Biosci 461 Exam 2 Notes

Front 1

What is a special form of endocytosis in which the cell uses large endocytic vesicles to ingest large particles such as microorganisms and dead cells?

Back 1

phagocytosis

Front 2

How do lower, single-celled eukaryotes use phagocytosis?

Back 2

as food by passing products of engulfment into cytosol; takes in food for cellular processes

Front 3

How do multi-cellular organism use phagocytosis?

Back 3

for defense against invading microbes and scavenging of old or damaged cells; removes debris and pathogens

Front 4

What "professional phagocytes" carry out phagocytosis in multicellular organism? and what are their functions?

Back 4

macrophages- scavenge senescent cells and death programmed cells, both neutrophils and macrophages are used for defense by ingesting microorganisms ofr defense against infection.

Front 5

What is the process of phagocytosis?

Back 5

particles (microorganisms;microbes) bind to surface of phagocyte- requires the activation of receptors called Fc receptors- which antibodies form a tail region and a coat called the Fc region which is recognized by the Fc receptors on the surface of macrophages and neutrophils, binding induces the cell to extend pseudopods that engulf the particle and fuse at their tips to form a phagosome.
summarized: a. Ingestion through phagocytosis, a phagosome is formed
b. The fusion of lysosomes with the phagosome creates a phagolysosome; the pathogen is broken down by enzymes
c. Waste material is expelled or assimilated (the latter not pictured)

Front 6

What drives the extension of the pseudopod and the formation of the phagosome?

Back 6

actin polymerization and reognization

Front 7

What is all eukaryotic cells continually ingest bits of their plasma membrane in the form of small pinocytic vesicles, which are later returned to the cell surfac- the rate at which the plasma membrane is internalized?

Back 7

pinocytosis

Front 8

What makes phagocytosis distinct from other forms of endocytosis?

Back 8

it is a vesicular internatlization of SOLID particles

Front 9

Why are antibodies the best triggers for phagocytosis activation?

Back 9

protects us by binding to the surface of infectious microorganisms to form a coat that exposes the tail region on the exterior of each antibody molecule.
which the tail region is recongnized by the Fc receptors on the macrophages or neutrophils (phagocytes)

Front 10

What causes a response from actin polymerization and reorganization and what are their functions?

Back 10

they drive the formation of a phagosome from the extension of a pseudopod engulfing a large particle and fusing with a lysosome- acting polymerization and reorganization respond to accumulation of specific phosphoinositides

Front 11

What is the rate at which plasma membrane is internalized during this form of endocytosis?

Back 11

pinocytosis

Front 12

What is pinocytosis primarily used for?

Back 12

for the absorption of extracellular fluids (ECF),

Front 13

give examples of the varying cell types and their rates at which the internally ingest their plasma membrane?

Back 13

macrophage ingests 25% of its own volume of fluid each hour during pinocytosis (3% of plasma membrane)

Front 14

Why is pinocytosis a continuous process typically?

Back 14

because it is coupled with exocytosis which at the same time is adding back to the plasma membrane

Front 15

What are steps of pinocytosis?

Back 15

begins at clathrin coated pits of the plasma membrane that invaginate and pinches off to form a clathrin-coated vesicle- which fuse with early endosomes which take up lipoprotein particles

Front 16

Which type of cells does receptor-mediated endocytosis take place?

Back 16

animal cells

Front 17

How is cholesterol transported the blood?

Back 17

as cholesteryl esterse in the form of lipid-protein particles known as LDL's (low-density lipoproteins)

Front 18

What is the function of receptor-mediated endocytosis?

Back 18

it is widely used for the specific uptake of certain substances required by the cell;The role of receptor-mediated endocytosis is also well recognized in the downregulation of transmembrane signal transduction.The activated receptor becomes internalised and is transported to late endosomes and lysosomes for degradation. However, receptor-mediated endocytosis is also actively implicated in transducing signals from the cell periphery to the nucleus. This became apparent by the finding that the association and formation of specific signaling complexes is required for the effective signaling of hormones

Front 19

What happens when their are defective genes that encode LDL receptors?

Back 19

When individuals inherit defective genes that encode LDL’s receptors it results in high levels of blood cholesterol predispose these individuals to develop atherosclerosis prematurely, and many die at an early age of heart attacks resulting from coronary artery disease if they were not treated with drugs that lower the level of blood cholestrol.

Front 20

What is the name of this process?-After binding of a ligand to plasma membrane spanning receptors, a signal is sent through the membrane, leading to clathrin coating the membrane, and formation of a membrane invagination. The receptor, its ligand, and anything nearby are then internalised in sub-micrometre sized clathrin-coated vesicles. Once internalised, the clathrin-coated vesicle uncoats (a pre-requisite for the vesicle to fuse with other membranes) and individual vesicles fuse to form the early endosome. Since the receptor is internalized with the ligand, the system is saturable and uptake will decline until receptors are recycled to the surface?

Back 20

receptor-mediated endocytosis

Front 21

What are the steps for receptor-mediated endocytosis?

Back 21

After binding of a ligand to plasma membrane spanning receptors, a signal is sent through the membrane, leading to clathrin coating the membrane, and formation of a membrane invagination. The receptor, its ligand, and anything nearby are then internalised in sub-micrometre sized clathrin-coated vesicles. Once internalised, the clathrin-coated vesicle uncoats (a pre-requisite for the vesicle to fuse with other membranes) and individual vesicles fuse to form the early endosome. Since the receptor is internalized with the ligand, the system is saturable and uptake will decline until receptors are recycled to the surface.After shedding their clathrin coats, the vesicles deliver their contents to early endosomes located in the cell periphery- then LDL and LDL receptors encounter low pH in the endosomes and LDL is released and devivered to lysosomes.

Front 22

Which process can cause individuals to develop artherosclerosis prematurely and why?

Back 22

gene mutations that encode LDL's- receptor-mediated endocytosis

Front 23

Which process is saturable of the receptor-mediated endocytosis, phagocytosis or pinocytosis?

Back 23

receptor-mediated endocytosis

Front 24

Whichp rocess involves a receptor binding to a specific ligand in its first step?

Back 24

receptor-mediate endocytosis

Front 25

What process are these examples of LDL's receptors, transferrin and hormones?

Back 25

receptor-mediated endocytosis

Front 26

What are two differences between pinocytosis and endocytosis?

Back 26

endocytosis occurs all the time, endocytosis has internalization of membrane lipids and proteins, while pinocytosis is internalization of membrane and small fluids and can be continuous

Front 27

What is different about the LDL receptor and the transferrin receptor?

Back 27

transferrin recpeotr also recycles its ligand; avoids lysosomes and delivers iron to the cells interior.