Biological molecules p57-65 Flashcards
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What are all proteins made up of?
(not amino acids in this case)
one or more polypeptide chains
Give two examples of proteins in the blood.
- some hormones such as insulin and glucagon
- oxygen-carrying pigment such as haemoglobin and myoglobin
Which proteins are for muscle contraction?
actin and myosin
What are examples of storage products made of protein?
ovalbumin in egg
casein in milk
Name 5 examples of proteins.
enzymes, transport proteins, antibodies, collagen (bones, artery wall), keratin (hair, nails and surface layer of skin)
What do amino acids consist of?
amino group -NH2
carboxylic acid group -COOH
carbon and hydrogen atom
R group (eg: hydrogen atom)
Different amino acids have different…
R groups
Two amino acids linked together is
a dipeptide
Many amino acids linked together is
a polypeptide
Explain the peptide bond between two amino acids.
The -HO of the carboxylic acid group of one amino acid. The H of the amino group of the second amino acid.
C of first bonds with N of second.
Where is protein digested?
stomach and the small intestine
Primary structure
which amino acids in which specific sequence
How does the change in a single amino acid (even if there are thousands), affect a protein/polypeptide?
properties changed
Secondary structure
structure of a protein resulting from coiling/folding
What enables non-adjacent amino acids to affect each other?
Polypeptide chain bends back on itself
How are alpha helixes held together?
(bonds)
Held together by hydrogen bonds due to polar characteristics of groups.
Explain hydrogen bonding for an alpha helix.
O of C=O of one.
H of -NH of toher, 4 places ahead
How is a beta pleated sheet held together
hydrogen bonding
Describe the shape of a beta pleated sheet.
looser, straighter shape
What are the hydrogen bonds holding the alpha-helixes and beta-pleated sheets together, easily broken by?
high temperature
pH changes
What does the arrangement of proteins depend on?
The R groups present.
Attractions between amino acids.
Tertiary structure
a folded/coiled secondary structure
Name the four bonds which keep folded proteins in their precise shapes.
Hydrogen bond
Hydrophobic interactions
Ionic bond
Disulfide bond
Hydrogen bond
Hydrogen bonds form between a variety of R groups. Happens between strongly polar groups.
Ionic bond
Ionic bonds form between R groups containing ionised amino and ionised carboxyl groups. Broken down by pH changes.
Disulfide bond
The sulfur atoms of two neighbouring cysteine molecules join with a covalent bond. Broken down by reducing agents.
Hydrophobic interactions
Hydrophobic interactions happen between non-polar R groups. Shape of many proteins are affected by this. Weak, but strong together.
Describe the behavior of hydrophobic and hydrophilic R groups in a watery environment.
Phobics come together, excluding water. They are at the centre, facing away from watery environment.
Philics surround phobics, facing outwards in contact with the watery environment.
Quaternary structure
overall structure formed by polypeptide chains
How many polypeptide chains does haemoglobin have?
4 chains
Which type of stucture is haemoglobin?
quaternary
How are quaternary structure held together?
By the same 4 bonds as in tertiary structures
Give 3 examples of globular proteins.
haemoglobin, myoglobin, enzymes
Describe the shape of globular proteins.
Protein whose molecules curl up into a ball
Why do globular proteins usually curl up?
The phobic can point to molecule’s centre. Philic remain on the outside of molecule.
Are globular proteins usually soluble or insoluble and why?
Soluble, because water molecules cluster around philic.
Many globular proteins have a role in..
metabolic reactions
Why do globular proteins have precise shapes?
For their functions.
Are fibrous proteins usually soluble or insoluble?
not usually soluble
What is the role of fibrous proteins?
Most have structural roles. Eg: keratin makes structure waterproof.
Give two examples of fibrous proteins.
keratin and collagen
Fibrous proteins form..
long strands
What is each chain of a haemoglobin molecule?
A protein called globin, which is related to myoglobin, and so, has a similar tertiary structure.
How many types of globin are there?
many
Which globins are used to make haemoglobin?
alpha-globin and beta-globin
What are the haemoglobin chains made of?
Two alpha chains made of alpha-globin, two beta chains made of beta-globin
Describe the shape of a haemoglobin molecule.
nearly spherical
What is important in holding the correct 3D shape of haemoglobin?
interactions between the phobic
What happens in sickle cell anemia?
one amino acid on beta-chain surface is replaced with another
glutamic acid (polar) is replaced with valine (non-polar)
What is the consequence of sickle cell anemia?
Haemoglobin molecule is less soluble
What does each haemoglobin chain have?
haem group
What is a haem group?
An important, permanent part of a protein molecule (not out of amino acids) is called a prosthetic group.
What is the haem group responsible for?
Colour which depends on whether the iron atoms are combined with oxygen. Oxyhaemoglobin is bright red. Without O, darkish, blueish red.
What does a haem group contain?
an iron atom to which an oxygen molecule can bind
Is collagen globular or fibrous?
Soluble or insoluble?
insoluble and fibrous
Role of collagen
structural role
Describe collagen
flexible, high tensile strength
Describe collagen’s structure.
Each chain is in the shape of a helix. Three chains. They wind around each other to form a triple helix. Held together by H and some covalent bonds.
What is the most common protein?
collagen, making up 25% of protein in mammals
Almost every third amino acid in each polypeptide of collagen is..
glycine, the smallest amino acid
Where is glycine found in collagen?
Found on the inside of strands. Its small size allows the three strands to lie close together and form a tight coil.
Parallel collagen molecules are cross-linked forming..
fibrils
Many fibrils alongside each other, forms..
fibres
How are parallel collagen molecules cross-linked?
Covalent bonds between Rgroups of amino acids lying next to each other.
Many collagen molecules make up..
one collagen fibre
How do the ends of the parallel collagen molecules look?
Staggard, to strengthen the structure
