Module 1

Question 1

What is a cell?

Answer 1

The basic structural and functional units of every organism.

Question 2

What are the types of cells?

Answer 2

Prokaryotic & Eukaryotic

Question 3

What organisms consist of eukaryotic cells?

Answer 3

All organisms of the domain Eukarya - protists, fungi, animals, and plants.

Question 4

What does Protist refer to?

Answer 4

It’s an INFORMAL term that refers to a diverse group of mostly unicellular eukaryotes.

Question 5

What are the basic features of all cells?

Answer 5

Plasma/Cell Membrane

Cytosol; a jellylike semifluid, in which sub-cellular components are suspended

Chromosomes - carry genes in the form of DNA

Ribosomes - tiny complexes that make proteins according to instructions from the genes

Question 6

What are the major differences between Eukaryotic cells & Prokaryotic cells?

Answer 6

1. The location of their DNA.
   Eukaryotic cells store most of their DNA in the nucleus.
   In Prokaryotic cells most of the DNA is concentrated in the
   nucleoid.
2. Prokaryotic cell’s structure is much simpler due to their lack of a
   true nucleus and other membrane-enclosed organelles.
3. Eukaryotic cells are generally much larger than prokaryotic cells.
   The logistics of carrying out cellular metabolism sets limits on cell
   size. Smallest known cells are mycoplasmas (diameter 0.1-1µm),
   bacteria 1-5µm diameter, Eukaryotes 10-100µm diameter.
   As cells increase in size its surface area grows proportionally less
   than its volume, imposing an upper limit on size that is practical for
   metabolic requirements (due to plasma membrane). Larger
   organisms have more cells instead of larger cells.

Question 6

What domains are included in Prokaryotic cells?

Answer 6

Bacteria & Archaea; general cell structure of these domains are quite similar.

Question 7

What is a nucleus?

Answer 7

An organelle that contains most of the genes in eukaryotic cells. Some genes are located in mitochondria and chloroplasts.

Averages about 5µm in diameter.

Has a nuclear envelope.

Question 7

What is a nucleoid?

Answer 7

A region that is not membrane-enclosed where DNA is concentrated in Prokaryotic cells.

Question 8

What is the plasma membrane?

Answer 8

A selective barrier that allows the passage of oxygen, nutrients and waste to service the entire cell.

For each square micrometre of membrane, only a limited amount of a particular substance can cross per second, so the ratio of surface area to volume is critical.

Question 9

What is the phospholipid bilayer?

Answer 9

Is what the plasma membrane and the membrane of organelles consist of.

It is a double layer (bilayer) of phospholipids with various proteins attached to or embedded in it.

The hydrophobic parts of phospholipids and membrane proteins are found in the interior of the membrane.

Hydrophilic parts are in contact with aqueous solutions on either side.

Carbohydrate side chains may be attached to proteins or lipids on the outer surface of the plasma membrane.

Question 10

What do microvilli do?

Answer 10

Long, thin projections from a cell’s surface that increase surface area without an appreciable increase in volume.

This allows for a higher ratio of surface area to volume, which is important for cells that exchange a lot of material with their surroundings.

Question 11

Why does a eukaryotic cell have internal membranes?

Answer 11

They divide the cell into compartments which house organelles. The cell’s compartments provide different local environments that support specific metabolic functions, so incompatible processes can occur simultaneously in a single cell.

The plasma membrane and organelle membranes also participate directly in the cell’s metabolism because many enzymes are built right into the membranes.

Question 12

Are all membranes the same?

Answer 12

No.

While the basic structure of most membranes is a phospholipid bilayer, each membrane has a unique combination of lipids and proteins embedded in the bilayer suited to that membrane’s specific function.

Question 13

What are chromosomes and where are they found?

Answer 13

Found in the nucleus and appear as a mass of chromatin (DNA and associated proteins). Participates in ribosome synthesis.

Question 14

What is the nuclear envelope?

Answer 14

Is a double membrane, each a lipid bilayer with associated proteins which encloses the nucleus, separating its contents from the cytoplasm. The membranes are separated by a space of 20-40nm.

The envelope is perforated by pore structures that are about 100 nm in diameter. At the lip of each pore, the inner and outer membranes of the nuclear envelope are continuous.

An intricate protein structure called a pore complex lines each pore and plays an important role in the cell by regulating the entry and exit of proteins and RNAs, as well as large complexes of macromolecules.

Except at the pores, the nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments (in animal cells, called intermediate filaments) that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.

There is also much evidence for a nuclear matrix, a framework of protein fibres extending throughout the nuclear interior. The nuclear lamina and matrix may help organise the genetic material so it functions efficiently

Question 15

What characteristics enable prokaryotes to reach huge population sizes and thrive in diverse environments?

Answer 15

1. Populations can grow to be huge due to SMALL SIZE and RAPID REPRODUCTION.
2. Due to large populations MUTATIONS produce high genetic diversity, enabling rapid evolution.
3. DIVERSE ADAPTATIONS enable prokaryotes to live in a wide range of environments.
4. RAPID EVOLUTION results in diverse metabolic and structural adaptions.

Question 16

Are prokaryotes or eukaryotes more abundant in earth?

Answer 16

Prokaryotes.

Question 17

What is a prokaryote?

Answer 17

A single-celled (unicellular) organism, that thrive in an extreme range of environments