Organelles Self-study

Question 1

Phospholipids

Answer 1

• Found in cell membranes - Glycerol molecule with two fatty acid chains and one phosphate containing side group attached - forms the lipid bilayer - Amphipathic – having both hydrophilic (head) and hydrophobic (tail) domain in the same molecule

Question 2

Neutral lipids

Answer 2

• Found in cell membranes - Primarily cholesterol and cholesterol esters - Important for control of membrane fluidity

Question 3

Glycolipids

Answer 3

• Found in cell membranes - Glycerol chain with two fatty acid chains and one carbohydrate group attached - Most important as antigens or membrane recognition molecules

Question 4

Where are phospholipids synthesized?

Answer 4

on the endoplasmic reticulum membrane

Question 5

Integral membrane proteins

Answer 5

• Proteins embedded in the lipid bilayer - They may span entire bilayer in one-pass or multi-passes - May be embedded in just the outer or inner portion - Some are glycoproteins with an attached carbohydrate chain on the outer cell surface.

Question 6

Peripheral membrane proteins

Answer 6

Protein closely associated with the inner surface of the membrane by interaction with membrane lipids, integral membrane proteins or both

Question 7

Zonula Occludens

Answer 7

• tight junctions - closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier to fluid

Question 8

Zonula Adherens

Answer 8

protein complexes that occur at cell–cell junctions in epithelial and endothelial tissues, usually more basal than tight junctions

Question 9

Desmosomes

Answer 9

• also macula adherens - they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes - anchors cells to adjacent cells to maintain tissue integrity

Question 10

Gap junctions

Answer 10

• Bridges the space or gap between cells - allows molecules, ions, electrical impulses to pass through regulated gates between calls - They are arranged in arrays to form channels

Question 11

The nucleus is lined by …., called the …

Answer 11

The nucleus is lined by fibrous meshwork, called the nuclear lamina.

Question 12

Nuclear Pore Complex formed by specific proteins that …

Answer 12

Nuclear Pore Complex formed by specific proteins that regulate movement of material (RNAs, proteins and ribosome subunits) in and out of nucleus.

Question 13

In the Nuclear Pore Complex, proteins are carried in via binding to a carrier protein called …

Answer 13

In the Nuclear Pore Complex, proteins are carried in via binding to a carrier protein called importin.

Question 14

Chromatin is organized as …

Answer 14

euchromatin and heterochromatin

Question 15

Heterochromatin

Answer 15

• condensed chromatin (tightly packed DNA) - transcription inactive - located peripherally in the nucleus

Question 16

Euchromatin

Answer 16

• extended chromatin - transcriptionally active - makes up 92% of chromatin

Question 17

Functions of the nucleus

Answer 17

1. transmission of genetic material from generation to generation 2. transcription of RNA 3. Formation of ribosomes

Question 18

Structure of Golgi Apparatus

Answer 18

• stack of membrane bound disc shaped cisternae - cis face - entry face. Closely associated with RER - Trans face - exit face. Closely associated with trans network

Question 19

Trans golgi network

Answer 19

interconnected membrane bound vesicles directing material to various locations in the cell after leaving the Golgi Apparatus

Question 20

Structure of mitochondria

Answer 20

tubular or sausage shaped structures with a double membrane

Question 21

The outer membrane of mitochondria is

Answer 21

highly permeable

Question 22

The inner membrane of mitochondria is …. forming ….

Answer 22

highly folded, cristae

Question 23

Myosins are …

Answer 23

• family of ATP-dependent motor proteins - known for their role in muscle contraction

Question 24

Extracellular Matrix (ECM)

Answer 24

-a collection of extracellular molecules secreted by cells that provides structural and biochemical support to the surrounding cells - consists of ground substance and fibers

Question 25

Ground substance (ECM)

Answer 25

amorphous and couscous intercellular mixture of proteoglycans, structural glycoproteins, and tissue fluid

Question 26

Glycosaminoglycans (GAGs)

Answer 26

- found in ground substance of ECM - long, unbranched molecules composed of disaccharides, with an amino group (sulphated) and glucohyaluronic acid - the negative charge attracts cations, which attract water (hydrophilic) to help resist compression forces

Question 27

Proteoglycans (in ground substance)

Answer 27

- a very large molecule which consists of GAGs bound covalently to a protein core, which is in turn, attached via a link protein to hyaluronic acid - Proteoglycans provide a gel state in the ECM and also provide some of its barrier functions - location: basement membranes, eye, skin, blood vessels, and cartilage

Question 28

Structural glycoproteins (found in ground substance) are molecules that bind ... They are involved in cell ...

Answer 28

Structural glycoproteins (found in ground substance) are molecules that bind cells to the ECM. They are involved in cell adhesion and migration.

Question 29

fibronectin

Answer 29

- glycoprotein - derived from fibroblasts - binding sites on cell surface, in basement membrane, along collagen fibers, chemotactic

Question 30

laminin

Answer 30

- glycoprotein - derived from epithelial cells - found in the basal lamina - binds type IV collagen

Question 31

chondronectin

Answer 31

- glycoprotein - derived from chondrocytes - found in cartilage - binds to type II collagen

Question 32

osteonectin

Answer 32

- glycoprotein - found in bone - associated with type I collagen

Question 33

Tissue fluid in ground substance

Answer 33

- similar to and derived from the blood plasma - bound to the negatively charged GAGs - transports nutrients and wastes by hydrostatic and osmotic pressure 

Question 34

reticular fibers

Answer 34

- type III collagen - thinner fibrils - located in smooth muscle, nerve

Question 35

Epithelial tissue may be derived from all three embryonic germ layers (.....). However, most epithelia are derived from the ... and ....

Answer 35

Epithelial tissue may be derived from all three embryonic germ layers (ectoderm, endoderm and mesoderm). However, most epithelia are derived from the ectoderm and endoderm.

Question 36

The epithelium is attached to ....

Answer 36

the basal lamina

Question 37

The basal lamina is produced by

Answer 37

epithelial cells

Question 38

Epithelial cells are ...., they receive ... via blood vessels in the underlying ....

Answer 38

Epithelial cells are avascular, they receive nutrients, O2 via blood vessels in the underlying connective tissue.

Question 39

Stratified epithelium are classified according to the morphology of the ...

Answer 39

apical cell layer

Question 40

Glycocalyx

Answer 40

In the cell membrane, the carbohydrate-rich region of glycolipids is referred to as the glycocalyx