Proteins Flashcards
Proteins are made from (6)
- Carbon, hydrogen, oxygen, nitrogen and occasionally sulfur
- Polypeptides that make up the protein are synthesised on the ribosome while they are assembled into proteins when released int o the cytoplasm
Functions of proteins (5)
- They are structural components
- They are membrane carriers and pores
- All enzymes are proteins
- Many hormones are proteins
- Antibodies are proteins
Excess amino acids in mammals (3)
- Too many amino acids can be toxic
- The process of removing the amino group is called deamination
- Amino acids are converted to urea and excreted as piss
Amino acids (4)
- All amino acids have the same structure with a carboxyl group at one end an an amino group at the other end
- The R-group determines the amino acid
- R-groups can be negatively or positively charged while others are hydrophobic or hydrophilic
- The monomeric unit for a protein
Condensation reaction
When the amino group of one amino acid bonds with the carboxyl group of another forming a peptide bond while losing a water molecule
Hydrolysis
The splitting of a bond with the use of a water molecule
Essential amino acids
Amino acids that animals cannot build from materials that they take into their body
Dipeptide bond
The bond between two amino acids
Proteins and polypeptides are made on the…
Ribosomes
Primary structure (3)
- The unique amino acid sequence of a protein
- Held by Peptide bonds
- Folds over to form secondary structure
Secondary structure (3)
- The coiling and pleating of parts of the polypeptide molecule
- Forms an alpha helix or a beta pleated sheet
- Held by H-bonds
Tertiary structure (3)
- The globular structure of a protein
- Made from folded over alpha helices and beta pleated sheets
- Held by disulfide bridges, ionic bonds, H-bonds and hydrophobic interactions
The importance of maintaining tertiary structure (3)
- Tertiary structure is vital for the proteins function
- Hormones have to be a specific shape to fit hormone receptors
- Enzymes have specifically shaped active sites for substrates to fit in
Effect of an increase in heat (3)
- As heat increases, the molecule gains KE
- The molecule vibrates and breaks H-bonds breaking the structure
- With the shape of the active site changed, the enzyme cannot function
Effect of an increase in pH (3)
- As the pH deviates from 7 the concentration of H+ ions increase
- Some H-bonds and ionic bonds are broken as the electrostatic attraction is too great
- The shape of the active site is changed as tertiary structure is lost
Hydrophilic R groups
Water soluble as water molecules can cluster around it
Hydrophobic R groups
Are water insoluble as they turn inwards away from the water source
Globular proteins (4)
- Roll up to form a ball
- Usually soluble
- Usually have metabolic roles
- Examples include enzymes, antibodies and plasma proteins
Fibrous proteins (4)
- Form fibres
- Usually insoluble
- Usually have structural roles
- Examples include collagen in cartilage and keratin in hair
Quaternary structure (2)
- Only some proteins have quaternary structure
- Proteins can have quaternary structure if they have a prosthetic group or more than one polypeptide subunit joined together
Haemoglobin (6)
- Consists of two alpha chains, two beta chains and four haem rings
- Carries O2 and CO2
- Haem gives haemoglobin its colour
- Globular
- Has quaternary structure as it has multiple polypeptide sub units and a prosthetic group
- Soluble
Collagen (6)
- Transport protein
- Fibrous protein
- Made up of three polypeptide chains
- Hydrogen bonds between each polypeptide chain gives the protein its strength
- Each collagen makes staggered covalent bonds with other collagen molecules
- Insoluble
Functions of proteins (5)
- Prevents artery walls from bursting
- Provides a strong connection that allows muscles to pull bones for movement
- Bones are made from collagen
- Cartilage an connective tissues are made from collagen
- Collagen can be injected to revive skin conditions
Haemoglobin (6)
- Consists of two alpha chains, two beta chains and four haem rings
- Carries O2 and CO2
- Haem gives haemoglobin its colour
- Globular
- Has quaternary structure as it has multiple polypeptide sub units and a prosthetic group
- Soluble
Collagen (6)
- Transport protein
- Fibrous protein
- Made up of three polypeptide chains
- Hydrogen bonds between each polypeptide chain gives the protein its strength
- Each collagen makes staggered covalent bonds with other collagen molecules
- Insoluble
Functions of proteins (5)
- Prevents artery walls from bursting
- Provides a strong connection that allows muscles to pull bones for movement
- Bones are made from collagen
- Cartilage an connective tissues are made from collagen
- Collagen can be injected to revive skin conditions
What makes collagen so strong (7)
- Every third amino acid is glycine in the polypeptide chain
- Glycine is a small molecule so they can be tightly bound
- The chains are held together by H-bonds
- Each collagen molecule forms covalent bonds called cross links with neighbouring molecules
- The cross links are staggered along the collagen molecule to prevent lines of weakness
- Their result is a structure called a fibril
- Many fibrils together fomr a fibre
The Biuret Test (5)
- The Biuret test is the test if a sample contains proteins
- Add sodium or potassium hydroxide to the sample
- Add copper sulfate and leave for 5 minutes
- Polypeptides present -> purple
- Polypeptide not present -> blue
Antibodies (4)
- Globular
- Identifies and neutralises pathogens
- Binds onto the antigens of pathogen by the lock and key hypothesis
- Tags pathogens so they can be englufed by phagocytes
Actin and Myosin (3)
- Fibrous
- Myosin converts chemical enrgy into mechanical energy in the form of ATP
- Actin form thin filaments that transmit force generated by myosin to the end of the muscle
Insulin (2)
- Blobular
- Regulates carbohydrate and fat metabolism by causing cells to absorb more glucose from the blood and converts it to glucagon
Monomer
A single molecule that can combine to make a long chain of monomers called a polymer
Which enzymes digest proteins?
Trypsin
Chyrotrypsin
Effect of heat on proteins
- Molecules gain KE as heat increases
- Molecules vibrate more vigorously causing ionic and hydrogen bonds to break
- Protein loses secondary and tertiary structure so is therefore denatured
