Unit 3: Cellular Level of Organization

Question 1

What is the cell?

Answer 1

The basic structural and functional unit of the body (can perform all basic life functions)

Question 2

What are the 3 principle parts of the cell?

Answer 2

1. Cell Membrane/Plasma Membrane/Plasmalemma
2. Cytoplasm
3. Nucleus

Question 3

What is (1) the cell/plasma membrane/plasmalemma and what is it composed of?

Answer 3

• = the boundary btw. the inside and outside of the cell
• composed of:
  
  1. Phospholipid bilayer
  2. Cholesterol
  3. Membrane proteins (2 types)
  4. Membrane carbohydrates
  5. Microvilli
• 1) and 3) = Fluid Mosaic Model of the cell membrane:
  
  • fluid - membrane constituents can move around
    (phospholipids and some proteins)
  • mosaic - proteins dot surface like tiles in a mosaic

Question 4

Info about the phospholipid bilayer

Answer 4

a) phosphate head group (hydrophilic)
b) FA tails (hydrophobic)
c) divides ICF and ECF (intra + extra)

Question 5

Info about cholesterol

Answer 5

a) scattered throughout membrane
b) adds stability to the cell membrane

Question 6

Info about membrane proteins (2 types)

Answer 6

a) Integral proteins
- integrated w/in membrane, so have a hydrophobic region
- some extend across entire membrane and =
transmembrane proteins
b) Peripheral proteins
- ! attached to either surface of integral proteins (i.e. on
the periphery of the cell membrane)
Functions of both types: enzymes, transporters, channels, receptors, anchors, and identity markers (for immune system)

Question 7

Info about membrane carbohydrates

Answer 7

• ! only on outer surface
• bound to proteins (glycoproteins) or lipids (glycolipids)
• functions:
  a) cell recognition e.g. sperm recognize egg cell
  b) anchor cells together

Question 8

Info about microvilli

Answer 8

• small projections of cell membrane
• function = to increase surface area
• best seen on cells of the small intestine and kidney

Question 9

What is (2) cytoplasm?

Answer 9

• The area btw. the inside of the cell membrane and outside
  of the nucleus
• 2 divisions:
  
  1. Cytosol = gel-like intracellular fluid
     
     • contains water, ions (like K+, Na+) and suspension of
       carbs, proteins, and lipids
     • may contain inclusions like melanin (pigment), glycogen
       (stored glucose)
  2. Organelles (small organs)
     
     • structures that perform a specific function and are
       essential for life
     • are either:
       a) non-membranous - in direct contact w/ cytosol
       b) membranous - surrounded by membrane that
       isolates them from cytosol

Question 10

What are the 3 types of non-membranous organelles?

Answer 10

1. Ribosomes
2. Centrosomes
3. Cytoskeleton

Question 11

Info about ribosomes

Answer 11

• sites for protein synthesis
• contain ribosomal RNA (rRNA) and proteins
• may be:
  a) free ribosomes - float in cytosol and make proteins that
  go to cytosol, mitochondria, and/or nucleus
  b) attached to endoplasmic reticulum (ER) - make proteins
  destined for other sites

Question 12

Info about centrosomes

Answer 12

• consist of 2 components: pair of centrioles and the
  pericentriolar matrix
• organizing centers for microtubules
  a) spindle apparatus (for cell division)
  b) organizes cytoskeleton

Question 13

Info about cytoskeleton (skeleton of the cell)

Answer 13

• ALL types are for structural support (for cell shape) and are
  formed from proteins
• Imp. in cell mvmt., cell division, mvmt./anchoring of
  organelles and proteins (like receptors, enzymes)
• 3 types:
  a) microfilaments (made of protein called actin)
  - functions = muscle contraction (w/ myosin), cell
  locomotion, and cytokinesis (cell mvmt.)
  b) intermediate filaments (composition is tissue specific -
  ex. = keratin)
  c) microtubules
  - hollow tubes made of protein tubulin
  - functions:
  - form (centrioles, spindle apparatus, cilia [short],
  flagella [long and only on sperm])
  - structural
  - move or secure organelles in place

Question 14

What are the 4 types of membranous organelles?

Answer 14

1. Mitochondria
2. Endoplasmic reticulum (ER)
3. Golgi Apparatus/Complex
4. Lysosomes

Question 15

Info about mitochondria

Answer 15

• site of ATP synthesis
• contains own DNA, RNA, and proteins
• have a double membrane

Question 16

Info about endoplasmic reticulum (ER)

Answer 16

• membranous network throughout cytoplasm
• 2 types:
  a) Rough ER (RER)
  - ribosomes attached - synthesis of secretory, lysosomal
  and membrane proteins
  b) Smooth ER (SER)
  - lacks attached ribosomes
  - continuous w/ RER
  - synthesizes lipids and steroid hormones

Question 17

Info about golgi apparatus/complex

Answer 17

• stacks of membrane discs
• mod.s proteins (ex.s = trims or adds carbs and lipids), sorts,
  packages, and delivers them to cell membrane, lysosomes,
  or for secretion (cellular post office)

Question 18

Info about lysosomes

Answer 18

• filled w/ digestive enzymes
• digest bacteria, viruses, worn-out organelles (clean up
  function)

Question 19

What is (3) the nucleus?

Answer 19

• the largest membranous organelle
• cell control center
• cells may have 1 or more nuclei
• parts:
  
  1. nuclear envelope
     
     • double membrane w/ nuclear pores
     • connected to ER
  2. nucleolus (> 1 in some plants)
     
     • non-membranous
     • dense (less light gets thru) region of DNA, RNA, proteins
       where ribosomes are made and assemble
  3. chromosomes/chromatids
     
     • contain DNA and histone proteins
     • can be:
       a) dispersed = Chromatin
       - DNA uncoiled and not individually visible
       - in this form MOST of the time (when cell is not
       dividing)
       b) condensed and individually visible
       - found in dividing cells (during mitosis/meiosis)