3.1.4 Proteins 3.1.4.1 General Properties Of Proteins Flashcards
3 examples of proteins that are vital compounds of all living organisms
Enzymes
Antibodies
Hormones
3 functions of proteins in the body e.g
Holding body together
Controlling body chemistry (metabolism)
Fighting off disease (immune response)
What element do organic molecules contain
Carbon
What type of molecules are proteins
What 4 elements do they always contain
Large, complex molecules
Carbon, hydrogen, oxygen, nitrogen
What’s nitrogen in proteins for
Growth
What do mostly primary + secondary proteins sometimes contain
Sulphur
What are the monomers that make up proteins
Amino acids
What do amino acids mostly all end in
E.g
‘-ine’
Proline, valine
2 words that link with nitrogen
Amino
Amine
Amide
2 parts of an amino acid that always stay the same
Amino group
Acid group
What’s the formula of the amino group
NH2
What’s the formula of the acid group
COOH
What part of an amino acid is always different
The R group
How many different amino acids are there and so different r groups
E.g
20
E.g glycine, alanine
Where is sulphur found if it’s present in an amino acid
The R group
What’s the test for proteins
The Biuret Test
What do you not need for the test for proteins
Heat
What’s the method for the biuret test
Dissolve test substance in water (crush it if it’s a seed or really solid food)
Add biuret reagent
What’s the biuret reagent consist of
Copper sulfate + sodium hydroxide mixture
What shows protein is present at the end of the biuret test
Change in colour from blue to lilac/purple
What dl enzymes do in the body
The controlling
How are enzymes made
E.g
By adding ‘-ase’ to the substrate
E.g
Lactase breaks down lactose
2 types of enzymes
Intracellular (working inside cells) Extra cellular (working outside cells) - fungi
How do amino acids join
What bonds are formed between them
Whats released
By condensation reactions
Releasing water
Forming peptide bonds
How many amino acids In a dipeptide
2
How many amino acids In a tripeptide
3
How many amino acids In a polypeptide
Many
Whats protein made from (not amino acids)
E.g
1/more polypeptides (polymers)
E.g haemoglobin molecule made from 4 polypeptides (2 alpha + 2 beta polypeptide chains)
What has the backbone N-C-C-N-C-C
Dipeptide
How many levels of structure do proteins have
4
What’s the first structure called
What is it
Primary structure
The sequence of amino acids (order in which they are joined)
3 words describing the primary structure
Long, fibrous strands
What type of proteins are primary and secondary structure
Structural
What’s the 2nd level of proteins structure
What’s the amino acid chain like now
Secondary structure
Folded and coiled
What’s the secondary structure held in place by
Hydrogen bonds
2 most common secondary structure proteins
Alpha helix-spiral shape
Beta sheet - pleated like folded paper e.g silk from worms
What’s the 3rd level of protein structure called
What’s it like
Tertiary structure
Overall shape of amino acid chain (globular) e.g whole polypeptide
How does the tertiary structure become globular
When in water e.g cytoplasm , a wide variety of forces combine to twist, fold and bend the polypeptide into its most stable shape
What are there many areas of in the tertiary structure
Secondary structure
What type of proteins are the 3rd and 4th structural level
Functional
What’s the 4th structural protein level called
When does it occur
E.g
Quaternary structure
When the protein has more than 1 polypeptide chain
E.g haemoglobin has 4
What structure does a protein made up of just 1 polypeptide chain not have
Quaternary
What component do quaternary proteins often have
E.g
A non-protein component which is sometimes an ion
E.g the haem in haemoglobin
What group is the haem in haemoglobin know as
Prosthetic group
What are the 2 main groups protein structure can be split into
Globular
Fibrous
What type of protein is globular
Functional - tertiary
What type of protein is fibrous
Structural - secondary
2 facts about globular proteins
Generally rounded in shape
Tend to have a chemical function
4 examples of chemical functions globular proteins may have
What are these all
Enzymes Hormones e.g insulin Haemoglobin Antibodies Membrane proteins
All shape-specific
2 facts about fibrous proteins
Usually long,thin molecules
Generally have a structural function
What are fibrous proteins the fabric of
The body
3 examples of fibrous proteins and their uses
Collagen - strength to tissues
Keratin - strength to skin, hair, nails
Actin + myosin - muscles contract
What 2 relatively weak forces is the shape of globular proteins maintained by
Hydrogen bonds
Ionic bonds
Where do the hydrogen bonds and ionic bonds in globular proteins come from
The acidic and amine groups
What forces to big, tough fibrous proteins rely more on
Strong disulfide bridges
