CH. 4 Introduction to Cell Structure and Microscopy

Chapter 4

What is the primary function of the lens in a light microscope?

It alters and refracts light passing through a specimen to make the image appear larger.

What is the difference between magnification and resolution?

Magnification is making an image larger, whereas resolution is the ability to distinguish distinct points clearly to clarify the image.

What is the practical magnification limit for a standard light microscope?

About $1,000 \times$ the original size of the specimen.

How does a Scanning Electron Microscope (SEM) produce an image of a specimen?

It scans the surface by bouncing electrons off of the specimen.

How does a Transmission Electron Microscope (TEM) visualize internal cell structures?

It transmits electrons through a thin sample, similar to how light passes through a specimen in a light microscope.

What are the four basic characteristics shared by all cells?

A plasma membrane, cytoplasm (with cytosol), DNA, and ribosomes.

Which two domains of life consist of prokaryotic cells?

Bacteria and Archaea.

Where is DNA located inside a prokaryotic cell?

In an un-enclosed central region called the nucleoid.

Why are individual prokaryotic cells restricted to small sizes?

They rely partially on passive diffusion to move materials, which requires a high surface area to volume ratio to remain efficient.

How do prokaryotes grow as a population without increasing individual cell volume?

They form colonies composed of many small, individual cells growing together.

What peptidoglycan-containing structure is located outside the plasma membrane in most prokaryotes?

The cell wall.

How does the eukaryotic cytoskeleton assist large cells with transport?

It maintains cell shape and acts as internal tracks or railways for active transport of materials.

Why does the nucleus appear as a dense, dark spot under a microscope?

It is tightly packed with a large quantity of DNA, which makes it hard for light to pass through.

How many base pairs of DNA are contained within a single haploid eukaryotic nucleus?

$3 \times 10^9$ base pairs ($3\text{ billion}$ base pairs).

What is the structural setup of the nuclear envelope?

It consists of two plasma membranes (four individual sheets of phospholipids) containing nuclear pores to regulate traffic.

What function takes place inside the nucleolus?

Ribosomal RNA (rRNA) and proteins assemble to form ribosomal subunits.

What proteins does DNA wrap around to package itself into chromatin?

Histones.

In which two main locations are ribosomes found in eukaryotic cells?

Floating free in the cytosol, and attached to the rough endoplasmic reticulum (rough ER) or nuclear envelope.

What is the primary function of mitochondria?

They carry out cellular respiration to convert energy into ATP.

What are cristae, and what role do they play in mitochondria?

They are folds of the inner mitochondrial membrane that increase surface area for ATP production.

What is the main function of peroxisomes?

They break down fatty acids and amino acids, and detoxify harmful substances within the cell.

Which three cell structures are characteristic of plant cells but absent in animal cells?

Chloroplasts, a cell wall, and a large central vacuole.

What organic polymer forms the main structural component of plant cell walls?

Cellulose, which is a polymer of glucose.

What is stored inside the central vacuole of a plant cell?

Primarily water, along with stored sugars, proteins, amino acids, and nucleic acids.

Which organelle contains hydrolytic enzymes to break down molecules in animal cells?

Lysosomes.