Cell Structure and Genetic Control, Ch 3

Question 1

Which 2 cell types are able to create “pseudopods” to eat/expel bacteria or other microorganisms?

Answer 1

White blood cells - neutrophils

macrophages - connective tissue cells

Question 2

What is pinocytosis?

Answer 2

A form of endocytosis that is nonspecific. The plasma membrane invaginates to produce a deep furrow, the membrane near the surface fuses, and a small vesicle containng the extracellular fluid is pinched off and enters the cell.

Question 3

What is Exoxytosis?

Answer 3

• Process by which cellular products are secreted into the extracellular environment. Proteins/carbs/everythign is packaged in the Golgi and then sent to fuse and be relased by plasma membrane.

Question 4

In areas of the body that are specialized for rapid diffusion, the surface area of the cell membranes may be increased by numerous folds called…..

Answer 4

microvilli

Question 5

The cytoskeleton of a cell is formed by a latticework of what 2 things?

Answer 5

microfilaments and microtubules

Question 6

What are 3 functions of microtubules?

Answer 6

1. Form a track along which motor proteins move their cargo through the cytoplasm
2. form the spindle apparatus that pulls chromosomes away from each other during cell division
3. Form central parts of cilia and flagella and contribute to structure and movements of these projections from the cell

Question 7

Is a primary lysosome more acidic than its cytoplasmic environment? How do you create a secondary lysosome?

Answer 7

1. Yes
2. Fuse a primary lysosome with a food vacuole - it now contains engulfed extracellular material

Question 8

What is autophagy?

Answer 8

The digestion of structures and molecules within a vacuole by the enzymes within a lysosome.

Question 9

What are functions of Peroxisomes?

Answer 9

1. remove hydrogen from particular organic molecules - oxidize (enzymes are oxidase)
   
   1. Hydrogen is transferred to molecule oxygen forming hydrogen peroxide (H₂O₂)
2. Important in the metabolism of amino acids and lipids and production of bile acids
3. oxidize toxic molecules like formaldehydr and alcohol

Question 10

Which thyroid hormone stimulates the genesis of mitochondira?

Answer 10

Thyroxin

Question 11

Which part of the nucleosome is positively/negatively charged?

Answer 11

• The DNA helix is negatively charged
• The protein, histone, is positively charged

Question 12

Exons are spliced togehter by what ribosome-like aggregate of RNA?

Answer 12

snRNPS - small nuclear ribonucleoproteins

Question 13

What are siRNA, and what do the protect against?

Answer 13

• siRNA - short interfering RNA = formed from longer dsRNA that leave the nucleus and are processed in the cytoplasm by Dicer
• Helps combat viral infections - once it is process by Dicer it can then go mess with the viral DNA it came from?

Question 14

What is miRNA?

Answer 14

• miRNA - microRNA. Used in RNA interference
• Formed from longer RNA strands that fold into hairpin loops. Then they leave the nucleus and into the cytoplasm wheree Dicer cleaves the hairpin loop.
• Once side of the loop binds with a RISC (RNA-induced silencing Complex). THe whole complex of RISC and miRNA binds to a mRNA and silencing a gene expression.

Question 15

During protein synthesis, imporoper misfoldings are prevented by what?

Answer 15

Chaperones.

Question 16

Which molecule tags a protein for degradation? Where does this degradation take place?

Answer 16

1. Ubiquitin
2. Proteasome

Question 17

What is the “nondividing” life cycle of a cell called?

Answer 17

Interphase

Separated in G₁, S, G₂

Question 18

What are the characteristics of each Interphase phase, G1, S G2?

Answer 18

1. G1 - cells perform the phsiological functions characteristic of the tissue in which they are found. Basically cells are just acting normal. Centroles also replicate
2. S - DNA replication
3. G2 - final growth period happens, also the chromtin condenses.

Question 19

What does Cyclin D proteins do?

Answer 19

• An increase in Cyclin D activates a group of inactive enzymes called cyclin-dependent kinases, these move the cell quickly thorugh G1 and cause more rapid cell division
  
  • could cause uncontrollable cell division.

Question 20

Where do oncogenes come from (cancer genes)?

Answer 20

• Oncogenes are altered forms of normal proto-oncogenes, which code for proteins that control cell division and apoptosis.

Question 21

What is p53, and what does it do?

Answer 21

• important tumor suppressor gene
• it is a transcription factor. When there is damage to DNA, p53 acts to sall cell division, mainly at the G1 to S checkpoint.
  
  • could help fix DNA or just cause apoptosis so it is not replicated.

Question 22

What are the 4 stages of Mitosis?

Answer 22

Prophase

Metaphase

Anaphase

Telophase

Question 23

Major occurences of prophase?

Answer 23

1. Chromosomes are seen to consists of two chromatids joined by a centromere
2. centrioles move apart towards opposite poles of the cell
3. Spindle fibers are produced and extend from each centrosome
4. Nuclear membrane starts to disappear
5. Nucleolus is no longer visible

Question 24

What occurs during metaphase?

Answer 24

1. Chromosomes are lined up at the equator of the cell
2. Spindle fibers from each centriole are attached to the centromeres of the chromosomes
3. Nuclear membrane has disappeared

Question 25

What occurs during Anaphase?

Answer 25

1. Centromeres splits, and the sister chromatids separate as each is pulled to an opposite poll

Question 26

What occurs during Telophase?

Answer 26

1. Chromosomes become longer, thinner, and less distinct
2. new nuclear membranes form (cytokinesis)
3. nucleolus reappears
4. cell division is nearly complete

Question 27

Hyperplasia vs Hypertrophy

Answer 27

• Hyperplasia - growth that is due to an increase in cell number
• Hypertrophy - growth of a tissue or organ due to an increasein cell size