Test 3. Lecture 26

Question 1

choloroplasts are a type of __________.

Plastids have the same genome as chloroplasts, but differ in structure and
function.
Chloroplasts are specialized for photosynthesis; other plastids are involved in
other aspects of plant metabolism.
Other plastids have a double-membrane envelope but lack thylakoid membranes
and other components of the photosynthetic apparatus.

Answer 1

plastid

Question 2

plastid are classified based on the pigments they contain

_______ contain chlorophyll
________ contain carotenoids, resulting in yellow, orange, and red color of flower and fruits

____________ store A VARIETY OF ENERGY sources in nonphotosynthetic tissues

______ and __________ are leucoplasts that STORE STARCH AND LIPIDS

Answer 2

chloroplast

chromoplasts

leucoplasts

amyloplasts and elaioplasts

Question 3

1. All plastids develop from ___________ , small undifferentiated organelles in rapidly dividing cells
2. some mature plastids can change from one type to another. Chromoplasts develop from chloroplast during fruit ripening
3. Devlopment of plastids is controlled by
   ______________-
   _____________
4. in the photosynthetic cells of leaves, protplastids develop into chloroplasts in the prescence of light

Answer 3

proplastids

environmental signals
intrinsic developmental signals

Question 4

if kept in the dark, development of protoplastids is arrested at an intermediate stage (_____________)

an array of tubular interal membrane has formed, bu chlorophyll has not been synthesized

if moved into the light, etioplasts devlop into choloroplast

Answer 4

etioplasts

Question 5

_______________: SINGLE-MEMBRANE - enclosed organelles containing enzymes involved in many metabolic reactions

Answer 5

peroxisomes

Question 6

peroxisomes do not have their own ____________

most peroxisomal proteins are synthesized on free ribosomes and imported as completed polypeptides

Answer 6

genomes

Question 7

perioxomes can replicate by division but can also be regenerated even if entirely lost

Peroxins are typical eukaryotic proteins ( many mitochondrial and plastid proteins resemble those of prokaryotes)

________________ are broken down by ___________ reactions in peroxisomes, which leads to the production of HYDROGEN PEROXIDE

Answer 7

many substance

oxidative reactions

Question 8

_________________ converts hydrogen peroxide to water or uses i to oxidize another organic compound

Answer 8

catalase

Question 9

1. Peroxisomes are also involved in synthesis of lipids

In animal cells, ____________ and ______________ are synthesized in peroxisomes and in the eR.

In the liver, peroxisomes are involved n synthesis of bile acids from cholesterol

peroxisome have enzymes for synthesize of _________-_________ with one hydrogcarbon chain joined to glycerol by an ether bond rather than an ester bond

plasmalogens are important membrane components in some tissues

Answer 9

In animal cells, cholesterol and dolichol are synthesized in perosomes and in the ER

peroxisomes have enzymes for synthesis of plasmalogens-phospholipids

Question 10

In seeds, peroxisomes convert fatty acids to carbohydrates via the _______________ ( variant of the CAC)

THis provides energy and raw materials for the germinating plant

the peroxisomes are sometimes called __________-

Answer 10

glyoxylate cycle

glyoxysomes

Question 11

Cytoskeletons (general information?)

Answer 11

The cytoskeleton is a network of protein filaments extending throughout the
cytoplasm of eukaryotic cells.

• It provides a structural framework that determines cell shape, positions of
organelles, and general organization of the cytoplasm.

• The cytoskeleton is also responsible for movement of entire cells, and internal
transport of organelles and other structures.

• It is not rigid, but is a dynamic structure that is continually reorganized as cells
move and change shape.

Question 12

the cytoskeleton is composed of three main types of protein filaments?

____ polymerizes to form actin filaments (_________)

Answer 12

1. actin filament
2. microtubules
3. intermediate filaments

ACTIN polymerizes to for actin filaments (MICROFILAMENTS)

Question 13

________________regulate assembly and disassembly of actin
filaments, cross-linking into bundles and networks, and associations
with other cell structures.

Answer 13

actin-binding proteins

Question 14

 All the actin monomers are oriented in the same direction, so actin
filaments have ________.
 This is important in their assembly and in establishing the direction of
myosin movement relative to actin.
 __________is the first step of actin polymerization—a trimer is formed, and
monomers are then added to either end.
 Actin polymerization is _______; the filaments can be broken down when
necessary.

Answer 14

• polarity
• nucleation
• reversible

Question 15

Actin is very abundant (5 to 10% of total protein) in all types of eukaryotic cells.
Mammals have______ genes: 4 are expressed in ________ cells and 2 in ______

Answer 15

• 6 actin genes
• 4 expressed in MUSCLE CELLS
• 2 in NONMUSCLE CELLS

Question 16

Each actin monomer (________) has tight binding sites that mediate head-to-tail
interactions with two other actin monomers, to form filaments (____________).

Answer 16

globular [G] actin

filamentous [F] actin

Question 17

TREADMILLING:

The barbed end of a filament grows 5–10 times faster than the pointed end.
Actin bound to ________ associates with _______, and the ATP is then hydrolyzed
to ADP.
______is less tightly bound than ATP-actin and ______________
Treadmilling is critical in regulating actin filaments within the cell.

Answer 17

ATP

the barbed ends

ADP-actin

dissociates at the pointed end.

Question 18

Actin-binding proteins: (KNOW)

_________ bind ATP-actin and nucleate INITIAL POLYMERIZATION of long
unbranched actin filaments.

_________ binds actin monomers and stimulates EXCHANGE OF BOUND ADP for ATP, increasing the local concentration of ATP-actin.

Answer 18

FORMINS

PROFILINS

Question 19

(KNOW)
______________(actin-related proteins): initiate growth of branched actin
filaments, important in driving cell movement at the plasma membrane

Answer 19

Arp2/3 complex

Question 20

(KNOW)
_____________ stabilize actin filaments by binding lengthwise along the
groove of the filament.
Capping proteins stabilize actin by binding to the barbed or pointed ends

Answer 20

Tropomyosins

Question 21

(KNOW)
Other actin-binding proteins remodel or modify existing filaments.
_______________ severs filaments, generating new ends which are then available for
polymerization or depolymerization.

Answer 21

Cofilin

(The actin-binding proteins act together to promote rapid turnover of filaments and
remodeling of the cytoskeleton needed for cell movements and changes in cell shape.
Their activities are controlled by signaling mechanisms in response to environmental
signals.)