BIO MOLECULES Pt 3 (Proteins)

• Carbon, hydrogen, oxygen & nitrogen. (some proteins also contain sulfur)
• 50% of organic matter in cells (proteins)

• Structural components - eg. muscle and bone
• Membrane carriers and pores (provide transport across membranes) - eg. for active transport and facilitated diffusion.
• All enzymes are proteins
• Many hormones
• Antibodies
• (Overall, proteins provide building material important for growth and repair in all organisms. Also crucial to most metabolic activity)

• All have amino group at one end of the molecule
• An acid group at the other end of molecule
• And a carbon in between.

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• Amino acids are joined end-to-end to give a repeating "backbone".
• NCCNCCNCC...

• In glycine it is a hydrogen atom (simplest amino acid)
• Some R groups are large - larger than CNN part of molecue.
• Some are positively charged, others negatively, some are hydrophobic, some are hydrophilic.

Around 8-10 types of the amino acids that cannot build from material they take into their bodies, and thus are essential part of the diet. (Most of these are found in meat)

• Cannot store
• Process called deamination
• Takes place in the liver - amino groups converted into urea and removed in urine.
• Because the amino groups makes them toxic if too much is present.

• Peptide bond
• New molecule called dipeptide
• The condensation reactions happen between the acid group of one amino acid and the amino group of another.

Because part of the molecule is lost during condensation reaction that produces the peptide bond.

• single
• more than one

• On ribosomes
• Called protein synthesis
• Uses information in the form of a molecule called messenger RNA

• Function of protein determined by its structure.
• The unique sequence of amino acids of a polypeptide or protein is called its primary structure.

Protease enzymes

Hormone regulation - target cells for a specific hormone will have enzymes that can break down that hormone, so that its effects are not permanent.

Always state that condensation or hydrolysis reactions are enzyme-catalysed reactions if you are referring to the process within organisms.

• Coiled up or pleated
• These coils and pleats are held in place by numerous hydrogen bonds.
• Amount depends upon amino acids, so depends on the primary structure.

• Formed when chain of amino acids coils or folds to form an alpha helix or a beta pleated sheet.
• Hydrogen bonds hold the coils in place.

Refers to the overall 3D structure of the final polypeptide or protein molecule.

• Hormones need to be a specific shape to fit into the hormone receptor.
• Enzymes need to have an active site which is complementary in shape to that of its substrate.
• Structural proteins such as collagen is shaped to be strong by protein chains being wound around each other in specific way.

• Disulfide bonds: (eg 2 cysteine amino acids)
• Ionic bonds: some R groups carry a charge and therefore opposite charged groups
• Hydrogen bonds: slightly negative and positive (like in secondary structure).
• Hydrophobic and hydrophilic interactions

• The increased kinetic energy causes the molecules to vibrate and breaks some of the bonds holding tertiary structure in place.
• The protein denatures.

• Globular proteins - roll up into ball-shaped structure. Any hydrophobic R-groups turned inwards towards centre, and any hydrophilic R-groups are outside. (makes it insoluble). Usually have metabolic roles. eg. enzymes
• Fibrous proteins - form fibres. Most have regular, repetitive sequences of amino acids. Usually insoluble in water. Usually structural roles. eg. keratin & cartilage

• Made up of more than one polypeptide subunit joined together, or a polypeptide and an inorganic component. They will only function if all the subunits are present.
• eg. haemoglobin & collagen (need to know about them) and insulin.

• Groups in a protein that are not made of amino acids but are still essential part of the molecule.
• eg. haem group of haemoglobin (need to know)

The specialised part of each polypeptide in a haemoglobin molecule which contains an iron (Fe^2) ion. The oxygen molecule binds to the iron ion in the haem group, and this is responsible for the red colour of blood.

• Globular protein
• Soluble in water (hydrophilic region on outside)
• Wide range of amino acids in primary structure (give specific interactions to form tertiary structure which is vital)
• Contains prosthetic group - haem group
• Much of molecule is wound into alpha helix structures

• Three polypeptide chains wound around each other.
• Hydrogen bonds between chains

Collagen molecules forming covalent bonds called cross-links staggered along molecule.

• Walls of arteries (prevents high pressure from bursting the walls)
• Tendons
• Bones - reinforced with materials such as calcium phosphate
• Cosmetic treatments

• Fibrous protein
• Insoluble in water
• Approx 35% of primary structure is one type of amino acid (glycine)
• Does not have a prosthetic group
• Much of molecule consists of left-handed helix structures.