General Biochemistry Flashcards
What are prokaryotic cells
They comprise bacteria, they are relatively simple and have no true nucleus and no internal membrane bound organelles
What are eukaryotic cells
Found in higher animals and plants
Large complex molecules
What is the function of the plasma membrane
Semi permeable barrier between cytoplasm and external enviroment
What is the function of the nucleus
Controls cell activity
DNA found here
What is the role of the nucleolus
Ribosomes constructed here
Where is the site of transcription
The nucleus
What is the role of ribosomes
Main role id to facilitate protein translation
What is the rough endoplasmic reticulum
Contains ribosomes
Protein modification and production
What is the smooth endoplasmic reticulum
Predominant function is manufacturing of lipids
No ribosomes
What role does the smooth ER play in the liver
Converts organic chemicals into safer water soluble products
In the liver can double the surface area
Function of the golgi aparatus
- further modifies proteins
- stores proteins
- packages proteins
Function of vacuoles
Used as storage areas
Function of vesicles
Function in transport
Function of lysosomes
The breakdown of extracellular materials, large vesicles formed by the Golgi apparatus
Function of mitochondria
Powerhouse of the cell
ATP formation
What are the two membranes of the mitochondria
- outer membrane - smooth and sieve like
- inner membrane folded into CRISTAE - surfaces on which ATP is generated
Function of the cytoplasm
Facilitates transport of material around the cell
What is the cytoskeleton
In eukaryotic cells there are fibrous proteins in the cytoplasm known as the cytoskeleton
- maintain shape of cell
- anchors organelles
What is a buffer
A solution which resists change in pH when acid or alkali is added to it
What is the major buffer in saliva
Bicarbonate
How do you calculate the pH from the hydrogen ion concentration of a solution
pH = -log10(H+)
What is the pH of a solution with (H+) of 0.00001M
PH 5
What are acids
A substance which in water tends to produce H+ ions
What is a base
A substance which in water tends to combine with H+ ions
What is the relationship between the strength of acid and Ka value
The stronger the acid the higher the Ka and the lower the pKa
What is Ka
The acid dissociation constant
What is pKa
A number that describes the acidity of a particular molecule
What is the Henderson-Hasselbalch Equation
pH = pKa+log10(B-)/(A)
How do you calculate pKa
pKa=-log10Ka
What are buffer solutions made of
Consist of a conjugate acid base pair of either a weak acid or weak base
What is the role of buffering in the body
Maintains body pH homeostasis
Why is buffering in the mouth important
Limits pH changes due to acid production by plaque bacteria
When is buffering most effective
When concentration of acid = concentration of conjugate base
When do buffers operate optimally
When half dissociated
Important buffers in saliva
Histatins
Bicarbonate
Phosphate
What acids are produced by oral bacteria
- lactic acid
- formic acid
- acetic acid
- propionic acid
- butyric acid
What is tooth erosion caused by
A direct result of acid in the diet on the teeth
What are the 3 different pKa values that bicarbonate acts as a buffer
PKa = 2.16, 7.21, 12.32
What are chelating agents
Chemical compounds that bound tightly to metal ions
Could have an erosive effect on teeth
Fruit juices contain chelating agents
What are some biological roles of proteins
- transport
- storage
- catalysts
- motion
What is electronegativity
The power of an atom to attract electrons towards itself
Where are L isomers found
Proteins
Where are D isomers found
Bacterial cell walls
What is a primary structure of a protein
Amino acid sequence
What is secondary structure of a protein
Regions of amino acid chains that are stabilised by hydrogen bonds between chains
What is tertiary structure of a protein
3D arrangement of all atoms in polypeptide chains
What is quaternary structure of a protein
3D interaction of protein subunits in proteins with more than one polypeptide
What is an alpha helix
Secondary structure of protein
Rod like
Found in strong extensible proteins
Describe B pleated sheet
Zigzag chains
Found in proteins where flexibility is needed
What protein has the triple helix structure
Collagen only
Major component of connective tissue
What are fibrous proteins
Insoluble, metabolically unreactive
Collagen, keratin, fibrin ect
What are globular proteins
Spherical
Water soluble
Myoglobin and actin are examples
What is the role of myoglobin
Oxygen storage in muscle
What is haemoglobbin composed of
2 alpha and 2 beta chains
Name some examples of messenger proteins
Insulin
Glucagon
Human growth hormone
Just hormones in general
What are the monomers of polysaccharides
Monosaccharides
What are the functions of polysaccharides
Storage and structure
Glycogen starch for example
What are the monomers of lipids
Fatty acids
What reactions of monosaccharides form disaccharides
Dehydration and hydrolysis
What are sterols
Lipids with some essential biological activity
What does caries involve
Acids that are produced by plaque bacteria
How does fluoride act to reduce tooth solubility
1) reduces enamel solubility at low pH
2) inhibits bacterial metabolism of carbohydrates
3) promotes enamel remineralisation by saliva
What inhibits solubilisation of enamel
An increase in calcium or phosphate concentration will shift the equilibrium to the left this inhibits solubilisation and inhibit remineralisation
What is a null hypothesis
States there is no significant difference between two variables in a hypothesis
What are enzymes
Enzymes are biological catalysts
How do enzymes act
Accelerate the time it takes to reach equilibrium
What is the role of amylase
Found in saliva, converts starch into sugars
What is the role of maltose
Breaks the sugar maltose into glucose
How do enzymes work
Lock and key model
Induced fit model
What are enzymes usually
Proteins
What is the standard free energy change
The difference between energies of reactants and products
What does reaction rate depend on
Reaction rate depends on the activation energy
What is the activation energy
The energy input required to initiate a reaction
What is the effect of an enzyme on activation energy
Lowers activation energy
What factors can affect the rate of an enzyme reaction
- temperature
- pH
- enzyme/substrate concentration
- inhibitors and activators
- covalent modification
What is V max
Maximum reaction rate
What is Km
The substrate concentration at which half of the maximum velocity is achieved
What is an irreversible inhibitor
Damages enzymes beyond repair
Generally cause covalent modifications of the enzyme
What is a reversible inhibitor
Full enzyme activity is regained when the inhibitor is removed
What is feedback inhibition
Control of metabolic pathways often occurs by feedback inhibition this is often done by the product of the pathway acting as an inhibitor on an earlier step in the pathway
What is the different between a competitive and non competitive inhibitor
Competitive - substrate and inhibitor compete for the same binding site
Non competitive - bind to an allosteric site on the enzyme
What are allosteric enzymes
Possesses multiple subunits
Contains a region in which small effector molecules can bind
Positive modulators - increase affinity for active site
Negative modulators - decrease affinity for activity site