A2.1 and A2.2 - Origin of Cells and Cell Specialization

Question 1

Modern Cell Theory

Answer 1

• All living things are composed of cells and cell products
• New cells are formed only by the division of pre-existing cells
• Cell contains inherited information (genes) used as instructions for growth, functioning, and developments (spontaneous generation doesn’t occur)
• The cell is the functioning unit of life, all of the chemical reactions (need energy) of life take place within cells

Question 2

Magnification

Answer 2

M=I/A=observed size/actual size
1mm=1000um
1um=1000nm

Question 3

Resolution

Answer 3

• ability to distinguish between two separate points, if two points cannot be resolved they will be seen as one
  limit of resolution = wavelength/s

Question 4

Compound Microscope

Answer 4

• aka brightfield microscope
• around 1000x
• 0.2um resolution
• two or more separate lenses
• thin and mostly transparent sample so light can pass through, stained specimen

Question 5

Dissecting Microscope

Answer 5

• aka stereomicroscope
• binocular microscope
• around 4x to 50x
• 120nm resolution
• two separate lens systems
• 3D view of speicmen
• used for dissection of specimen or sample

Question 6

Phase Contrast Microscope

Answer 6

• 1000x , 0.2um resolution
• used for examing live biological specimen
• enhances contrasts of transparent and colorless objects (differential phase contrast)
• pseudo 3D effect
• In phase (constructive interference, brighter light)
• Out of phase (destructive interference, dimmer light)

Question 7

Confocal Microscope

Answer 7

• 0.1um res, 1000x)
• fluorescent dye
• uses laser light focused on a small region of the specimen
• laser scans whole surface of specimen and images each spot captured
• software combines all images into one sharp image
• used to capture image of specimen + used for generation of 3D images

Question 8

Fluorescent Microscopy

Answer 8

• 0.2um res, 1000x)
• used to study specimens that can be made to fluoresce
• mercury arc lamp

Question 9

Transmission Electron Microscope

Answer 9

• 0.5nm res, magnifies 50 million times
• used to examine ultrastructure of extremely thin sections of materal (made using ultramicrotome)
• electrons pass through specimen and are scattered, only electrons that are transmitted are viewed
• magnetic lense focus image on a fluorescent screen or photographic plate
• kept in vacuum to prevent scattering of electrons + sample dehydrated

Question 10

Scanning Electron Microscope

Answer 10

• less than 50pm res, upto 30 million times magnified
• produces detailed 3D surface image of small organisms
• electrons bounce off of specimen
• specimen coated in gold so that electrons deflect
• viewed on viewing screen or photographic plate

Question 11

Atomic Force Microscopy

Answer 11

• used to find geography of sample
• used surface tension to find contour details
• used for 3D surface profile

Question 12

Freeze Fracture

Answer 12

• instantly frozen solid in liquid nitrogen
• solid tissue broken in vacuum, exposed surfaces lose some ice (etched surface)

Question 13

Cell wall

Answer 13

• outside plasma membrane
• between the walls of adjacent cells is sticky substance called middle lamella
• made of cellulose
• protects cell, maintains cell shape, prevents excessive water uptake

Question 14

Nucleus

Answer 14

• contains chromatin (cell’s genetic material) within nuclear membrane
• responsible for regulating cell activity

Question 15

Nucleolus

Answer 15

• synthesis of ribosomal RNA
• assembly of RNA subunits
• mass of dark stained granules and fibers

Question 16

Golgi Apparatus

Answer 16

• series of flattened continuous sacs
• sorting, packing, and storage of proteins and lipids
• modified proteins and lipids received from the ER
• transports materials using vesicles
• manufacture of certain macromolecules
• aids formation of cell wall by synthesizing cellulose
• lysosome + acrosome formation

Question 17

ER

Answer 17

Rough ER:
- complex system of mebranous tubules covered in ribosomes
- synthesis, folding, and modification of proteins
- transport of protein throughout cell
- membrane synthesis
Smooth ER:
- no ribosomes
- synthesis of lipids
- membrane synthesis
- carbohydrate metabolism
- transport of these materials through cell
- detoxification of drugs and poisons

Question 18

Ribosomes

Answer 18

• protein synthesis
• act as catalase for some reactions
• Prokaryote: 70S (50+30)
• Eukaryote: 80S (60+40)

Question 19

Lysosome

Answer 19

• lipid membrane-bound sac
• breaks down foreign material
• uses amylase, nuclease, phosphoric acid etc by extracellular and intracellular digestion
• 4-6.5 pH

Question 20

Microtubules

Answer 20

• long, cylindrical, hollow organelles
• made of tubulin proteins: alpha and beta
• many dimers polymerize to form filaments
• constantly change according to cell’s needs
• maintain cell shape and structure
• intracellular transport of secretory vesicles, lysosomes, and mRNA

Question 21

Centrosome

Answer 21

• area in cell where microtubules are produced

Question 22

Centriole

Answer 22

• replicate during cell division, resulting in two chromosomes
• usually close to nucleus
• involved in organizing microtubule assembly

Question 23

Pili

Answer 23

• hair-like structures that are rigid (not associated with movement)
• adhere/attach to surfaces
• sex pilus: transfer of genetic material (plasmid) from one bacteria to another

Question 24

Plasmid

Answer 24

• carry genes for replicating DNA, transferring them from one host cell to another
• for variety of phenotypes
• carry genes give antiobiotic resistance to the host cell

Question 25

Flagella

Answer 25

- threads of protein - motility - number and arrangement vary - in bacterial