtain energy by consuming organic molecules.