Nuclesus And Ribosomes

Question 1

What is an evolutionary advantage of the nucleus?

Answer 1

Membrane infolding to increase surface area of surrounded DNA

Question 2

Outline 2 critical functions of the nucleus?

Answer 2

• contain & protect DNA
• Co-ordinates cellular activity

Question 3

What size is the nucleus?

Answer 3

5um

(2-10 um)

Question 4

Describe the 2 concentric membranes of nuclear envelope;

Answer 4

•inner
Binding of chromosomes
Anchors for nuclear laminate

•outer
Continous with ER

Question 5

What is the job of the nuclear envelope?

Answer 5

Import and export of molecules accomplished via nuclear pore complex’s

Question 6

What does each nuclear pore contain?

Answer 6

Eightfold symmetric ring-shaped structure

Question 7

What is attached to the nuclear pore?

Answer 7

Nuclear basket which extends into the nucleoplasm

Series of filamentous extensions that reach into the cytoplasm

Question 8

Describe passive transport in nucleoplasmic transport

Answer 8

Bidirectional

Free movement of;
- water
-ions
-metabolites
-proteins

Question 9

Describe active transport in nucleoplasmic transport

Answer 9

Signal sequences

-nuclear localisation signal (NLS) recognised by importin

-nuclear export signal (NES) recognised by exportin

Question 10

What is nuclear lamina?

Answer 10

Dense fibrillar network inside the nucleus of eukaryote cells

Question 11

What is nuclear lamina composed of?

Answer 11

Intermediate filaments and membrane associated proteins

Question 12

What does nuclear lamina provide?

Answer 12

Mechanical support, regulated important cellular events such as DNA replication and cell division

Question 13

What does nuclear lamina participate?

Answer 13

Participates in chromatin organisation and anchors the nuclear pore complexes embedded in the nuclear envelope

Question 14

What is the nucleolus?

Answer 14

Largest structure in the nucleus’s of eukaryotic cells

Site of ribosome biogenesis

Question 15

Describe 3 major components of the nucleolus;

Answer 15

(1) fibrillar centre (FC)

(2) dense fibrillar component (DFC)

(3) granular component (GC)

Question 16

What occurs in the fibrillar centre (FC)?

Answer 16

Transcription of the rDNA

Question 17

What does the dense fibrillar component contain?

Answer 17

Contains the protein fibrillarin which is important in the rRNA processing

Question 18

Describe ribosomes;

Answer 18

Decode mRNA message into protein (translation)

Typical cell has millions of ribosomes

Question 19

Describe ribosomal RNA?

Answer 19

Type of non coding RNA which is the primary component of ribosomes

Question 20

What is rRNA carry out?

Answer 20

Protein synthesis in ribosomes

Question 21

Describe the small unit of ribosomes;

Answer 21

30+ proteins

1x rRNA

Question 22

Describe the large unit of ribosomes;

Answer 22

40+ proteins

3x rRNAs

Question 23

What is the function of the small unit ribosome?

Answer 23

Matches the tRNAs to the mRNA codons

Question 24

What is the function of the large unit ribosome?

Answer 24

Catalysed the formation of peptide bonds

Question 25

Describe the s of prokaryotic and eukaryotic ribosomes

Answer 25

• Prokaryotic
50S + 30S = 70S

• eukaryotic
60S + 40S = 80S

Question 26

What does s stand for in ribosomes?

Answer 26

Svedberg units of sedimentation

Question 27

What is the function of a translational machinery ribosomes?

Answer 27

Catalyse the joining of the amino acid monomers directed by the mRNA sequence

Question 28

Each ribosome has;

Answer 28

Binding site for mRNA

three binding sites for tRNA
(A,P&E)

Question 29

Describe A&P sites;

Answer 29

A= aminoacyl & P=peptidyl sites

A irked on ribosome where charged tRNA molecules bind during peptide synthesis

Question 30

Describe E sites;

Answer 30

E= exit site

Discharged tRNAs leave the ribosome