Cell Biology

Question 1

What was the importance of the electron microscope in cytology?

Answer 1

-Electrons have a much shorter wavelength than light. -Therefore produces images with a better resolution.

Question 2

What is the resolution (resolving power) of a microscope?

Answer 2

-Ability to discern detail. -Can be expressed as the smallest distance between 2 objects that can be distinguished as separate.

Question 3

What is the magnification (linear mag) of a microscope?

Answer 3

-size of an image compared to the size of the object.

Question 4

what is the equation of magnification?

Answer 4

MAG = length of image/length of object

Question 5

What can a light microscope do?

Answer 5

-can magnify to an unlimited extent -image becomes bigger and more blurred, without showing extra detail (poor resolution).

Question 6

What does an electron microscope use?

Answer 6

• beam of electrons instead of light. - e(-) have shorter wavelength (0.004nm) -Can achieve useful magnifications of up to x500,000

Question 7

What are the limitations of electron microscope?

Answer 7

• prep procedures - strength of the lenses.

Question 8

What is TEM, and how does it work?

Answer 8

-Transmission electron microscope -work by sending a beam of e(-) through a very thin slice of material, creating a 2D image -to produce constrast, the material is stained by heavy metals that will scatter the e(-).

Question 9

What is SEM, and how does it work?

Answer 9

-Scanning e(-) microscopes -creates 3D images by bouncing e(-) off the surface of a material that has been coated with a heavy metal. -magnification is less compared to TEM (x20,000)

Question 10

1 micrometer …

Answer 10

= 0.001mm =10 to the power of -3 mm (1 mm = 1000 micrometers)

Question 11

1 nanometer…

Answer 11

= 0.001 micrometer = 10 to the power of -3 micrometers (1 micrometer = 1000 nanometer)

Question 12

what is the average animal cell diameter?

Answer 12

15 micrometer

Question 13

what is the average red blood cell diameter?

Answer 13

7 micrometers 7000 nanometers 7 to the power of -6 metres

Question 14

what is the cell ultrastructure?

Answer 14

refers to the structure as seen with the e(-) microscope.

Question 15

where are organelles visible?

Answer 15

in the cytoplasm of the cell

Question 16

what is structure and function of nucleus

Answer 16

-contains the chromosomes, is surrounded by a nucleus envelope with pores. -Also contains the nucleolus. -The DNA on the chromosomes controls the cell by controlling protein synthesis.

Question 17

what is structure and function of nucleolus

Answer 17

-Darker stained (denser) area within the nucleus. - site of synthesis of rRNA

Question 18

what is structure and function of cell membrane

Answer 18

• A phospholipid bilayer, which associated proteins etc. - It surrounds the whole cell. -controls movement of substances in and out of the cell.

Question 19

what is structure and function of ribosomes

Answer 19

• small particles containing proteins and RNA. -protein synthesis

Question 20

what is structure and function of rough endoplasmic rectiumulm (RER)

Answer 20

• membrane systems with associated ribosomes. -they run through the cytoplasm and form flatterned sacs. -synthesis (on the ribsosmes) and transport of proteins within the cell.

Question 21

what is structure and function of smooth endoplasmic recticulum (SER)

Answer 21

• Membrane systems without ribosomes, forming sacs and tubules. - synthesis and transport of lipids and steroids.

Question 22

what is structure and function of Glogi appartus?

Answer 22

-dense systems of membranes and sacs, with associated vesicles. -site of modification of proteins (e.g. synthesis of glycoproteins) and packaging them into vesicles (e.g. secretion from the cell) or formation of lysosomes.

Question 23

what is structure and function of Lysosomes

Answer 23

-membrane bound compartments, containing hydrolytic enzymes. - digestion and destruction of worn out organelles or particles taken into cell by phagocytosis.

Question 24

what is structure and function of mitochondria

Answer 24

-rod shaped structures, surrounded by a double membrane: inner membrane is founded into cristae. -site of aerobic respiration: Krebs’ cycle (in the matrix) and oxidative phosphorylation (on cristae).

Question 25

what is structure and function of centrioles

Answer 25

-cylindrical structures formed from nine groups of protein microtubules. NOT PRESENT IN PLANT CELLS. -concerned in the organisation of the spindle during cell division.

Question 26

what is structure and function of cytoplasmic matrix

Answer 26

• the background material of the cell cytoplasm. - mostly water, containing proteins, ions (Na+, K+, Cl-) and other solutes. - many chem reactions occur here. (e.g. the glycolytic pathways of anaerobic respiration).

Question 27

what are eukaryotic cells

Answer 27

-animal and plant cells are relatively large with complex internal structures and a TRUE MEMBRANE BOUND NUCLEUS.

Question 28

what are prokaryotic cells

Answer 28

bacterial cells, they are simpler.

Question 29

what are the main differences in prokaryotic cells

Answer 29

-no true nucleus or nuclear envelope. The genetic material is free in the cytoplasm= nucleoid. -fewer organelles, no membranous organelles such as endoplasmic reticulum or Golgi. -ribosomes are present, but they are smaller. -genetic material is in the form of a single circular strand of DNA (NOT A TRUE CHROMOSOME), plus smaller rings of DNA in the cytoplasm= PLASMIDS. -Cell wall, but not made of cellulose- made of peptidoglcans. Sometimes the cell wall is surrounded by a protective capsule. -the whole cell is SMALLER (around 1 micrometer) -some bacteria have pili (for attachments) and a flagellum (for movement), but these are not always present.

Question 30

what is cell fractionation and the benefits

Answer 30

-cells are broken up and the different types of organelles are separated from each other. -we can get a suspension containing a single type of organelle, which can be further investigated by e.g. chemical analysis.

Question 31

what is homogenisation

Answer 31

-the process of breaking up cellular material e.g. in a blender. -this is done in a with the material immersed in 1. An ice cold (so enzymes stop working), 2. Isotonic (so organelles don’t swell or shrink due to osmotic effects), 3. Buffer (to maintain pH at the correct level) solution.

Question 32

what is differential centrifugation

Answer 32

• the homogenate (mixture) is filtered and spun at progressively higher and higher speeds. -the larger/denser organelles sediment first (forming a pellet at the bottom). -the supernatant (liquid part) is then poured off, and centrifuged at a higher speed. -the next largest organelles then sediment out as a new pellet. -this can be repeated at higher and higher speeds, to give different fractions containing different cell components. -the different fractions can then be subjected to analysis: e.g. identifying chem composition, or looking for tracer chemicals.

Question 33

what is the order of cell components separated during the differential centrifugation process

Answer 33

1. nuclei= 500rpm, force of 600g 2. mitochondria, lysosomes= force of 15,000g 3. fragments of ER and cell membrane= 50,000 rpm 4. ribosomes= force of 300,000g 5. cytoplasmic matrix and its soluble components.

Question 34

what are the units svedberg (S)

Answer 34

that rate at which the particles sediment out in centrifiguation

Question 35

what is chromatography and the process

Answer 35

-separates out the chemicals in a mixture so they can be identified. -A mixture is placed onto a background material (e.g. onto paper or gel). -A solvent moves through this background material, drawing the components of the mixture with it, -the components of the mixture are separated according to their solubility in the solvent and their affinity for a background. Different substances move different distances.