ch.10 eukaryotic cell biology

Question 1

Know how many proteins an mRNA code for in prokaryotes and in eukaryotes.

Answer 1

prokaryotes: several seperate proteins
Immature eukaryotes: several protein
Mature eukaryotes: single protein

Question 2

Contrast where in the cell transcription and translation occur in prokaryotes and in eukaryotes.

Answer 2

Eukaryotes:
transcription; nucleus, wehre DNA is
translation: ribosome
Prokaryotes:
transcription: cytoplasm (right next to each other)
translation: cytoplasm (next to each other)

Question 3

Explain what exons and introns are and describe the fate of each.

Answer 3

intron: process of removing entire sections of mRNA and throwing them away
exons: the remaining segments that are spliced together again after introns come toproduce the mature mRNA transcript
fate of both are to be passed out of the nucleus through nuclear pores to dock onto a ribosome and be translated into protein

Question 4

Describe what a lysosome is, how it functions, and explain why it doesn’t consume itself.

Answer 4

lysosome: vesicles full of digestive enzymes; break down structures of food into it’s essential building blocks and old, dysfunctional organelles to be recycled after fusing with them
Functions: fuses with H+ pump, H+ are pumped into lysosome, concentration of H+ in lysosome increases, which increases its acidity, lowering pH, and digestive enzymes are activated

Question 5

What protein are microtubules made of? Name a function of microtubules?

Answer 5

tubulin; used when compression is main force to be resisted

Question 6

What protein are microfilaments made of? Name a function of microfilaments?

Answer 6

actin; contribute to essential cellular activities like endocytosis and locomotion

Question 7

Name the protein intermediate filaments are made of, and list one function of intermediate filaments.

Answer 7

vimentin; anchors nucleus and other organelles, holds all cell parts together in right location

Question 8

Describe three different ways that Eubacteria and Eukaryotes differ in their mechanisms of protein synthesis (includes both transcription and translation). Note, this overlaps quite a bit with questions 1-3 above.

Answer 8

1. Eubacteria transcription and translation occur in the same place and time. Eukaryotes transcription occurs in nucleus and translation occurs outside the nucleus.
2. Eubacteria: several genes are coded at a time. Eukaryotes: one gene is coded by mRNA.
3. Eubacteria has no mRNA processing. Eukaryotes have 5’ cap, 3’ A tail, and splicing.

Question 9

Describe RNA processing in Eukaryotes. Use the following words: nucleus, exon, intron, primary RNA transcript, mature RNA transcript, 5’ cap (function), 3’ poly-A tail (function).

Answer 9

First, you start off with a piece of DNA that is going through the process of transcription. The mRNA gets longer and there are exons and introns on
5’–>3’ mRNA transcript. Then , a 5’ cap and poly A tail are added to protect the mRNA and form the signal on the mRNA that allows it to say that it needs to exit the nucleus. After, introns are thrown away and meets up with the ribosome to be translated.

Question 10

Alternative splicing: Be able to both draw and explain in words how two different proteins
can be made from a single mRNA containing several introns and exons.

Answer 10

First, there’s the primary transcript mRNA. Then, exon 4 is thrown away with the introns as well as exons 5&6. After both exons 1-4 and 1-3+5-6 are placed together and spliced to get the mature mRNA that gets translated into the two proteins.

Question 11

Describe with words and/or drawings the steps by which eukaryotes package their gene products, both for proteins that will remain in the cytoplasm, and those destined for other locations. Use the words, cytoplasm, ribosome, rough endoplasmic reticulum, smooth endoplasmic reticulum, transport vesicle, golgi apparatus, cis face, trans face.

Answer 11

After the newly produced protein docks onto the ribosome, it’s moved into the endoplasmic reticulum. It then enters the golgi apparatus through the cis face and exits from the trans face. When it leaves, they have a tag so that it can be sorted and transported. In the rough endoplasmic reticulum, proteins are folded and tagged.

Question 12

Be able to describe the three main fates of protein products after they leave the Golgi apparatus (cytoplasmic proteins, exported proteins, lysosomal proteins). Use the words lysosome, exocytosis, phagocytosis, vesicle fusion, proton pump, acidic environment, digestive enzymes.

Answer 12

1. Golgi apparatus can repackage the protein into secretory vesicles that are bound for phagocytosis in reverse. This removes large amounts of material from inside the cell.
2. Golgi apparatus can be repackaged into lysosomes which must fuse before activating the proton pump. More proteins allows the lysosome to become more acidic to activate the digestive enzymes.
3. Cytoplasmic proteins don’t go through the Golgi apparatus and is synthesized in the cytoplasm by free ribosomes.