The nucleus and the Cell membrane of eukaryotes

Question 1

what’s the major feature that distinguishes a eukaryotic cell from prokaryotic cell?

Answer 1

nucleus of the eukaryotic

Question 2

what is the nucleus for?

Answer 2

it contains all of the DNA in an animal cell (except for the small amount that’s in the mitochondria)

Question 3

the double phospholipid bilayer that is wrapped around the nucleus is what?

Answer 3

the nucleus envelope of the membrane

Question 4

what are nuclear pores?

Answer 4

the nucleus envelope is perforated with large holes
- the RNA can exit the nucleus though the nucleus pores
but the DNA cannot

Question 5

what is the nucleolus?

Answer 5

its within the nucleus , its where rRNA is transcribed and the subunits of the ribosomes are assesmbled.
its not separated from the nucleus by a membrane

Question 6

Endocytosis is what?

Answer 6

when the cells can get substances from the extracellular environment through endocytosis

Question 7

what are the different types of endocytosis?

Answer 7

phagocytosis: to eat
pinocytosis : to drink
receptor mediated endocytosis

Question 8

what happens in phagocytosis?

Answer 8

cell membrane will protrude outwards to envelope and engulf particulate matter. only a few speaciliazed cells are capable of phagocytosis.
once the particulate matter is engulfed, the membrane body is called a phagosome.

Question 9

what happens in pinocytosis?

Answer 9

extracellular fluid is engulfed by small invaginations of the cell membrane. its non selective and performed by most cells.

Question 10

what happens in receptor mediated endocytosis?

Answer 10

specific uptake of macromolecules like hormones and nutrients.

Question 11

how is receptor mediated endocytosis different than phagocytosis?

Answer 11

receptor mediated endocytosis: purpose is to absorb ligands.

phagocytosis: ligands exist only to act as signals to initiate phagocytosis of other particles

Question 12

what is exocytosis?

Answer 12

reverse of endocytosis

Question 13

Granular or rough ER

Answer 13

ER near the nucleus , has many ribosomes attatched to it on the cytosolic side , giving it a granular appearance
proteins made on the rough ER are pushed into the ER lumen and sent to the golgi.

Question 14

what is the golgi?

Answer 14

series of flattened, membrane bound sacs

the golgi can change proteins chemically by glycosylation or by removing amino acids.

Question 15

how are proteins distinguished?

Answer 15

based upon their signal sequence and carb chains.

Question 16

what are the end products of golgi?

Answer 16

vesicle full of proteins. these protein filled vesicles may either be expelled from the cell as secretory vesicles , released from the golgi to mature into lysosomes, or transported to other parts of the cell such as mitochondria or even back to the ER

Question 17

What is important about secretory vesicles?

Answer 17

they contain enzymes, growth factors or extracellular matrix components.

• they release their contents through exocytosis.
• since exocytosis incorporates vesicle membranes into the cell membrane, secretory vesicles also act as the vesicle with which to supply the cell membrane with its integral proteins and lipids, and as the mechanism for membrane expansion.
• in reverse process, endocytotic vesicles made @ cell membrane are shuttled back to golgi for recycling of the cell membrane.
• some proteins are activated in the secretory vesicles.

Question 18

what is a lysosome?

Answer 18

contains acid hydrolyses such as proteases, lipase, nucleases, glycosides. together these enzymes can break down every major type of macromolecule within the cell.

• lysosomes generally have an interior pH of 5
• these fuse with endocytotic vesicles ( formed by phagocytosis and pinocytosis) and digest their contents- when lysosome ruptures their content is released in the cell and the cell dies : this is called autolysis

Question 19

what is the agranular or the smooth endoplasmic reticulum?

Answer 19

it has glucose-6-phosphate , enz used in the liver and other places to hydrolyze glucose 6-phosphate to glucose. ( an important step in the production of glucose from glycogen)
- triglycerides are made in the smooth ER and stored as fat
the smooth ER and cytosol share a role of cholesterol formation and its subsequent conversion to various steroids.
- most of the phospholipids are made in the SER

Question 20

What are some other functions of the SER?

Answer 20

Oxidize foreign substances, detoxify drugs, pesticides, toxins and pollutants.

Question 21

what are peroxisomes?

Answer 21

are vesicles in the cytosol. they grow by incorporating lipids and proteins from the cytosol.
rather then budding off membranes like lysosomes from the golgi, peroxisomes self replicate.

Question 22

what do the peroxisomes do?

Answer 22

involved in the production and breakdown of hydrogen peroxide. they inactivate toxic substances like alcohol, regulate oxygen concentration etc