Overview of mammalian cell function

Question 1

Disease

Answer 1

Any condition (other than a disability) in which the normal structure or functions of the body are damaged or impaired

Question 2

Infectious disease

Answer 2

When the damage is the result of an infection by disease-causing (micro) organisms

Question 3

Necessary Cellular functions

Answer 3

1) Protection from the external environment
2) Nutrient acquisition
3) recycling of cell components
4) Communication
5) Energy generation
6) Anabolism

Question 4

Plasma membrane

Answer 4

Encloses the cell
Defines its boundaries
Acts as a selective barrier between the cytosol and external environment

Question 5

Inside cell membranes

Answer 5

Inside the cell, the membranes of organelles separate the contents of the organelle from the cytosol

Question 6

Properties of all cell membranes

Answer 6

They are dynamic fluid structures consisting of phospholipid bilayers and proteins which are non-covalently associated
They are largely impermeable to water and water soluble molecules

Question 7

Transmembrane protein functions

Answer 7

-Transport
-Communication with the outside environment
-Connection to other cells and extracellular environment
-external environment

Question 8

Importance of membrane asymmetry

Answer 8

-membranes contain varying lipid components on their inner and outer leaflets
-This is NB for membrane protein function since different proteins interact with different phospholipid head groups
-It is also important for cell signaling molecules

Question 9

2 Major classes of transport proteins

Answer 9

Transporters and channel proteins
They facilitate the movement of polar molecules across membranes

Question 10

Channels

Answer 10

Weak interactions with molecules or ions through pores such as aquaporins

Question 11

Transporters

Answer 11

Transporters undergo conformational change upon ligand binding which allows for transport

Question 12

Types of Endocytosis

Answer 12

1. Phagocytosis
2. Pinocytosis
3. Receptor-mediated endocytosis
4. Caveolae

Question 13

Lysosome

Answer 13

Membrane-bound heterogeneous organelles that play a vital role as catabolic sites for recycling and degradation of old cell components and waste
-They play an Nb role in scavenging metabolic building blocks that sustain essential biosynthetic reactions during starvation in a process called autophagy

Question 14

Components of lysosomes

Answer 14

They contain as many as 40 hydrolytic enzymes such as nucleases, phosphatases, lipases.
They are acid hydrolases in that they function at low pH

Question 15

Inside environment of lysosmes

Answer 15

They have a pH of 5.0 ( while the body has a pH of 7.2) which is maintained by a proton pump (vacuolar H+ ATPase) in the lysosomal membrane.

Question 16

Types of signaling

Answer 16

-Autocrine
-Paracrine
-Endocrine
-Direct
-Synaptic

Question 17

Autocrine

Answer 17

Cell targets itself

Question 18

Paracrine

Answer 18

A cell signals a nearby cell

Question 19

Endocrine

Answer 19

A cell targets a distant cell through the bloodstream

Question 20

Direct

Answer 20

A cell targets a neighbouring cell through a gap junction

Question 21

Synaptic

Answer 21

Neural cells communicate via neurotransmitters

Question 22

Two states of GTP-binding proteins

Answer 22

They have an active state and an inactive state by binding GTP (guanosine triphosphate) and GDP (guanosine diphosphate), respectively.
they have inherent GTPase activity

Question 23

GTPase activity

Answer 23

They can degrade GTP to GDP, and thus become inactive

Question 24

2 Classes of proteins regulate GTP-binding proteins

Answer 24

1) GTPase-activating proteins (GAP)
2) Guanine nucleotide exchange factors (GEFs)

Question 25

GAPs

Answer 25

-GTPase-activating proteins
-They increase the rate of GTP hydrolysis to GDP thus ‘switching off’ the G-Protein

Question 26

GEFs

Answer 26

-Guanine nucleotide exchange factors
-They facilitate the swooping of GDP for GTP in the G-Protein, resulting in its activation

Question 27

Ras class proteins

Answer 27

They are an NB class of monomeric GTPases (GTP-binding proteins) involved in important signalling pathways
-They exist as K, H and N-Ras
-They work downstream of a class of receptors called Receptor Tyrosine Kinases