proteins

what is a protein a polymer of

amino acids

how many amino acids are there

20

what elements are proteins made up of

carbon, hydrogen, oxygen, nitrogen, varying amounts of sulphur

what is a property of an amino acid

amphoteric (acts as a base or acid)

what part of the amino acid characterises it

R group

how are peptide bonds formed

a condensation reaction between the amino and carboxyl sections of amino acids, resulting in water forming

what are the 4 structures in a protein

primary

secondary

tertiary

quaternary

primary structure

linear sequence of amino acids with peptide bonds

secondary structure

results from hydrogen bond interactions between amino acids

two possible secondary structure formations

alpha helice

beta pleated sheets

tertiary structures

complex folding and twisting to produce a rigid shape (conformation of 3D shape)

what bonds are in a tertiary structure

disulphide bonds

ionic attractions

hydrophobic and hydrophillic interactions

quaternary structure

results from interactions between two or more polypeptide chains

how are the 4 structures reliant on eachother

the sequence defines what secondary structures will be formed which then determines how the protein will fold and whether it will be able to bond to other tertiary structures to form a quaternary structure

classification of proteins (4)

structure

fibrous

globular

composition

function

fibrous

long, narrow, structural proteins that are generally insoluble in water and play key roles in maintaining cell and tissue integrity

globular

compact, roughly spherical, water-soluble proteins that play critical roles in metabolic processes, acting as enzymes, transporters, and antibodies

what is the most important structure level for fibrous

secondary structure

what is the most important structure level for globular

tertiary structure

why is fibrous protein physically strong

due to high proportion of H bonds

what is a property of the fibrous protein

insoluble due to sheer size of molecules

what do fibrous molecules tend to be

structural proteins

what role does the 3d structure play in a globular protein

gives it its function

what is the solubility of a globular protein

soluble

two types of protein

simple

conjugated

simple protein

amino acid only

conjugated protein

contains a non-protein prosthetic group

8 functions of a protein

enzyme

transport

structural

hormones

receptors

defence

motor / contractile

storage

enzyme function

organic catalysts that speed up chemical reactions

eg catalase, amylase, polymerase

transport function

controls exit and entry of substances from a cell

eg chloride channels, glucose channels

structural function

support cell and tissue shape

eg keratin, elastin, collagen

hormone function

chemical messengers used to communicate and induce changes in cells

eg insulin, amylase, adrenaline

receptor function

receive signals from the environment

eg acetylcholine, hormone receptors

defence function

immune system, destroys pathogens

eg antibiotics, complement proteins

motor / contractile function

muscles and moving cell content

eg myosin, actin, kinesin

storage function

reserves for metal ions and other molecules

eg ferretin, casein

5 organelles involved in protein secretory pathway

ribosome

rough endoplasmic reticulum

transport vesicle

golgi apparatus

secretory vesicle

what is exocytosis

an active transport process where cells move large molecules, waste, or secretory products (like hormones and neurotransmitters) out of the cell

what is the ribosomes role

synthesizes proteins

the ribosomes are the sites of protein synthesis. they assemble polypeptide chains from amino acids by translating mRNA

what does the rough endoplasmic reticulum do

folds and transports proteins

if a protein is destined to be secreted, the ribosome synthesizing it is usually attached to the rough endoplasmic reticulum rather than being free in the cytosol. the environment inside the rough ER allows for the correct folding of the newly formed peptide chain before being passed to the golgi apparatus

what does the transport vesicle do

transports proteins

a transport vesicle containing the protein buds off the rough ER and travels to the golgi appratus. the vesicle fuses with the golgi membrane and releases the protein into its lumen

what is lumen

the inner, open space or cavity within a tubular structure, organ, or cell

what is the role of the golgi apparatus

modifies and packages proteins

proteins can have chemical groups (eg sugar molecules) added or removed at the golgi apparatus, where they are often packaged into secretory vesicles for export, or directly released into the cytosol for use by the cell

what is the role of the secretory vesicle

transports proteins

secretory vesicles containing proteins for export bud off the golgi apparatus and travel through the cytoplasm, fusing with the plasma membrane. this releases the proteins contained from within into the extracellular environment through the process of exocytosis