Exam (elaborations)
BIL 255 TOPIC 6 PROTEINS EXAM
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BIL 255 TOPIC 6 PROTEINS EXAM....
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proteinsworkhorses of cell metabolism
proteome
the entire set of proteins expressed by a genome
either a cell's or a whole organism's
interactive insights
the expanding interactive has helped researchers show that pathogen effectors
target highly connected plant proteins, most likely to control the host's cellular
machinery
objectives of this section
Review their structure
Primary, secondary, tertiary, quaternary
Protein folding mechanisms - chaperones
degradation/turnover - proteasomes
Look at molecular motors
Analyze enzyme kinetics
molecular structure of proteins
primary (sequence)
secondary (local folding)
tertiary (long range folding)
,quaternary (multimeric organization)
supramolecular (large scale assemblies)
regulation, structure, movement, catalysis, transport, signaling
proteins are classified
functionally
enzymes
catalytic activity and function
transport proteins
bind and carry ligands
storage proteins
ovalbumin, gluten, casein, ferritin
contractile (motor)
contract, change shape, elements of cytoskeleton (actin, myosin, tubulin)
structural (support)
collagen of tendons and cartilage, elastin of ligaments (tropoelastin), keratin of
hair, feathers, and nails, fibroin of silk and webs
defensive (protect)
antibodies (IgG), fibrinogen and thrombin, snake venoms, bacterial toxins
regulatory (signal)
regulate metabolic processes, hormones, transcription factors and enhancers,
growth factor proteins
receptors (detect stimuli)
light and rhodopsin, receptor proteins and acetylcholine or insulin
enzyme
,catalyzes covalent bond breakage or formation
Living cells contain thousands of different enzymes, each of which catalyzes
(speeds up) one particular reaction.
Examples include: tryptophan synthetase— makes the amino acid tryptophan;
pepsin—degrades dietary proteins in the stomach; ribulosebisphosphate
carboxylase—helps convert carbon dioxide into sugars in plants; DNA
polymerase—copies DNA; protein kinase—adds a phosphate group to a protein
molecule.
structural protein
provide mechanical support to tissues and cells
Outside cells, collagen and elastinare common constituents of extracellular
matrix and form fibers in tendons and ligaments. Inside cells, tubulin forms
long, stiff microtubules and actin forms filaments that underlie and support the
plasma membrane; α-keratin forms fibers that reinforce epithelial cells and is
the major protein in hair and horn.
transport protein
carries small molecules or ions
Inthebloodstream,serumalbumincarries lipids, hemoglobin carries oxygen, and
transferrin carries iron. Many proteins embedded in cell membranes transport
ions or small molecules across the membrane. For example, the bacterial protein
bacteriorhodopsin is a light- activated proton pump that transports H+ ions out
of the cell; the glucose carrier shuttles glucose into and out of liver cells; and a
Ca2+pump in muscle cells pumps the calcium ions needed to trigger muscle
contraction into the endoplasmic reticulum, where they are stored.
motor protein
generates movement in cells and tissues
Myosin in skeletal muscle cells provides the motive force for humans to move;
kinesin interacts with microtubules to move organelles around the cell;
dyneinenables eucaryotic cilia and flagella to beat.
, storage protein
stores small molecules or ions
Iron is stored in the liver by binding to the small protein ferritin;ovalbumin in
egg white is used as a source of amino acids for the developing bird embryo;
casein in milk is a source of amino acids for baby mammals.
signal protein
carries signals from cell to cell
Many of the hormones and growth factors that coordinate physiological
function in animals are proteins; insulin, for example, is a small protein that
controls glucose levels in the blood; netrin attracts growing nerve cells in a
specific direction in a developing embryo; nerve growth factor (NGF)
stimulates some types of nerve cells to grow axons; epidermal growth factor
(EGF)stimulates the growth and division of epithelial cells.
receptor protein
detects signals and transmits them to the cell's response machinery
Rhodopsin in the retina detects light; the acetylcholine receptor in the
membrane of a muscle cell receives chemical signals released from a nerve
ending; theinsulin receptor allows a liver cell to respond to the hormone insulin
by taking up glucose; the adrenergic receptor on heart muscle increases the rate
of heartbeat when it binds to adrenaline.
gene regulatory protein
binds to DNA to switch genes on or off
the lactose repressor in bacteria silences the gene for the enzymes that degrade
the sugar lactose; many different homeodomain proteins act as genetic switches
to control development in multicellular organisms, including humans
special purpose protein
highly variable
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