SfM - Life at the Cellular Level Flashcards
what is a prokaryotic cell?
is an organism with
no nuclear membrane
no mitochondria
no membrane bound structures
what is a eukaryotic cell?
any multicellular organism
nucleus w/ membrane
membrane bound structure
more complex cell membrane
difference between multi- & pluripotent cells?
multipotent - cells can differentiate into many cell types of the one lineage
pluripotent - have the potential to turn into ANY cell type
how does cancer develop?
cells are damaged via wear & tear/DNA damage (radiation etc), body fails to remove damaged cells
how do tumours form?
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
what is apoptosis?
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)
what is the order from cells to systems?
cells –> tissues –> organs –> systems
what are the 4 tissue types?
connective, epithelial, nervous, muscular
what is the plasma membrane’s function?
transport, intercellular joining, enzymatic activity, cell-cell recognition, receptors for signal transduction, attachment to the cytoskeleton and ECM
what are the different types of transport?
passive diffusion facilitated diffusion endocytosis exocytosis (constitutive/regulated)
examples of occluding junctions?
tight junctions (seals gaps between epithelial cells - creates physical barrier to random diffusion)
what are cell-cell anchoring junctions?
links between cells
- adherens junction (connects actin filament bundles in adjacent cells)
- desmosomes (connects keratin intermediate filaments between adjacent cells)
channel forming junctions
gap junction (allows passage of small water-soluble molecules from cell to cell)
cell-matrix anchoring junctions
actin-linked cell-matrix adhesion anchors
(links actin filaments in cell to ECM)
hemidesmosomes
(anchors intermediate filaments in cell to ECM)
what happens when cell adhesion goes wrong?
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
examples & definition of cell signalling
- 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)
list the cellular organelles
mitochondria nucleus endoplasmic reticulum (smooth and rough) golgi apparatus lysosomes cytoskeleton cilia/flagella
what is a REDOX reaction?
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
what happens when making/breaking C-C bonds?
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
what happens in a group transfer?
the functional group is transferred i.e in glycolysis the phosphate group is transferred (ATP–> ADP)
what are condensation/hydrolysis reactions?
condensation reactions - molecules joined together by removing H2O
hydrolysis reactions
- bonds broken by adding H2O
what is a protein?
polymers of amino acids linked by peptide bonds
what is a nucleic acid?
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
what are polysaccharides?
polymers of sugar monomers linked by glycosidic bonds (glucose is the main energy source - polysaccharide)
how are glucose polymers formed?
glucose monomers are formed by condensation reactions
One glucose monomer is linked to another which locks it in the cyclic form
what is a lipid?
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
what are the 2 laws that govern energy changes?
- energy can be converted from one form to another but the total energy remains constant
- all energy changes result in more disorder (increase entropy)
what is Gibbs Free Energy?
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
free energy change
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
what does reaction coupling mean?
used to carry out thermodynamically unfavourable reactions
- spontaneous reactions that give off energy will be coupled with reactions that require energy
what is metabolism?
the chemical processes in a living organism in which food is broken down and used for energy production and tissue growth
what is the difference between catabolic and anabolic?
catabolic processes - when food is broken down into useful forms of energy
anabolic pathways - energy is used in biosynthesis
what are intermediary metabolites?
compounds which capture the energy given off - ADP/NADP+
what happens in ATP hydrolysis?
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
PEP –> pyruvate reaction
PEP is an intermediary for a reaction that goes on to produce ATP - stores potential energy
how is hydrogen bonding and solubility related?
molecules that form H bonds are water soluble (hydrophilic)
i.e sugars, alcohol, ketones, compounds with N-H bonds
what happens when hydrophilic molecules dissolve in water?
when they dissolve, the water-water H bonding and solute-solute H bonding is replaced with more energetically favourable solute-water H bonding
what happens when ions dissolve in water?
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
what happens to uncharged molecules in water?
non-polar (uncharged) molecules arrange themselves in a manner so to minimise disruption of H-bonding among surrounding water molecules = hydrophobic effect
what happens to lipids in water?
lipids will stick together (more energetically favourable). Only lipid portions at the edge of the cluster forces disorder of water
what is an amphipathic molecule and what happens in water?
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
how are hydrophobic lipids transported?
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
can water dissociate?
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-]
how is water pH=7?
in pure water -log[H+]= -log[OH-] = 7, then the negative values are taken away this is pH=pOH = 7
what are strong/weak substances?
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)
what are buffers?
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)
what is the equilibrium constant/acid dissociation constant?
Keq/Ka = [H+][A-]/[HA]
examples of buffers
acetic acid, ammonium ion, carbonic acid, bicarbonate, phosphoric acid
how do buffers work?
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.
what is the Henderson-Hasselbalch equation?
way of relating the acid dissociation equation to the buffering ability of a weak acid/conjugate base
pH = pKa + log([A-]/[HA]0
examples of buffers…blood bicarbonate
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.
