TBL 1 Cells and Organelles Flashcards
Eukaryotic cell size is limited by a minimum and maximum.
The lower limit is __________; whereas the upper limit is __________.
Lower limit: Least cell volume required to fit all organelles
Upper limit: Maximum volume such that the surface area-to-volume ratio for exchange of substances is not compromised.
The cell ________ (organelle) is responsible for the control of cellular organisation and all cellular activities.
nucleus
The nucleus is embedded with specialised pore complexes, _________, allowing for the movement of resources to and from the nucleus.
Nuclear pores
The nucleus has a DOUBLE membrane (__________) that becomes continuous with the __________(organelle), allowing for continuous passage of mRNA to ribosomes embedded in the membrane of the ER.
nuclear envelope; rough ER
Endosymbiotic theory: _________ and ________ (organelles in eukaryotes) are believed to be derived from the incorporation of prokaryotic cells.
Both of them have their own _______ DNA.
mitochondria and chloroplast; circular DNA
Conventional light microscopes allow us to see up to ___ (units); whereas electron microscope allows us to see up to ___.
Light - micrometres
Electron - nanometres
________ motion is the spontaneous movement of molecules into and out of the cells, and is what allows molecules to diffuse freely.
Brownian motion
__________ converts angiotensin I to bioactive angiotensin II which helps to (increase/decrease) blood pressure.
Angiotensin Converting Enzyme (ACE)
___________ is responsible for the removal of phosphate from glucose-6-phosphate to increase the bioavailability of glucose. It cleaves phosphate to allow the release of glucose into the bloodstream when the blood glucose level is low.
Glucose-6-phosphatase
__________ (Clinical condition) is an autosomal recessive disorder resulting from G6PD deficiency. (low levels of glucose-6-phosphatase enzyme –> hypoglycaemia)
Von Glerke’s disease
Enzymes act by _________ that impede chemical reactions from happening.
lowering activation energy
The first law of thermodynamics states that
Energy can neither be created nor destroyed. (only converted)
The second law of thermodynamics states that
Any isolated system tends towards entropy/disorderliness. (i.e. degree of disorder can only increase)
Biological systems are very well-ordered - they follow the second law of thermodynamics by taking energy from the _________ surrounding the cell and investing it in chemical reactions which maintain order.
take energy from surrounding environment
=> increased disorder as a whole system
________ is the amount of energy within the molecule that can perform useful work at a constant temperature.
Gibbs free energy
delta(G) =
free energy of products - free energy of reactants
Change in Gibbs free energy is a measure of the change in order within the cell and change in entropy of the system.
-
Reactions are spontaneous if delta(G) <0 (exergonic) or >0 (endogenic)?
delta(G) < 0
i.e. free energy of reactants > free energy of products
Do enzymes change the delta(G) of the reaction?
No. Spontaneous reactions (i.e. delta(G) <0) might not proceed due to slow kinetics, so enzymes are used to speed up the rate without changing delta(G) of the reaction.
Anabolic reactions are generally energetically unfavourable (i.e. delta(G) <0), so how do cells overcome this problem?
Couple anabolic reactions to energetically favourable reactions like ATP hydrolysis –> delta(G overall) > 0 and is therefore spontaneous.
In ATP hydrolysis, energy is released through the hydrolysis of __________ bonds.
Phosphoanhydride bonds
__________ is the minimum amount of energy that reactants need to possess before the reaction can proceed.
Activation energy
Catalytic amino acid residues within the enzyme participate in the creation/breaking of bonds of substrates by ______________.
altering electron arrangement (redox reactions)
Stressing bonds i.e. ________ of substrate molecules into a certain shape causes them to resemble the _________, which is a particular conformation where atoms are rearranged geometrically and electrically so they are more susceptible to reaction.
Contortion; transition state
The _________ hypothesis states that the 3D conformation of the substrate is completely and exactly complementary to that of the enzymatic active site.
lock-and-key
=> only bind to one substrate and catalyse one reaction (Substrate specificity)
The ________ hypothesis suggests that the 3D conformation of the substrate is not completely complementary to that of the enzymatic active site.
induced fit
=> accounts for the ability of enzymes to bind to substrates which are structurally/chemically similar
(group specificity)
_______ is a component of tears and nasal secretions and serves as a first line of defence against bacterial infections.
Lysozyme
Lysozyme functions to catalyse ________.
catalyse the hydrolysis of sugar molecules within the bacterial cell walls (cells are induced to undergo lysis and die).
Substrate of lysozyme:
Alternating polysaccharide co-polymers of N-acetyl glucosamine (NAG) and N-acetyl muramic acid (NAM) - unit structure of bacterial cell walls.
Lysozyme cleaves at the __________ connecting C_ of NAM to C_ of NAG.
cleaves at the B(1,4) glycosidic linkage connecting C1 of NAM to C4 of NAG
Lysozyme (protein enzyme) secondary structure:
both alpha helical and B pleated sheets
Lysozyme (acidic/basic) catalytic amino acid residues:
Glutamate-35 and Aspartic acid-52
Structure and function of lysozyme:
_____ (AA) protonates oxygen in the glycosidic bond, breaking the bond holding the sugar molecules together.
Water molecule enters and is deprotonated by _____.
_____ (AA) stabilises the positive charge in the transition state, while the OH- ion attacks the ____ carbocation to add a -OH group.
Glu-35 protonates oxygen, breaking bond.
Glu-35 accepts H+ from H2O, forming OH-.
Asp-52 stabilises positive charge, while -OH ion attacks the NAM carbocation to add a OH group.
