quiz 4 BIO 101

Topic 1: Cells Basics and Size scales

What is the basic unit of structure and function in an organism?

The cell.

Give an example of a unicellular protist shown in Figure 4.01.01.

A paramecium (labeled as a unicellular protist).

Why are most cells too small to be seen by the unaided eye?

Scientists must use microscopes to observe them because they fall below the resolution limit of the human naked eye.

According to the cell size range, what are the relative size categories of most plant and animal cells?

Between 10 um and 100 um.

According to the cell size range, what are the relative size categories of most bacteria?

Between 1 um and 10 um.

Topic 2: Microscopy Parameters & Light Microscopes (LMs)

How does a Light Microscope (LM)
work?

Visible light is passed through a specimen and then through glass lenses, which refract (bend) the light to magnify the image.

What are the three important parameters in microscopy?

1. Magnification

2. Resolution

3. Contrast

Define Magnification.

The ratio of an object's image size to its real size.

Define Resolution.

The measure of the clarity of the image, or the minimum distance between two distinguishable points.

Define Contrast.

The difference in brightness between the light and dark areas of the image.

What is the effective magnification limit of a standard Light Microscope (LM)?

Up to about 1,000 times the size of the actual specimen.

What is used to enhance contrast and enable cell components to be stained or labeled in LMs?

Various staining techniques and fluorescent markers.

Why are most subcellular structures (organelles) unable to be resolved by light microscopy?

They are too small to meet the resolution limits of light microscopes.

• Topic 3: Electron Microscopes (EMs) &

Advanced Techniques

What do Electron Microscopes (EMs) use to image specimens instead of light?

A focused beam of electrons.

What is the primary function of a Scanning Electron Microscope (SEM)?

To focus electrons onto the surface of a specimen, producing detailed three-dimensional (3D) images.

What is the primary function of a Transmission Electron Microscope (TEM)?

To focus electrons through a specimen to study the internal structure of cells

What is Cryo-electron microscopy (cryo-E.M)?

A technique that preserves specimens at extremely low temperatures, allowing visualization of structures in their natural cellular environment.

Topic 4: Cell Fractionation

What is Cell Fractionation?

A process that breaks up cells and separates their components using several rounds of centrifugation.

On what basis do cell components separate during cell fractionation?

Based on their relative size.

What is the main objective of cell fractionation for scientists?

To determine the functions of specific organelles.

Which two scientific fields complement each other to correlate cell function with structure?

Biochemistry and cytology.

Topic 5: Prokaryotic vs. Eukaryotic Cells

What are the four basic features shared by all cells?

1. Plasma membrane

2. Semifuid substance called cytosol

3. Chromosomes (carry genes)

4. Ribosomes (make proteins)

Which domains of life consist of prokaryotic cells?

Bacteria and Archaea.

Which groups of organisms consist of eukaryotic cells?

Protists, fungi, animals, and plants.

Where is the DNA located in a eukaryotic cell?

Inside the nucleus, an organelle bounded by a double membrane.

What are three defining characteristics of prokaryotic cells?

1. No nucleus

2. DNA is in an unbound region called the nucleoid

3. No membrane-bound organelles

What region contains the cytoplasm in both prokaryotic and eukaryotic cells?

The region bound by the plasma membrane.

Topic 6: Prokaryotic Cell Structures (Figure

4.4)

Name three external structures that can be found on a typical rod-shaped bacterium.

Fimbriae, Glycocalyx, and Flagella.

What is the function of the flagella in a bacterium?

Locomotion (movement/propulsion).

What are the three layers protecting/enclosing a bacterium from the inside out?

1. Plasma membrane

2. Cell wall

3. Glycocalyx (outer coating)

Topic 7: Surface Area-to-Volume

Relationships

What are the typical diameter ranges for bacteria vs. eukaryotic cells?

Bacteria are 1-5 um, while eukaryotic cells are 10-100 um.

Why is the ratio of surface area to volume critical for a cell?

The plasma membrane only allows a limited amount of a substance to cross per second to service the entire cell volume.

As a cell increases in size, how do its surface area and volume scale differently?

Surface area increases proportional to the square of its linear dimension, whereas volume increases proportional to the cube.

Do smaller cells or larger cells have a greater surface area-to-volume ratio?

Small cells have a greater ratio.

Topic 8: Membrane Structure &

Compartmentalization

What is the basic fabric of most biological membranes?

A double layer of phospholipids (phospholipid bilayer) and other lipids.

Describe the two regional properties of a phospholipid molecule in the membrane.

A hydrophilic region (facing the water inside/outside) and a hydrophobic region (facing inward).

How do eukaryotic cells accommodate their large size to perform metabolism efficiently?

They have extensive internal membranes that divide the cell into compartments (organelles).

Topic 9: Animal vs. Plant Cell Structures

(Figure 4.7)

Name three structures labeled in the plant cell diagram that are typical of plants but not animals.

Cell wall, Chloroplast, and Central vacuole (or Plasmodesmata).

Name a motility structure shown in the animal cell diagram but absent in the plant diagram.

Flagellum.

What are the three components that make up the cell's cytoskeleton?

Microfilaments, Intermediate filaments, and Microtubules.

Topic 10: The Nucleus & Genetic Instructions

What structure maintains the mechanical shape of the nucleus?

The nuclear lamina, which is composed of protein filaments.

What is chromatin?

The complex of DNA and proteins making up chromosomes.

What is the specific function of the nucleolus?

It is the site of ribosomal RNA (rRNA) synthesis.

What structure encloses the nucleus to separate it from the cytoplasm?

The nuclear envelope, which is a double membrane consisting of two lipid bilayers.

What is the function of nuclear pores?

They regulate the entry and exit of macromolecules and particles.

Topic 11: Ribosomes (Protein Factories)

What are ribosomes composed of?

Complexes of ribosomal RNA (rRNA) and protein.

True or False: Ribosomes are considered membrane-bound organelles.

They are structural complexes, not membrane-bound organelles.

What are the two locations where ribosomes carry out protein synthesis?

1. In the cytosol (free ribosomes)

2. On the outside of the endoplasmic reticulum or nuclear envelope (bound ribosomes)

What are the two structural subunits that make up a functional ribosome?

The large subunit and the small subunit.

Topic 12: The Endomembrane System Overview

What are the six primary components of the endomembrane system?

1. Nuclear envelope

2. Endoplasmic reticulum (ER)

3. Golgi apparatus

4. Lysosomes

5. Vesicles and vacuoles

6. Plasma membrane

How are the components of the endomembrane system related to each other?

They are either continuous or connected through transfer by vesicles.

Which organelle accounts for more than half of the total membrane in many eukaryotic cells?

The endoplasmic reticulum (ER).

Topic 13: Endoplasmic Reticulum (ER) Functions

What are the two distinct regions of the Endoplasmic Reticulum?

Smooth ER (lacks ribosomes) and Rough ER (studded with ribosomes).

What are the four primary functions of the Smooth ER?

1. Synthesizes lipids

2. Metabolizes carbohydrates

3. Detoxifies drugs and poisons

4. Stores calcium ions

What are glycoproteins, which are secreted by the Rough ER?

Proteins covalently bonded to carbohydrates.

What does the Rough ER distribute to transport proteins throughout the cell?

Transport vesicles (proteins surrounded by membranes).

Why is the Rough ER considered a
"factory" for the cell?

It functions as a membrane factory for the cell.

Topic 14: The Golgi Apparatus

What structural components make up the Golgi apparatus?

Flattened membranous sacs called cisternae.

What are the three primary functions of the Golgi apparatus?

1. Modifies and stores products of the ER

2. Manufactures some macromolecules

3. Sorts and packages materials into transport vesicles

What are the two distinct faces of a Golgi apparatus stack?

The cis face ("receiving" side near the ER) and the trans face ("shipping" side).

What acts like "zip codes" to aid in sorting Golgi products?

Molecular identification tags, such as phosphate groups.

Topic 15: Lysosomes & Cellular Digestion

What is a lysosome?

A membranous sac of hydrolytic enzymes that can digest macromolecules.

In what type of environment do lysosomal enzymes work best?

An acidic environment inside the lysosome.

Define phagocytosis as carried out by lysosomes.

A process where a cell engulfs another cell or food particle, forming a food vacuole for digestion.

Define autophagy as carried out by lysosomes.

A recycling process where lysosomes use enzymes to break down and recycle the cell's own damaged organelles and macromolecules.

Topic 16: Vacuoles

From which two major organelles are vacuoles derived?

The endoplasmic reticulum and Golgi apparatus.

What is the function of contractile vacuoles found in many freshwater protists?

They pump excess water out of cells.

What is the function of a central vacuole in mature plant cells?

It serves as a repository for inorganic ions (including potassium and chloride) and helps with cell growth.

Topic 17: Energy-Converting Organelles Overview

What is the primary function of mitochondria?

They are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP by breaking down sugars and fats.

What is the primary function of chloroplasts?

They are the sites of photosynthesis, using solar energy to synthesize organic compounds (sugars) from carbon dioxide and water.

What are peroxisomes?

They are oxidative organelles involved in metabolic processes.

Topic 18: The Endosymbiont Theory

Explain the basis of the endosymbiont theory.

An early ancestor of eukaryotic cells engulfed an oxygen-using, nonphotosynthetic prokaryotic cell, forming a symbiotic relationship that eventually merged into a single organism with a mitochondrion.

According to the theory, how did photosynthetic eukaryotes evolve?

A eukaryotic cell containing a mitochondrion engulfed a photosynthetic prokaryote, which became the ancestor of cells containing chloroplasts.

What three lines of structural evidence support the endosymbiont theory?

1. Enveloped by a double membrane

2. Contain ribosomes and multiple circular
   DNA molecules

3. Grow and reproduce somewhat independently in cells

Topic 19: Mitochondria Structure

What are cristae?

Infoldings of the inner membrane of a mitochondrion.

Why is the surface area of cristae biologically important?

It presents a large surface area for enzymes that synthesize ATP.

What two internal compartments are created by the inner mitochondrial membrane?

The intermembrane space and the mitochondrial matrix.

Where are some metabolic steps of cellular respiration catalyzed?

In the mitochondrial matrix.

Topic 20: Chloroplast Structure

What green pigment do chloroplasts contain?

Chlorophyll.

What are thylakoids?

Flattened, membranous sacs inside the chloroplast that are stacked to form a granum.