L1 - Amino acids and proteins Flashcards Preview

LS1 MGD > L1 - Amino acids and proteins > Flashcards

Flashcards in L1 - Amino acids and proteins Deck (41):

What is a basal body?

An organelle made up of a centriole and short cylinder configuration of microtubules


Name 5 specialised cell types

Epithelial cells, muscle cells, nerve cells, adipocytes and erythrocytes


What is the most prolific cell in the body?

Epithelial cells


Name three differences between eukaryotes and prokaryotes

1. Bacteria do not have a separate nucleus
2. Bacteria have a cell wall and a plasma membrane
3. Bacteria lack most organelles


What is the difference between the bonds that hold macromolecules/ complexes together and those that hold Monomeric units together?

Macromolecules are held together by non-covalent interactions whereas Monomeric units are held together with covalent bonds


Name four types of non-covalent interactions

1. Hydrogen bonds
2. Ionic interactions
3. Van Der Waals interactions
4. Hydrophobic interactions


Which atoms can form hydrogen bonds?

A hydrogen atom attached to an electronegative atom (O,N or F) which therefore has a partial positive charge and an electronegative atom with a partial negative charge


What makes a molecule soluble or insoluble in water?

Whether the molecule is polar and can form hydrogen bonds with water and dissolve, or whether it is non-polar and cannot form hydrogen bonds and therefore can't dissolve


What is the meaning of Amphipathic?

Molecules that have polar and non-polar regions


Describe some roles of protein in the body

Catalysts - enzymes
Transporters (O2, Fe)
Structural support (e.g. Collagens in skin and bone)
Machines (muscular contraction and motion)
Immune protection (Ig's)
Ion channels (allow charged molecules across PM)
Receptors (for hormones and neurotransmitters)
Ligands in cell signalling (growth factors etc.)


What intrinsic factors of the polypeptide chain determine protein structure?

The chemical and physical properties of the amino acids


What is a zwitterion?

A neutral molecule which has an even number of positive and negative charges


What does an amino acid structure look like in water?

It forms its ionised form:
1. NH3+
2. COO-
But still has an overall neutral charge - it's a Zwitterion


How do you determin whether an amino acid is an L- or D- isomer?

Rearrange the amino acid so that the hydrogen atom is facing directly towards you and the carboxyl group is facing straight up. Read the amino acid like (CO)(R)(N) - if you read it clock-wise it is the L-isomer, if you read it anti-clockwise it's the D-isomer


What is the protein sterechemical isomer found in the body?



What are the three groups that amino acids are classified into by their side-chains?

1. Non-polar amino acids (hydrophobic)
2. Polar, uncharged amino acids (hydrophilic)
3. Polar, charged amino acids (hydrophilic)
Also aliphatic vs aromatic


How many naturally occuring amino acids are there in the body?



Which is the smallest amino acid?



Why is histidine an honorary member of polar, charged amino acids when it is uncharged?

Due to its pKa it is charged at physiological PH


Lysine has a pKa of 10.5, will its side chain be charged or uncharged at physiological PH?

Positively charged


Glutamate has a pKa of 4.3, will its side chain be charged or uncharged at physiological PH?
What about at PH 4.3?

Negatively charged at physiological PH
Neutral at PH 4.3


Draw a peptide bond forming between two amino acids

Remember to draw this occuring at physiological PH, therefore COO- and NH3+


Describe the characteristics of a peptide bond

1. It's planar: C(alpha), C, O, N, H and C(alpha) all lie in the same plane
2. C-N bond has partial double-bond characteristics, therefore will not rotate
Therefore the peptide bond is rigid and planar


What is meant by the isolelectric point (pI) of a protein?

The PH at which there is no overall NET charge


How would describe the pI of basic proteins?

PI>7, so they contain many positively charged amino acids at physiological PH


How would you describe the pI of acidic proteins?



What is a conjugated protein?

A protein that has covalently linked chemical components in addition to amino acids e.g. Lipids, carbohydrates, phosphate groups, metals etc...


What is the function of mitochondria?

ATP synthesis


What is the function of the Golgi complex?

Export of proteins
Detoxification reactions


What is the function of the Endoplasmic reticulum?

Export of proteins
Lipid and steroid synthesis
(Protein synthesis)
Detoxification reactions
Membrane synthesis


What is the function of the nucleus/ nucleolus?

DNA synthesis and repair
RNA synthesis
RNA processing and ribosome assembly (nucleolus)


What is the function of lysosomes?

Cellular digestion


What is the function of the plasma membrane?

Cell morphology and movement
Transport of ions and small molecules


What is the function of the cytoplasm?

Fatty acid synthesis
Metabolism of carbohydrates, amino acids and nucleotides


What is the function of the ribosome

Protein synthesis


At pH 7.4 what is the concentration of H+ ions?

PH= -log10 [H+]
7.4 = -log10 [H+]
-7.4= log10[H+]
10^-7.4= [H+]


Give TWO definitions of pH

1. A measure of the concentraion of H+ in solution
2. PH= -log10[H+]


Why do metabolically active tissues cause a localised fall in blood pH?

Metabolically active tissues make a lot of acidic substances that will lower the pH of the blood close to them. Examples include lactate, H+, CO2.


Using the Hendersson-Hasselbalch equation (PH=pK+log [A-/HA]), what is the pH of a solution of carbon dioxide and bicarbonate of 1.2mM and 24mM?
Considering the bicarbonate buffer system:
HCO3-+H ions H2CO3 H2O and CO2
And knowing that pK of bicarbonate buffer=6.1

PH= 6.1 + log [24/1,2}
PH=6.1 +log [20]
PH= 7.4


Explain how hyperventilation can cause an increase in blood pH

1. Hyperventilation decreases the partial pressure (concentration) of CO2 in the lungs.
2. This concentration of CO2 dissolved in the blood is proportional to the partial pressure of CO2 gas in the lungs and therefore CO2 blood concentraion falls.
3. This means that the equilibrium position of the bicarbonate buffering reaction in the blood moves to favour the reaction of H+ + HCO3- -> CO2 and H2O. This decrease H+ concentraion in the blood and therefore blood pH rises above its normal 7.4 value.


What effect would a pulmonary obstruction have on blood pH?

A pulmonary obstruction cause an increase in [CO2] in the lungs. Therefore [CO2] in the blood increases, shifting the equilibrium towards production of H+ and HCO3-. Therefore [H+] increases causing a decrease in blood pH below 7.4.