Week 3 - molecules

Question 1

stem cell differentiation

Answer 1

asymmetric division - produce one identical daughter cell and one second daughter cell with different genetic instructions (will become a progenitor or precursor cell)

Question 2

cell potency

Answer 2

cells ability to differentiate into other types of cell - more cells it can differentiate into, the greater its potency

Question 3

four types of cell potency

Answer 3

totipotent - any cell type of adult body and embryonic membrane
pluripotent - any cell type in adult body
multipotent - tissue-specific cell type of adult body
unipotent - one specific type of adult body tissue cells

Question 4

hierarchy of a stem cell potency using haematopoeitic stem cells as example

Answer 4

fertilised egg - totipotent stem cells - blastocyst containing pluripotent stem cells - haematopoeitic stem cells - blood cells

Question 5

haematopoeitic stem cells

Answer 5

generate blood and immune cells
found in bone marrow
can self renew
can differentiate into RBCs, WBCs and platelets

Question 6

what are induced pluripotent stem cells

Answer 6

adult somatic SCs that have been reprogrammed back to pluripotency - meaning they can be turned back to SCs and differentiate into other cell types

Question 7

how to make induced pluripotent stem cells

Answer 7

Treated with transcription factors (OCT-3/4, SOX2, c-Myc and KLF4) to switch on genes to induce and maintain pluripotency

Question 8

describe iPSCs

Answer 8

stem cells markers 
self-renewal capability 
differentiation potential 
the ability to be cultured (grown in lab)
the ability to form all the germ layers

Question 9

where are human embryonic stem cells derived from

Answer 9

inner cell mass of blastocyst

Question 10

cons of using adult stem cells instead of embryonic SCs

Answer 10

more difficult to isolate them as there is few in number and it is difficult to keep them proliferating in culture

Question 11

theory of cancer stem cells

Answer 11

stem-like cells within tumours
exhibit characteristics of both SCs and cancer cells
Defined by ability to generate more stem cells (self-renewal) and to produce cells that differentiate
Have ability to seed tumours when transplanted into an animal host

Question 12

stem cell potential uses

Answer 12

tissue repair
drug screening 
vehicles for gene therapy 
regenerative medicine (bone marrow transplants and HoloclarR)
develop cartilage treatment 
current research into making new blood

Question 13

examples of adult tissue stem cells and their function

Answer 13

haemopoeitic stem cells generate blood and immune cells

mesenchymal stem cells can make different cells belonging to skeletal tissues

Question 14

genome

Answer 14

complete set of genetic instructions

Question 15

transcriptome

Answer 15

complement of genes that are actually transcribed

Question 16

housekeeping genes

Answer 16

genes transcribed in every cell type

Question 17

do all cells transcribe the same genes

Answer 17

Different cells transcribe different subsets of genes, and it’s a subset of genes that you transcribe into message RNA that starts to give the cell its identity or it’s phenotype

Question 18

proteome

Answer 18

entire set of proteins that can be expressed by a genome

Question 19

amino acid structure

Answer 19

Amine group and carboxyl group
R is a variable chemical group
Link up via a condensation reaction – water is removed from amino acids and they join as a peptide bond

Question 20

examples of post-translational modifications of proteins

Answer 20

Many proteins are glycosylated - help interacting with partner proteins, protect them, increase half life, important for orientation
Many are phosphorylated – receptor signalling, intracellular communication, control of enzyme function

Question 21

to begin translation, how does the ribosome know which methionine to bind to

Answer 21

little sequences of bases called kozak sequnces help – when ribosome sees kozak sequence that tells ribsome the next methionine codon is the start

Question 22

locations of protein synthesis

Answer 22

Smooth ER involved in lipid synthesis and metabolism
Rough ER involved in protein secretion
translate the protein in the centre of the endoplasmic reticulum and then the proteins, bud off into little vesicles, they can get decorated in the Golgi apparatus and then they could be secreted by fusing with the membrane
Soluble intracellular proteins are synthesised by free ribosomes

Question 23

how do newly synthesised proteins know where to go

Answer 23

they carry amino acid sequences (signals) that tell them where to go
signal peptides is used for entry into ER and a nuclear translocation signal is used for proteins going to the nucleus

Question 24

explain what is meant by the four different protein structures

Answer 24

primary structure - amino acid sequence
secondary - amino acids folded into structures such as alpha helixes or beta pleated sheets
tertiary - proper folding of protein into final shape
quartenary - coming together of subunits to form the overall functional protein

Question 25

diseases caused by protein mutations

Answer 25

sickle cell anemia - Mutation in the beta-globin gene - 1 codon changes – valine is coded for instead of glutamic acid - Changes the whole structure of protein
cancer - RAS can become hyperactive

Question 26

haemostasis

Answer 26

the stopping of blood flow which helps to prevent blood loss

Question 27

three phases of haemostasis

Answer 27

vasoconstriction
formation of a platelet plug
coagulation

Question 28

haemophilia

Answer 28

patients lack a clotting factor which leads to impaired ability to form blood clots

Question 29

vasoconstriction

Answer 29

blood vessels narrow to reduce blood flow to the injured area

Question 30

formation of a platelet plug

Answer 30

Disruption to the endothelium activates platelets (bc collagen is exposed)
Activation of platelets results in a shape change and also results in the release from secretory granules - released products make platelets sticky
sticky activated platelets attract one another and adhere forming a clump

Question 31

what is essential for the intrinsic and extrinsic pathway

Answer 31

calcium

Question 32

coagulation process (final common pathway)

Answer 32

extrinsic and intrinsic result in prothrombinase activating prothrombin to form thrombin
thrombin facilitates formation of insoluble fibrin from soluble fibrinogen - leads to gel like consistency of clot - lattice of fibrin forms which traps blood cells and forms a soft clot
cross links form between fibrin strands which leads to a more stable hard clot

Question 33

fibrinolysis

Answer 33

plasminogen circulates in plasma and as clot forms it becomes trapped - it is activated by a serine protease called tissue plasminogen activator (tPA) - tPA converts plasminogen to plasmin which then breaks down the fibrin mesh

Question 34

components of blood

Answer 34

RBCs, plasma, platelets, WBCs

Question 35

function of RBCs

Answer 35

carries oxygen from lungs to systemic tissues, carries carbon dioxide from tissues to lungs
assists in the buffering of acids and bases

Question 36

structure of RBCs and how it relates to their function

Answer 36

biconcave shape maximises surface area to volume ratio to maximise O2 exchange
flexible and has a bell shape so it can pass through small blood vessels
no nucleus to maximise space for oxygen
Deoxy-haemoglobin has a relatively low affinity for oxygen, but when one molecule binds to a single heme, the oxygen affinity increases, allowing the second molecule to bind more easily, etc.

Question 37

function of platelets

Answer 37

small cell fragments that are essential component of coagulation system

Question 38

function of plasma

Answer 38

fluid that carries blood components throughout body - delivers nutrients, hormones and proteins to parts that need it
helps remove waste from the body

Question 39

differences between the intrinsic and extrinsic pathway

Answer 39

intrinsic is slower and involves more steps

extrinsic is initiated by tissue factor and intrinsic is initiated by activated platelets