What are the 7 functions of proteins?
1: Enzyme catalysis
2: Defence
3: transport
4: support
5: regulation
6: motion
7: storage
What are the components of an amino acid? What is the role of each group?
- Carboxyl group
- Amino group
- R group
The carboxyl and amino groups have the function of binding to each other to create a protein backbone
The R group influences different molecular interactions for different functions
What are the types of amino acids and which intermolecular interactions take place in each type?
- non-polar, hydrophobic exclusion/van der waals
- polar uncharged, H-bonding, cysteine can make a disulfide bridge
- charged, ionic bonds
- aromatic (special character)
What are the levels of protein organization? name and describe them
Primary: the sequence of amino acids present in the protein (Thr-Cys …).
Secondary: the molecular interactions between the back bone (H bonding) to form beta pleated sheets or alpha helices.
Tertiary: R GROUP
Quaternary: interactions between different polypeptides
How are amino acids numbered and why?
the N-terminus is always #1, because it is always added to the C terminus.
What characteristic do phospholipids have that allows them to form membranes? What in the chemical composition of phospholipids explain this characteristic?
They are half hydrophilic, and half hydrophibic due to the difference in polarity in the hydrophobic, non polar tail and the hydrophilic polar head.
What shapes do phospholipids arange themselves in? How do these phospholipids move in these shapes?
Phospholipids form bilayers, they can swing rotate, undergo transversal diffusion, or lateral diffusion
How does saturation of a phospholipid affect membrane fluidity?
If a phospholipid is unsaturated, it contains cis double bonds which cannot move freely, thus introducing a chink into the bilayer, creating more space between the phospholipids, increasing membrane fluidity
How do organisms influence membrane fluidity?
- animals can introduce cholesterol as a supporting molecule to fill the holes in a membrane and make it more rigid
- other organisms without cholesterol use enzymes to introduce double bonds in the membranes to counter effects of cold
What are the components of a membrane, and what are their functions?
- Phospholipid bilayer, provides selectively permeable bilayer, excludes polar molecules like water, etc.
- interior protein network, reinforces membrane shape
- cell surface markers, allows identification of cells and identifying foreign organisms
- transmembrane proteins, many uses, transport, enzymes, cell surface reception, cell identification, cell adhesion, attachement to cytoskeleton,
What are the types of tansmembrane proteins and what is their function?
transporters: carrying/allowing molecules to diffuse that cannot span the membrane
Enzymes: can be anchored to a membrane, catalyse chemical reactions
Cell surface receptors: allows molecules outside to transmit signal inside a cell
Cell surface identitiy markers: allows other cells to identify cells
Cell to cell adhesion molecules: sticks cells together
Attachment to the cytoskeleton
What is a concentration gradient? Which direction do molecules go?
two areas with different concentrations will to even out, thus molecules travel from high to low concecntration
what are the types of transport, through structure does the compound go, and in what direction?
simple diffusion: membrane, same as conc. gradient
facilitated diffusion: channel/carrier protein, same as conc. gradient
active diffusion: carrier protein, OPPOSITE conc. gradient
what terms are used to refer to levels of tonicity?
Equal conc. : isotonic
low conc. : hypotonic
high conc. : hypertonic
what are gated channels and membrane potential, and what are they used for?
gated chanels have the ability to open or close in response to certain stimuli, this allows for better control over how much of the molecule traverses the membrane
membrane potential is when a voltage is applied to a channel. This is to allow ions to pass through better
How are transmembrane proteins bound to the membrane?
they can be bound to lipid anchors that are directly attached to the tail of a phospholipid
or they can use non polar domains to span the membrane and stay there due to positive interactions between the inside of the membrane
What is osmosis?
diffusion of water across a membrane, opposite of the concentration gradient (high water to low water)
how does the tonicity of the environment affect a cell?
isotonic: no effect
hypotonic: the cell swells, less water concentration inside
hypertonic: cell shrivels, more water conc. inside
What are hydrostatic and osmotic pressures?
hydrostatic pressure is the force of the cytoplasm on the membrane and exerted by the membrane onto the cytoplasm, osmotic pressure is the force of water on the membrane and the membrane applying force to stop water from entering the cell
What methods do cells have of regulating osmotic and hydrostatic pressures?
extrusion: physically pump out water
isosmotic regulation: regulate concentrations by displacing
Turgor pressure: stores ions in the vacuole, then it absorbs more water. The cell wall resists the pressure
What is co-transport?
a form of active transport in which more than 1 molecule traverses the membrane against it’s concentraition gradient
What is a redox reaction (in biology)?
It is the transfer of an electron, this electron is bounded to a proton, making it the transfer of a hydrogen atom. The molecule gaining the H is reduced, the other is oxidised.
How do enzymes speed up reactions and stabilize intermediates
- orienting the substrates
- bringing them closer
- stressing particualr bonds
What is induced fit?
When a substrate binds to the active site of an enzyme, the tertiary interactions in the enzyme change, thus the shape of the enzyme changes slightly to grip the substrate
