Lecture 3 - introduction to proteins Flashcards
Proteins intro
Polymers of amino acids Proteins carry out or catalyse almost all of the processes required to sense and respond to the environment, to make and breakdown molecules, to grow and replicate and to acquire needed energy to fuel all these processes Some proteins (structural proteins) form much of our physical make up such as muscle, ligaments, hair, nails and tendons
Primer on proteins
Proteins are non-branching polymers that form macromolecules about 50-100 Å in size (1 Å = 10^-10 m)
Each protein is composed of a specific sequence of amino acids joined together by chemical bonds called peptide bonds
Each protein has a distinct sequence that is unique to them
There are only 20 different amino acids used to make proteins
Number of amino acids
20 different amino acids
Amstrung
(1 Å = 10^-10 m)
Amino acid sequence held together by
Peptide bonds
Why do we need to know the structure of proteins?
Structure determines function
Different ways of depicting chemical structure
Skeletal (lines)
Ball and stick
Space-filling
Functions of proteins
Structural - collagen (protein in skin and bones)
Regulatory - insulin (peptide hormone)
Contractile - myosin and actin (muscle proteins)
Transport - Haemoglobin carries oxygen
Storage - Egg white, seed proteins
Protective - antibodies (immune proteins)
Catalytic - hydrolytic in lysosomes
Toxic - Botulinum toxin, diphtheria toxin
Cell signalling - hormone
Insulin - after a meal, insulin is generated and binds to the insulin receptor to signal cells to take up glucose in order to decrease blood glucose levels
Digestion (2)
Trypsin - an enzyme that breaks down proteins during digestion. Enzymes that breakdown proteins are called proteases
Amylase - an enzymes that breaks down starch into sugars. It is found in saliva as well as pancreatic juices
HIV protease
Viruses and bacteria make proteins. They use the same amino acid building blocks. HIV make a protease that is essential for HIV replication
Metabolism (2)
Alcohol dehydrogenase - An enzyme that helps to metabolise ethanol. Enzymes catalyse biochemical reactions (it is a dimer but can function as a monomer)
Hexokinase - an enzyme that adds a phosphate to glucose, after glucose is taken up by the cell. Kinases are enzymes that usually add phosphate to molecules
Oxygen transport (metabolism)
Haemoglobin - binds oxygen in the lungs and carries it in the blood to tissues for use in metabolism (4 chains and each one bings oxygen through a heme group)
Metabolism and energetics - membrane proteins
ATP synthase - membrane protein that generates ATP for use in cellular functions (part membrane proteins and part globular therefore it is part hydrophobic and part hydrophilic)
Immune protection
Antibodies - bind to cellular invaders like bacteria and viruses to help protect the body from infection
Replication and maintenance
DNA polymerase - binds to one strand of DNA and adds the complementary strand to it
RNA polymerase - creates a single strand of RNA that is complementary to one of the strands of duplex DNA
Cell as a bag of…
proteins, lipids, and nucleic acids
Name a protein that is involved in DNA replication
DNA polymerase
Name a protein that is involved in RNA replication
RNA polymerase
Name a protein that is involved in oxygen transport
Haemoglobin
Name a protein that is involved in immune protection
Antibodies
Name a protein that is involved in digestion
Amylase
Trypsin
Name a protein that is involved in metabolism
Alcohol dehydrogenase
Hexokinase
Regular components of amino acids
An amino group, a hydrocarbon, a carboxyl group, and a side chain which determines which amino acid it is and the properties it posesses
Enzymes that break down proteins are called
Proteases
Enzymes that add phosphates to molecules are called
Kinases
