Cell biology 2

Question 1

What is connective tissue? What does it consist of?

Answer 1

Tissues that lies between two other tissues. Consist of extracellular matrix and cells

Question 2

What are the different categories of connective tissue? Give examples for each category

Answer 2

Loose connective tissue: Serous membrane Adipose Blood Dense connective tissue: Dermis of the skin Bone and cartilage

Question 3

Which cells can be found in connective tissue? Where are they synthesised?

Answer 3

•Fibroblast • Adipocytes-fat • Chondrocytes-Cartilage • Osteocytes-Bone • Haemopoietic (blood) cells Synthesised in extra cellular matrix

Question 4

What is categorised as the Extracellular Matrix? What is the Extracellular Matrix’s function?

Answer 4

Material outside the cell is the ECM The ECM determines a tissues physical properties It is also involved in cell migration, shape, proliferation and survival

Question 5

What are the two main types of macromolecules found in the ECM?

Answer 5

1. Polysaccharide chains called glycosaminoglycans, (GAGs), usually linked to a protein - proteoglycans (gel in which cells and fibrous proteins are embedded ) 2. Fibrous proteins – collagen, elastin, fibronectin (structure, strength, flexibility, adhesion, cell positioning)

Question 6

Where are proteoglycans produced? How do they enter the ECM?

Answer 6

Production- ER and Golgi Delivery-constitutive secretion

Question 7

How are proteoglycan gels produced?

Answer 7

When proteoglycans combine with water

Question 8

Name 2 main functions of GAG & proteoglycan gels

Answer 8

1. Resist compression 2. Permit rapid diffusion of nutrients, hormones and metabolites

Question 9

List the 4 main groups of GAG’ s and describe what each group does

Answer 9

1. Heparin sufate- cell adhesion, regulation of cell proliferation, cancer metastasis 2. Chondroitin sulfate/dermatan sulfate- migration for wound repair Inhibition of axonal growth brain development, 3. Keratan sulfate- Within cornea Anti-adhesive (cell motility) 4. Hyaluronic acid Component of synovial tissues and fluid Lubricant- resists compression

Question 10

How are Proteoglycans formed? Give examples of 3 different kinds

Answer 10

One or more glycosaminoglycan (GAG) chains attached to a core protein.

1. Aggrecan
2. biglycan
3. Syndecan

Question 11

Describe the sturcture, distribution and abundance of collagen

Answer 11

Amino acids which form elongated fibrils

Mostly found in fibrouse tissue- tendons, ligaments and skin

The most abundant protein

Question 12

Describe the 5 most common types of collagen

Answer 12

Type 1- (most abundant)- skin, tendons, organs, bones

Type 2- Cartilage

Type 3- Retinaculate (spleen liver bone marrow)

Type 4- basila lamina (found alonside type 1)

Type 5- cell surfaces, hair and placenta- diameter of type 1

Question 13

Describe the sturcture and function and distribution of elastin

Answer 13

Structure- Associated with fibrillin and rich in the amino caids- glycine and proline

Function- Forms the main component of elstaic conncetive tissue. Found most in the dermis if the skin and arteries

Question 14

What is marphan syndrome?

Answer 14

Mutation in fibrillin gene

Effects conncetive tissue rich in elsatic fibers

severe case- Aorta is prone to rupture

Question 15

Describe the sturcture and function of Fibronectin

Answer 15

Structure- glycoprotein dimer

Function- Binds to intergrins, involved in cell adhesion, growth mibration and differentiation

Binds to collagen

Extracellular matrix is connected to the inside of the cell by fibronectin. Collagen signals tension, and initiates cell activation or deactivation

Question 16

Describe the structure and function of the basal lamina

Answer 16

Structure- layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits

Made of type 4 collagen, heparun sulfate, laminin, nidogen

Has 2 layers- lamina densa and lamina lucida

Function- provides sturctural support, relays messages, separates epithelial cells from the underlying connective tissue and supports, anchors, protects, selective cell movement, molecular filtering, and signaling.

Question 17

The ECM and cancer

Answer 17

Tumour invasion involves the desctruction of ECM and basal lamina by enzymes enbaling the cell to enter the blood stream and surrounding tissues

Question 18

List the different types of epthilial junctions

Answer 18

Tight junctions

Adherens junctions

Desmosome junctions

Gap junctions

Hemidesmosome junctions

Question 19

Function of tight junctions? What happens in a diseased state?

Answer 19

Holds cells together

Maintain osmotic balance and used in material trasport

prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells, so materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue.

Diseased- Viruses and bateria can effect tigh junction and functions

Altertaions in expresion of tigh junction proteins has been found in nuerological disorders e.g. multiple sclerosis, stroke, Alzheimer’s disease, Parkinson’s disease and epilepsy.

Question 20

Function of desmosomes junctions? What happens in a diseased state?

Answer 20

Cells in tissues are joined by desmosomes

They connect intermidiate filaments in one cell to those in the next

Occure in the lateral side of plasma membarnes

Found in tissues with insense mechnical stress e.g. cardica muscle

Diseased state- causes compromised cutaneous and/or cardiac function, cardomyopthay

Can be broken down by autoantibdoies leading to fluid accumilation and blisteres of the skin. Pemphigus vulgaris.

Question 21

Function of Adherens junctions and manigestations in a diseased state

Answer 21

Connects actin filaments in adjacent cells

They support both strong cell–cell adhesion and rapid cell–cell contact remodeling during development and wound healing

Diseased state- contributes to endothelial dilator dysfunction in arteries

Question 22

Function of gap junctions

Answer 22

Directly connect the cytoplasm of two cells

Allows passage of small water solubale molecules from cell- cell

Play a vital role in electrical conduction of cardiac muscles

Composed of connexin proteins which form channels

Question 23

Key features of neural synapses

Answer 23

Proteoglycans in the ECM regulate synapse formation and synaptic plasticity.

CNS synapses lack Basement membranes,

Question 24

Structure and function of Pseudopodia

Answer 24

Temporary cytoplasm-filled projection of an eukaryotic cell membrane

Used for motility or ingestion

extend and contract by the reversible assembly of actin subunits.

cell surface projects lamellipodium, Cytoplasm flows into the lamellipodium, forming the pseudopodia.

Question 25

Structure and function of Lamellipodia and Filopodia

Answer 25

Broad flat protrusions which surge forward and adhere to surfaces, allowing cells to gain traction and move

filopodia extend several micrometers ahead of the cells, explore extracellular surfaces, sense guiding cues, and direct the rest of the cell. There is abundant filopodia in invasive cancer cells

Extension of both lamellipodia and filopodia is powered by polymerization of actin into filaments by ATP

Question 26

Structure and function of Microvilli

Answer 26

• cell surface extension of secretory and absorptive epithelia
• Increase the surface area of cells by approximately 600 fold, for absorption and secretion. Digestive enzymes (glycosidases).

Conatin enzymes on surface- e.g hydrolyze carbohydrates

Question 27

What is the effect of toxins on microvillie?

Answer 27

cause destruction of intestinal microvilli and intestinal tight junctions resulting in inhibition of water-reabsorption.

Question 28

What is the effect of infection on microvillie

Answer 28

E.coli infections enabled by- Celiac disease, Microvillus Inclusion Disease

consequence

–Malabsorption of nutrients and persistent osmotic diarrhoea, often accompanied by fever, and a failure to thrive. Classic symptoms include gastrointestinal problems such as chronic diarrhoea, abdominal distention, malabsorption, loss of appetite.

Question 29

Structure and function of cilia? List condistions in the case of genetic defects

Answer 29

There are two types of cilia: motile cilia and nonmotile.

Non-motile cilia are found on nearly all cells as sensory antennae, chemosensors, photosensors, mechanosensors; signallers.

Motile cilia are usually present on a cell’s surface in large numbers and beat in coordinated waves e.g., in the trachea or fallopian tubes.

genetic ciliopathies eg. - Bardet–Biedl Syndrome; polycystic kidney disease; lack of cilia in fallopian tubes – ectopic pregnancy