lecture 7: intro to cells

Question 1

What is the basic Cell Theory?

Answer 1

1. All organisms are made of one or more cells
2. Cell = basic unit of life
3. All cells come from preexisting cells

Question 2

What is a cell and how is its structure?

Answer 2

• Simplest collection of matter that can live
• Fundamental unit of structure, function, and reproduction of organisms
• All organisms are composed of one or more cells
• Cells make up tissues & organs
• Cell structure is diverse (different shapes and sizes) and correlates to its function

Question 3

What are the 4 main types of tissues in vertebrate animals?

Answer 3

1. Nervous
2. Muscle
3. Epithelial
4. Connective

Question 4

How big are eukaryotic and prokaryotic cells?

Answer 4

Cells = 1-100 micrometers (um)
Prokaryotic = 1-10 um
Eukaryotic = 10-100 um

Question 5

What is microscopy?

Answer 5

Essential tool to study cell structure and other aspects of its biology

Question 6

What is magnification?

Answer 6

Ratio of an object’s image to its real size (4X, 10X, 40X…)

Question 7

What is resolution?

Answer 7

Ability to observe two nearby objects as being distinct form one another (in nm)

Question 8

What is constrast and how do you increase it?

Answer 8

• How well an object stands out from its surroundings.

- Can be increased in stains and florescent tags

Question 9

What are the 4 important parameters in microscopy?

Answer 9

1. Magnification
2. Resolution
3. Contrast
4. 2D vs 3D image

Question 10

What is the main difference between a light and an electron microscope?

Answer 10

Electron microscope has higher magnification and resolution.

Question 11

What are the 5 shared features in all cells?

Answer 11

1. Plasma membrane
2. Chromosomes
3. Cytoplasm
4. Ribosomes
5. Cytoskeleton

Question 12

What are the 2 majors types of cells and its categories?

Answer 12

1. Prokaryotic (unicellular): Bacteria and Archaea

2. Eukaryotic (uni/multicellular): Animals, Plants, Fungi, Protists

Question 13

What is the 2 main differences between a prokaryotic cell and an eukaryotic cell?

Answer 13

Eukaryotic is 1.larger and 2.more complex

Question 14

Do larger organisms have larger cells than smaller organisms?

Answer 14

No, they just have more cells.

Question 15

What is one reason why cell size is limited?

Answer 15

Volume of cell increases faster than the surface area —> acquiring nutrients & elimination of waster become harder —> needs more and more nutrients, but can not keep up with transport of nutrients and wastes as they are transported in and out of the cell via the cell membrane/surface area

Question 16

What are the 2 ways eukaryotic cell adapts to the SA:V problem?

Answer 16

1. Using microvilli (long, thin projections) to increase cell surface wthout significantly increasing the volume
2. Decreasing active cell volume: in plant cells, large central vacuole = metabolically dead, so no need for nutrients and do not produce waste

Question 17

2 main components of plasma membrane structure?

Answer 17

1. Phospholipid that forms bilayer

2. Membrane-bound proteins with various functions

Question 18

What are the 2 functions of plasma membrane and how are they accomplished?

Answer 18

1. Selectively permeable barrier: regulates materials in and out cell (homeostasis)
   - Accomplished by phospholipid bilayer and transport proteins
2. Cell joining & cell communication
   - Accomplished by proteins in membrane

Question 19

Which 2 characteristics influence a chemical’s permeability? (from plasma membrane)

Answer 19

1. Size: smaller is better
2. Polarity (hydrophobic vs hydrophillic): nonpolar/hydrophobic is better
   * it is a mix of both*

Question 20

How do phospholipids contribute to the selectively permeable barrier?

Answer 20

Prevent mid/large polar molecules and ions from crossing the membrane

Question 21

How do transport proteins contribute to the selectively permeable barrier?

Answer 21

Facilitate transport of certain polar molecules and ions

Question 22

What are viruses?

Answer 22

Very small (20-300 nanometers nm) and abundant infectious particles consisting of nucleic acid genome + outer covering

Question 23

How can a virus be considered “alive”?

Answer 23

Must enter host cell & use host’s biosynthetic machinery to reproduce and synthesize its proteins —> viruses = obligate intracellular parasites

Question 24

How do viruses work?

Answer 24

Each type of virus infects specific unicellular species/cell type in a multicellular species —> viruses are specific for each target

• “Disguise” and trick cells to make think that they need them
  1. Virus enter host cell
  2. Replicate itself
  3. Transcription and manufacture of capsid proteins
  4. New virus particles exit cell
• new virus particles are self-assembled*

Question 25

Why do biologists study viruses (2 reasons)?

Answer 25

• Because they cause disease and some, cancer.

- Because virtually every system, tissue, and cell can be infected by at least one kind of virus

Question 26

Virus structure?

Answer 26

Composed of a protein shell called capsid that encloses the viral genome
- Capsid = built from protein subunits called capsomeres

Question 27

How do viruses differ (2)?

Answer 27

Wide variety of shapes (can be identified by shape alone)

1. Non-enveloped vs Enveloped
2. Viral genomes = either DNA or RNA viruses (double or single-stranded)