Cell Bio Flashcards
All cells have what features?
- All have a polymer chain(s) in the form of DNA
- Posses nucleotides (protein bound to sugar, bound to a nitrogenous base (A,C,T,G))
- DNA replication via complementary base pairs (templated polymerisation)
- Central dogma is DNA→RNA→Protein
- Enclosed by an amphiphilic plasma membrane
Describe prokaryotes
- Exist as single cell or loose community
- Oval shape with a cilia
- Have cell wall, DNA is randomly distributed within the cytoplasm
- Much smaller than eukaryotes, plants are also eukaryotes
- When a protein with one binding site binds with another protein only with one binding site, you end up with a ____
- When a protein with two binding sites, one up top, one on bottom, continuously bind with other proteins to form a chain, a ____ results
- When a protein with two binding sites, one being slightly askew, bonds with similarly shaped proteins a ___ will form
dimer
helix
ring
What are the three types of protein binding interfaces?
- Surface-string
- Helix-helix
- Surface-surface
What factors affect the shape of proteins?
- Things such as polar v.s nonpolar bonds as well as hydrogen bonds
- The configuration of its amino acids For example hydrophobic clustering is when the hydrophobic AAs (polar bonded) gravitate to the centre of the protein whereas the hydrophilic (non-polar bonded) ones surround the exterior
What is hydrolase?
- Proteins that destroy / breakdown things. There are two types:
1. Endonuclease (destroy nucleic acid from the centre, DNA RNA)
2. Exonuclease (destroy nucleic acid from the ends)
What is a protease?
- Protein that breaks down other proteins
- Binds to ligase called substrates. Acts as a catalyst that permits cells to make or break bonds controllably.
Note:
- Increase in the concentration of substrate ➔ increases the rate at which product is formed, eventually reaching a maximum value (maximum rate/Turnover Number)
____ = the concentration at which the reaction is happening at half its maximum speed
- ____ means that even with a low conc of substrate the reaction can happen at ½ its max speed. So the binding between enzyme and substrate is strong and tight.
- ____ takes a lot of substrate to reach Vmax, so the enzyme and substrate probably bind fairly weakly
Km
Low Km
High Km
How do cells regulate enzyme activity?
- Regulating the expression of the gene that codes the enzyme
- Confining enzymes to specific subcellular compartments
- Protein destruction
- Molecule binding
- _____ Enzymes have two or more binding sites
- _____ site: recognizes the substrate
- _____ site: recognizes a regulatory molecule
- In both positive and negative ____ _____, the regulatory molecule has totally different shape than the enzyme’s substrate
Allosteric
Active
Regulatory
feedback regulation
Describe positive enzymatic regulation
When inactive enzymes and substrates float around loosely. Then after, the introduction of regulatory molecule occurs which bind to the enzymes and encourage them to take up the substrate and become active
Describe negative enzymatic regulation
Active enzymes float around with their substrates. Then regulatory molecules are introduced which bind to the enzymes and encourage them to release their substrates and become inactive
Describe enzymatic transition states
- Substrates pass through intermediate state of altered geometry before forming the products of the reaction
- Transition state: the most unstable intermediate state
- The energy required to get to that unstable intermediate state: Activation Energy
- The activation energy is the major determinant of the reaction rate
- Goes from enzyme binds with substrate → ES → EP → Enzyme + product
What are multienzyme complexes?
- The cell can increase reaction rates without raising substrate concentrations by bringing the various enzymes involved in a reaction sequence together to form a large protein assembly
What is the difference between gated and vesicular transport?
Gated:
- transport between the cytosol and nucleus through nuclear pore complex in the nuclear envelope (which act as selective gates)
Viscle:
- membrane-enclosed transport -ferries proteins from one compartment to another
What do transmembrane protein translocators do?
Directly transport proteins across a membrane from cytosol
Describe the process of protein targeting.
A signal sequence is located on the n-terminus or middle of the polypeptide chain and designates a specific destination. So pretty much tells the protein where to go. These sequences are used to get proteins to their destinations (google maps)
Describe the process of transport through the ER
- A protein is made with an ER signal sequence (ERSS)
- One end of a signal recognition particle (SRP) binds to ERSS to guide it towards destination, the other end blocks the elongation factor binding site so that synthesis pauses
- The SRP receptor which is attached to ER, binds to SRP opening a translocator allowing for the SRP to unbind from the elongation factor site and for protein synthesis to resume, feeding into the ER lumen
- The SRP then unbinds from the SRP receptor and is recycled to repeat the process
Mitochondrial proteins are first fully made as mitochondrial ____ ____ in the cytosol then translocated into the mitochondria via a ___ ____ mechanism
precursor proteins
post-translational