Proteoglycans and glycoproteins

Question 1

What are glycoconjugates?

Answer 1

conjugate molecules of carbs + other molecules such as proteins and lipids

Question 2

Glycoconjugate Classes

Answer 2

proteoglycans
glycoproteins
glycolipids

Question 3

Functions of glycoconjugates

Answer 3

communication between cells and their extracellular surroundings

Question 4

Name the 6 specific functions of glycoconjugates

Answer 4

1. mediators of specific cell-cell interaction
2. mediators of interaction between cell and ECM
3. cell-cell recognition
4. adhesion
5. immune response
6. wound healing

Question 5

What are proteoglycans?

Answer 5

macromolecules of the cell surface of ECM

- 1 or more sulfated glycoaminoglycan chains are joined covalently to a membrane protein or a secreted protein

Question 6

Glycosaminoglycans are ____________ of the extracellular matrix

Answer 6

heteropolysaccharides

Question 7

How does the glycosaminoglycan chain bind to extracellular proteins?

Answer 7

through electrostatic interactions between the protein and the negatively charged sugar moieties on the proteoglycan

Question 8

Proteoglycans are major components of

Answer 8

all extracellular matrices

Question 9

Mammalian cells can produce at least

Answer 9

40 types of proteoglycans

Question 10

Proteoclycans act as ______ ________, and they influence various cellular activities, such as ________ _______ ______ and ________.

Answer 10

tissue organizers, growth factor activation, adhesion

Question 11

Most proteoglycans are secreted into the ____.

However, some are ____ _____ ______.

Answer 11

ECM

integral membrane proteins

Question 12

Proteoglycans are major components of ______ ______ such as ________.

Answer 12

connective tissues

cartilage

Question 13

What does the basic proteoglycan unit consist of?

Answer 13

a ‘core protein’ with covalently attached glycosaminoglycans

Question 14

The point of attachment is a ___ _______, to which the glycosaminoglycan is joined through a __________ ______.

Answer 14

ser residue

tetrasaccharide bridge

Question 15

What are smaller oligsaccharides usually attached to?

Answer 15

the core protein near its site of attachment to hyaluronate

Question 16

Some proteoglycans can form

Answer 16

proteoglycan aggregates

Question 17

What are proteoglycan aggregates?

Answer 17

enormous supramolecular assemblies of many glycosaminoglycan-decorated core proteins all bound to a single molecule of hyaluronan

Question 18

What core protein is usually involved?

Answer 18

aggrecan

Question 19

What does aggrecan do?

Answer 19

it binds multiple chains of chondroitin sulfate and keratin sulfate via covalent linkages to serine residues

Question 19

Aggrecan interacts with ______ in the ECM of ______, contributing to the development, _____ strength, and resilience of this connective tissue.

Answer 19

collagen, cartilage, fensile

Question 20

What is the ECM?

Answer 20

a strong and resilient meshwork containing proteoglycans in association with collagen, elastin, and fibronectin

Question 21

What are glycoproteins?

Answer 21

Glycoproteins have 1 or several oligosaccharides of varying joined covalently to a protein

Question 22

Where are glycoproteins?

Answer 22

usually found on the outer face of the plasma membrane

• ECM
• in the blood

Question 23

Where are glycoproteins found inside cells?

Answer 23

they are found in specific organelles such as golgi complexes, secretory granules, and lysosomes

Question 24

Glycoproteins are

Answer 24

carb-protein conjugates in which the glycans are branched +smaller + more structurally diverse than the huge glycosaminoglycans of proteoglycans

Question 25

What are 2 classes of glycoproteins that occur in nature?

Answer 25

O-linked and N-linked glycoproteins

Question 26

O-linked glycoproteins

Answer 26

the carb is attached at its anomeric carbon through a glycosidic linkage to the -OH group of a ser or Thr residue

Question 27

N-linked glycoproteins

Answer 27

the carb is attached via an N-glycosyl linkage to the amide nitrogen of an Asn residue of the protein

Question 28

About half of all proteins of mammals are

Answer 28

gllycosylated

Question 29

What are examples of glycosylated secretory proteins?

Answer 29

immunoglobulins (antibodies)
certain hormones (follicle-stimulating hormones and luteinizing hormone)

Question 30

What are biological advantages of protein glycosylation?

Answer 30

improving the solubility of proteins
providing address labels directing targeting in cells and between tissues
protein folding
stabilization

Question 31

In glycolipids and lipopolysaccharides, complex oligosaccharide chains are

Answer 31

attached to membrane-anchored lipid moieties

Question 32

Plants and animals contain many types of

Answer 32

glycolipids and glycosphingolipids

Question 33

What are gangliosides?

Answer 33

glycosphingolipids w/ complex oligosaccharide chains w/ sialic acid residues

Question 34

What are gangliosides important for?

Answer 34

cell-cell recognition

some serve as receptors for the entry of bacterial toxins such as cholera toxin into mammalian cells

Question 35

Other glycosphingolipds, the _______, contain oligosaccharide chains that serve as the ______ _______ ________.

Answer 35

globosides, blood group antigens