SfM - Life at the Cellular Level

Question 1

what is a prokaryotic cell?

Answer 1

is an organism with
no nuclear membrane
no mitochondria
no membrane bound structures

Question 2

what is a eukaryotic cell?

Answer 2

any multicellular organism
nucleus w/ membrane
membrane bound structure
more complex cell membrane

Question 3

difference between multi- & pluripotent cells?

Answer 3

multipotent - cells can differentiate into many cell types of the one lineage
pluripotent - have the potential to turn into ANY cell type

Question 4

how does cancer develop?

Answer 4

cells are damaged via wear & tear/DNA damage (radiation etc), body fails to remove damaged cells

Question 5

how do tumours form?

Answer 5

mutated cells divide without any control, fail to coordinate with normal cells, fail to differentiate into specialised cells, displace and replace the normal cells = tumour

Question 6

what is apoptosis?

Answer 6

Apoptosis is a process of programmed cell death; it is an essential and central mechanism in controlling multicellular development (aims to clear damaged cells before cancer develops)

Question 7

what is the order from cells to systems?

Answer 7

cells –> tissues –> organs –> systems

Question 8

what are the 4 tissue types?

Answer 8

connective, epithelial, nervous, muscular

Question 9

what is the plasma membrane’s function?

Answer 9

transport, intercellular joining, enzymatic activity, cell-cell recognition, receptors for signal transduction, attachment to the cytoskeleton and ECM

Question 10

what are the different types of transport?

Answer 10

passive diffusion
facilitated diffusion 
endocytosis
exocytosis (constitutive/regulated)

Question 11

examples of occluding junctions?

Answer 11

tight junctions (seals gaps between epithelial cells - creates physical barrier to random diffusion)

Question 12

what are cell-cell anchoring junctions?

Answer 12

links between cells

• adherens junction (connects actin filament bundles in adjacent cells)
• desmosomes (connects keratin intermediate filaments between adjacent cells)

Question 13

channel forming junctions

Answer 13

gap junction (allows passage of small water-soluble molecules from cell to cell)

Question 14

cell-matrix anchoring junctions

Answer 14

actin-linked cell-matrix adhesion anchors
(links actin filaments in cell to ECM)
hemidesmosomes
(anchors intermediate filaments in cell to ECM)

Question 15

what happens when cell adhesion goes wrong?

Answer 15

disease occurs
in tumours they initially join together using adhesion junctions, but changes in protein expression occurs which allows the tumour to break out of cell and metastasise

Question 16

examples & definition of cell signalling

Answer 16

• contact dependent (signalling via physical contact)
• paracrine (cells release signalling molecules to cells nearby)
• endocrine (cells release hormones across a larger distance via blood)
• synaptic (specialised signalling in NS, occurs via electrical signalling causing release of neurotransmitter)

Question 17

list the cellular organelles

Answer 17

mitochondria 
nucleus 
endoplasmic reticulum (smooth and rough)
golgi apparatus 
lysosomes 
cytoskeleton 
cilia/flagella

Question 18

what is a REDOX reaction?

Answer 18

oxidation is loss and reduction is gain of electrons

• it is impossible to have one reaction without the other
• tends to be two -ve electrons, two +ve protons or 2 hydrogen atoms

Question 19

what happens when making/breaking C-C bonds?

Answer 19

breaking bonds releases energy, making bonds uses energy

internal arrangements also occur i.e nothing added or taken away however molecules have been moved about

Question 20

what happens in a group transfer?

Answer 20

the functional group is transferred i.e in glycolysis the phosphate group is transferred (ATP–> ADP)

Question 21

what are condensation/hydrolysis reactions?

Answer 21

condensation reactions - molecules joined together by removing H2O
hydrolysis reactions
- bonds broken by adding H2O

Question 22

what is a protein?

Answer 22

polymers of amino acids linked by peptide bonds

Question 23

what is a nucleic acid?

Answer 23

polymers of nucleotide monomers linked by 3’,5’-phosphodiester bonds
nucleotides composed of a phosphate, a pentose sugar and a base (purine/pyramidine)
RNA contains uracil instead of thymine

Question 24

what are polysaccharides?

Answer 24

polymers of sugar monomers linked by glycosidic bonds (glucose is the main energy source - polysaccharide)

Question 25

how are glucose polymers formed?

Answer 25

glucose monomers are formed by condensation reactions

One glucose monomer is linked to another which locks it in the cyclic form

Question 26

what is a lipid?

Answer 26

usually contain one or more long chain fatty acids

• FAs are an energy source
• if there is a double bond in FA chain = unsaturated, contains kink in the chain

Question 27

what are the 2 laws that govern energy changes?

Answer 27

1. energy can be converted from one form to another but the total energy remains constant
2. all energy changes result in more disorder (increase entropy)

Question 28

what is Gibbs Free Energy?

Answer 28

a calculation that determines the amount of useful free energy
Enthalpy - H, heat is released to surroundings
Entropy - S, randomness/disorder
Absolute temperature - T
G = H - TS

Question 29

free energy change

Answer 29

a spontaneous process must decrease enthalpy (H) and or increase entropy (S). Spontaneous energy changes will have a negative value for their change in free energy
deltaG = deltaH - TdeltaS

Question 30

what does reaction coupling mean?

Answer 30

used to carry out thermodynamically unfavourable reactions

- spontaneous reactions that give off energy will be coupled with reactions that require energy

Question 31

what is metabolism?

Answer 31

the chemical processes in a living organism in which food is broken down and used for energy production and tissue growth

Question 32

what is the difference between catabolic and anabolic?

Answer 32

catabolic processes - when food is broken down into useful forms of energy
anabolic pathways - energy is used in biosynthesis

Question 33

what are intermediary metabolites?

Answer 33

compounds which capture the energy given off - ADP/NADP+

Question 34

what happens in ATP hydrolysis?

Answer 34

ATP –> ADP releases free energy. It is harnessed to drive thermodynamically unfavourable reactions

• Exergonic (catabolic pathway) - saves free energy by forming ATP
• Endergonic (anabolic pathway) - is supplied with free energy through conversion of ATP to ADP

Question 35

PEP –> pyruvate reaction

Answer 35

PEP is an intermediary for a reaction that goes on to produce ATP - stores potential energy

Question 36

how is hydrogen bonding and solubility related?

Answer 36

molecules that form H bonds are water soluble (hydrophilic)

i.e sugars, alcohol, ketones, compounds with N-H bonds

Question 37

what happens when hydrophilic molecules dissolve in water?

Answer 37

when they dissolve, the water-water H bonding and solute-solute H bonding is replaced with more energetically favourable solute-water H bonding

Question 38

what happens when ions dissolve in water?

Answer 38

regardless of whether it is - or +vely charged, it will be surrounded by H+ or O-. The water forms screens around each ion to keep it in solution

Question 39

what happens to uncharged molecules in water?

Answer 39

non-polar (uncharged) molecules arrange themselves in a manner so to minimise disruption of H-bonding among surrounding water molecules = hydrophobic effect

Question 40

what happens to lipids in water?

Answer 40

lipids will stick together (more energetically favourable). Only lipid portions at the edge of the cluster forces disorder of water

Question 41

what is an amphipathic molecule and what happens in water?

Answer 41

amphipathic molecules contain both hydrophilic/phobic parts - phospholipids.
In water phospholipids minimise the disruption of water H-bonds by forming micelles/bilayers with the hydrophobic FA tails shielded from the water

Question 42

how are hydrophobic lipids transported?

Answer 42

lipids are transported in the blood in a chylomicron - the phospholipid heads and outer edges of the proteins are hydrophilic which allow the fat to be transported

Question 43

can water dissociate?

Answer 43

yes, water can dissociate - slightly charged.
H2O H+ + OH-
The equilibrium of water is described as
Keq = [H+][OH-]/[H2O].
However the conc of water is high in pure water so can be removed from the equation to give
Kw = [H+][OH-]

Question 44

how is water pH=7?

Answer 44

in pure water -log[H+]= -log[OH-] = 7, then the negative values are taken away this is pH=pOH = 7

Question 45

what are strong/weak substances?

Answer 45

strong acids/bases are substances that fully dissociate in water (bad biologically as they can protonate other molecules - alters function)
weak acids/bases can only dissociate (influence systems via buffering capability)

Question 46

what are buffers?

Answer 46

buffers are solutions of weak acids (proton donors). Acid loses the proton donating it to form the conjugate acid-base pair (it is a reversible reaction)

Question 47

what is the equilibrium constant/acid dissociation constant?

Answer 47

Keq/Ka = [H+][A-]/[HA]

Question 48

examples of buffers

Answer 48

acetic acid, ammonium ion, carbonic acid, bicarbonate, phosphoric acid

Question 49

how do buffers work?

Answer 49

there are two equilibriums in play in a weak acid
H2O H+ + OH- but also
HA H+ + A- (reactions are linked because of H+)
- when a strong base is added, the OH- combines with free H+ to form H2O. As H+ are removed to form H2O, the weak acid dissociates to maintain equilibrium and more Ac- left.

Question 50

what is the Henderson-Hasselbalch equation?

Answer 50

way of relating the acid dissociation equation to the buffering ability of a weak acid/conjugate base
pH = pKa + log([A-]/[HA]0

Question 51

examples of buffers…blood bicarbonate

Answer 51

If blood did not have the bicarbonate buffer system then the pH would fluctuate wildly as cellular products of acids would cause marked drops in blood pH. It is important to maintain a blood pH of around 7.4, so patients with high acid levels (metabolic acidosis) will often have blood pH, [HCO3-] and [CO2] monitored.