Organelles and Cytoskeleton

Question 1

What is chromatin?

Answer 1

Combined structure of proteins and DNA

Question 2

What is the role of nuclear pores?

Answer 2

Allows mRNA strands to exit the nucleus and proteins to enter the nucleus

Question 3

What type of RNA does the nucleolus produce?

Answer 3

Ribosomal RNA

Question 4

What are synthesised at the nucleolus?

Answer 4

Ribosomes

Question 5

What is the structure of the Golgi apparatus?

Answer 5

A single membrane consisting of cisternae

Question 6

What is added to lysosomal enzymes by the golgi, why?

Answer 6

Mannose-6-phosphate

Keeps them sequestered

Question 7

What is the role of the Golgi body?

Answer 7

Modifies proteins before packaging them into vesicles to leave the cell

Question 8

What are the two faces of the golgi apparatus, what do they do?

Answer 8

Cis-face where vesicles are received from the ER

Trans-face where vesicles are send out after modification.

Question 9

What is the structure of a mitochondria?

Answer 9

Oval shaped organelle, with a double membrane, the inner membrane is folded into cristae creating an internal matrix.

Question 10

What is the function of the mitochondria double membrane?

Answer 10

Energy from the electron transport chain can be used to pump H+ into the intermembrane space so its chemiosmosis can drive ATP synthase to produce ATP.

Question 11

What does the lysosome consist of?

Answer 11

Contains lyososymes which are digestive enzymes to degrade cellular waste

Question 12

What enzymes are lysosymes?

Answer 12

Acid hydrolases

Question 13

Why dont lysosymes digest cellular material?

Answer 13

Acidic nature - enzymes would be inactive in neutral pH.

Question 14

How is the acidic pH maintained in lysosomes?

Answer 14

Proton pump that pumps H+ into the lysosymes.

Question 15

Where are proteosomes present?

Answer 15

Nucleus and the cytoplasm

Question 16

What is the role of proteosomes?

Answer 16

Breaks down proteins through proteolysis

Question 17

How do proteosomes break down proteins?

Answer 17

Proteases are located in the central pore.

Question 18

What identifies a protein for breakdown?

Answer 18

Ubiquitin

Question 19

What metabolism are peroxisomes involved with?

Answer 19

Breakdown of very long chain fatty acids

Question 20

What roles do peroxisomes have other than VLCFA?

Answer 20

Breakdown of D(enantiomer)-amino acids

Reduction of reactive oxygen species, specifically hydrogen peroxide

Question 21

What are vesicles?

Answer 21

Small organelles containing a liquid or substance encased in a phospholipid bilayer

Question 22

What are the important roles of vesicles?

Answer 22

Transporting substances across the cell, via MT pathways and driven by motor proteins

Transporting substances into and out of cells by endo and exocytosis

Question 23

What is the structure of the RER?

Answer 23

Surrounds the nuclear membrane

Series of long fluid filled sacks that are dotted with ribosomes. It has many folds called cisternae

Question 24

What is the role of the RER?

Answer 24

Protein synthesis and modification

Question 25

What are the roles of the SER?

Answer 25

Lipid synthesis it also produces steroid hormones, and assists detoxification.

Question 26

What is the fluid in the cytoplasm?

Answer 26

Cytosol

Question 27

What are the three main roles of the cytoskeleton?

Answer 27

Movement: Cell motility Cellular organisation: Moving organelles around a cell, vesicle transport for secretion. Structure: Mechanical strength

Question 28

What are the three major protein filaments of the cytoskeleton?

Answer 28

Microfilaments Intermediate filaments Microtubules

Question 29

What is the diameter of microfilaments?

Answer 29

5-7nm

Question 30

What is the diameter of intermediate filaments?

Answer 30

10-12nm

Question 31

What is the diameter of microtubules?

Answer 31

25nm

Question 32

What is the most notable microfilament?

Answer 32

Actin

Question 33

Where are actin microfilaments concentrated?

Answer 33

Just below the cell membrane

Question 34

What is meant by microfilament polarity, what is different at each end?

Answer 34

A plus end where growth and shrinkage are fast and a minus end where they are slow

Question 35

How do actin filaments determine cell shape and movement?

Answer 35

Depolymerising and polymerising at the ends

Question 36

How does actin determine cell movement (muscle in particular)?

Answer 36

Actin binding site forms a cross-bridge with the myosin head that leads to a power-stroke.

Question 37

What proteins make microtubules?

Answer 37

Alpha and beta tubulin

Question 38

Where do microtubules originate from?

Answer 38

Microtubule organising centre (MTOC).

Question 39

What are the roles of microtubules?

Answer 39

Positions organelles, aids cell division and intracellular transport

Question 40

What does the MTOC contain?

Answer 40

Two cylindrical shaped centrioles

Question 41

Where do centrioles move in cell division?

Answer 41

To poles

Question 42

Which end of the microtubule is embedded in the MTOC?

Answer 42

- end

Question 43

Which end of the microtubule grows/shrinks faster?

Answer 43

+ end

Question 44

What molecules favour growth and shrinkage of MT?

Answer 44

GTP favours growth, GDP favours shrinking

Question 45

What is the name of proteins that move along MT?

Answer 45

Motor proteins

Question 46

What do motor proteins require to move along MT?

Answer 46

ATP

Question 47

What are the two key motor proteins and what direction does each one move cargo?

Answer 47

Kinesin moves from the MTOC to the plus end, dynein moves from the plus end to the minus end.

Question 48

What is the role of MAPs?

Answer 48

Microtubule associated proteins (MAPs) bind the stabilise longer microtubules to encourage growth at the plus end.

Question 49

What is the main role of intermediate filaments?

Answer 49

Maintain mechanical strength and structure

Question 50

What are key examples of intermediate filaments?

Answer 50

Neurofilament, keratin and nuclear laminin proteins.

Question 51

What holds keratin filments in place (2)?

Answer 51

Disulfide bond crosslinks as a result of many cysteine residues Hemidesmosomes (basal lamina to cell)

Question 52

What are the three main types of cell junction?

Answer 52

Anchoring Occluding (tight) Gap

Question 53

What filaments underpin anchoring junctions?

Answer 53

Intermediate filaments

Question 54

What are the three subcategories of anchoring junctions?

Answer 54

Desmosomes (cell to cell) Hemidesmosome ( cell to basal lamina) Adherens (cell to cell)

Question 55

What intermediate filaments underpin anchoring junctions in epithelia?

Answer 55

Keratin

Question 56

What intermediate filaments underpin anchoring junctions in cardiac cells?

Answer 56

Desmin

Question 57

What are adherens, why are they different to desmosomes?

Answer 57

Cell to cell adhering junction Connect actin filaments not intermediate

Question 58

What is the role of tight junctions?

Answer 58

Dynamic seal that adjusts intercellular permeability acting as a barrier to harmful contents

Question 59

What are the tight junction proteins?

Answer 59

Claudin and occludin

Question 60

Describe the structure of a gap junction

Answer 60

6 transmembrane connexin proteins makes up a connexon complex

Question 61

What is the function of gap junctions?

Answer 61

Couple cells chemically and electrically

Question 62

What are several junctions that are important in tight epithelia?

Answer 62

Junctional complex Zonula occludens Zonula adherens Macula adherns

Question 63

Site for activation of sugars for oxidation

Answer 63

Cytoplasm