The Cell

Question 1

8 General Cellular Functions

Answer 1

1. Covering
2. Lining
3. Storage
4. Movement
5. Connection
6. Defense
7. Communication
8. Reproduction

Question 2

3 Characteristics most cells have

Answer 2

• Plasma (cell) membrane
• Cytoplasm
• Nucleus

Question 3

Plasma (Cell) Membrane

• function
• major constituents

Answer 3

• Phospholipid bilayer that is the extremely thin outer border on cell that selectively mediates what enters & leaves cell (gases, nutrients & wastes)
• Made of 2 components;
  1. Lipids
  
  • Phospholipids (75%): hydrophilic polar head & hydrophobic nonpolar tail - constitutes majority of lipid in cell membrane
  • Cholestrol (20%): strengthens & stabilises membrane against extreme temp.
  • Glycolipids (5-10%): Have carbohydrate molecules attached & facing out - forms the glycocaylx (involved in cell - cell recognition.
    
    2. Proteins: Are complex molecules made of amino acid chains that give membrane functions
       i) Integral: partially or fully embedded in membrane (e.g. channels)
       ii) Peripheral: Proteins attached to surface - help w/ cell signalling
• Both can serve as enzymes

Question 4

Cytoplasm - 3 parts

Answer 4

*Includes all materials between plasma membrane & nucleus
3 parts;
-Cytosol; Viscous, syrup-like fluid containing many different dissolved substances (e.g. ions, nutrients, proteins, aa, carbs)
-Inclusions: Large storage aggregates of complex molecules found in cytosol (e.g. melanin - pigment, glycogen - long chains of sugars in liver & skeletal muscles)
-Organelles: Membrane bound or non-membrane bound structures that have unique functions and activities

Question 5

Smooth Endoplasmic Reticulum (SER)

• General features of ER
• Function of SER

Answer 5

*network of intracellular membrane w/ enclosed spaces called cisternae.
-walls have smooth appearance -lack of ribosomes.
Functions;
-Synthesis, transport & storage of lipids (e.g. hormones & steroids)
-Metabolism of carbohydrates
-Detoxification of drugs, alcohol & poisons

Question 6

Rough Endoplasmic Reticulum (RER)

-Function

Answer 6

-Rough wall appearance due to ribosomes (protein synthesizers)
-continuous w/ SER
Synthesise, transport or store proteins for;
-secretion by cell
-Incorporation into plasma membrane
-creation of lysosomes

Question 7

Golgi Apparatus

• Function
• Terminology for 2 regions

Answer 7

-stacked cisternae - lateral edges bulge, pinch off & give rise to small transport & secretory vesicles
-receives proteins & lipids from RER for modification, sorting & packaging
Receiving region = cis-face
Shipping region = Trans-face

Question 8

Lysosomes

• Function
• Autophagy & autolysis

Answer 8

• Are vesicles generated by Golgi Apparatus (or membrane sacs filled w/ digestive fluid)
• Contain enzymes that are used to digest & remove waste products/damaged organelles w/n cell (Autophagy)
• Lysosomes release their enzymes that digest cell when dying (Autolysis)

Question 9

Peroxisomes

Answer 9

• Vesicles smaller than lysosomes.
• Are membrane enclosed sacs that usu. contain large amounts of specific enzyme to break down harmful substances
• Use O2 & enzymes to catalase (detoxify) harmful molecules taken into cell
  
  • hydroxide to H2O
  • Are able to break down fatty acids

Question 10

Mitochondria

• shape
• where ATP produced

Answer 10

• Bean shaped organelles w/ double membrane (inner forms cristae; has internal fluid matrix)
• Produce ATP (high energy containing molecule) ON THE cristae
• Referred to as the “powerhouses of the cell”

Question 11

Ribosomes

-Free & fixed ribosomes

Answer 11

• Made up of small & large subunit - are dense cytoplasmic granules
• Responsible for protein synthesis
• Free Ribosomes: float unattached w/in cytosol - synthesize proteins for use in cells
• Fixed Ribosomes: attached to outer surface of RER; synthesis proteins for secretion, incorporation into plasma membrane or lysosomes

Question 12

Cytoskeleton

-3 parts

Answer 12

-Is an organised network of protein filaments or hollow tubules throughout cell
-Provides structural support; facilitates cytoplasmic straming, organelle & cellular motility, transport of materials & chromosomal movement & cell division.
3 Parts;
1. Microfilaments: Actin protein monomers formed into filaments (used to maintain cell shape, aid in muscle contract. & separate dividing cells)
2. Intermediate filaments: Various protein components - provides structural support, stabilises cell junctions
3. Microtubules: Hollow cylinders of tubulin proteins; able to lengthen & shorten - support cell, hold organelles in place, maintain cell shape & rigidity, direct organelle movement w/in cell as cilia & flagella; move chromosomes @ cell division

Question 13

Centrosome & Centrioles

Answer 13

Centrosome: Amorphous regionattached to nucleus; contains a pair of centrioles at right angles to each other
Centriole: Nine sets of microtubule triplets
-involved in organising microtubules
-attach to chromosomes during cell division - causes chromosomal migration

Question 14

Cilia & Flagella

Answer 14

• Projections on the cell containing cytoplasm & microtubules capable of movement
• Cilia: On cells that move objects across their surface (i.e. cells of respiratory tree & oviduct)
• Flagella: longer, usu. singular, to propel a cell (e.g. sperm)

Question 15

Microvilli

Answer 15

• Extensions of cell NOT capable of motion (altho. look like cilia are in fact much smaller)
• Purpose is to increase SA to increase absorption of food (found on surface of cells of small intestine)

Question 16

Nucleus

-Chromatin vs. Chromosomes

Answer 16

-Control centre for cellular activity - controls protein synthesis which directs functional & structural characteristics of cell
-Contains DNA
Chromatin: unwound form DNA takes when not dividing
Chromosome: wound up form DNA takes when dividing

Question 17

Nuclear Envelope, Nuclear Pores & Nucleolus

Answer 17

Nuclear Envelope: Double membrane structure that is the physical barrier between the nucleus to cytoplasm
-outer membrane continuous w/ ER
Nuclear Pores: Openings in nuclear envelope - is what allows passage of materials
Nucleoulus: spherical, dark staining, dense granula region w/in nucleus - responsible for making small & large subunits of ribosomes

Question 18

Life Cycle of Cell

Answer 18

• Cell always in one of two stages:
  1. Interphase: Maintenance phase between divisions where cell either prepares for division or undergoes normal activities. Is where cell spends majority of its time.
  2. Mitotic Phase: When cell divides (Chromatin to chromosomes)