Midterm #1 Flashcards
Primary Structure
- Linear sequence of amino acids
Peptide Bonds
- Functions
- Picture
- Holds together adjacent amino acids in polypeptide chain
- Polar nature around peptide bond
Secondary Structures
- 2 examples
- Alpha-helix or Beta sheet
- Alpha-Helix proteins
- Myoglobin has almost all alpha helices
- Hydrogen bonds hold alpha helices together
- Beta sheet proteins
- Antibodies and Tcell receptors largely from beta sheets
- Most proteins have both
Tertiary Structure
- What it is
- 5 examples
- 3D shape of polypeptide chain
- Polar/Nonpolar Interactions
- Hydrophobic aa point inward
- Hydrophillic aa point outward
- One of most important features in determining tertiary structure in proteins
- Hydrogen Bonds
- Van der Waals Forces
- Significant when many atoms can line up closely
- Most important in nonpolar amino acids
- Ionic Interactions
- Certain amino acid in ionic form
- Example: glutamate
- Disulfide Bonds
- Secreted proteins only
- Inside cell=reducing environment/disturb bond
Quaternary Structure
- Contain 2 or more polypeptide chains
- Each polypeptide chain=subunit
- Example: hemoglobin, 4 subunits
- Example: collagen, 3 subunits
Prosthetic Groups
- nonprotein group forming part of or combined with a protein
- Example: myoglobin and prosthetic group heme
Why do hydrogen bonds form so frequently in polypeptide chains?
- Oxygen and nitrogen in peptide bond
- Polar region in peptide bond
- Hydrogen bonds form due to the mutual of attraction of two such oppositely charged regions
Specific Binding
- Importance
- Specificity based on… (4 things)
- Function of almost all proteins is based on their specific binding of other molecules
- Specificity based on several features
- Complementary shape of protein and ligand
- “Lock and Key”
- Polar/Nonpolar interactions
- Electrostatic attraction
- Hydrogen bonding
- Complementary shape of protein and ligand
Allosteric Regulation
- Regulatory molecule bind site OTHER THAN catalytic site
- Cause 3D shape change
Protein Kinase
- Picture
- What works by activating protein kinases?
- Transfers phosphate from ATP to protein
- Hormones and most growth factors work by activating a protein kinase
Protein Phosphatase
- Removes phosphate group
- Return protein to original state
GTP Binding Proteins
- Picture
- Active vs. Inactive States
- Important in the action of many hormones and other physiological regulatory molecules
- Active=GTP, Inactive=GDP
- Reactivated by GTP replacing GDP on the molecule
Protein Secretion Sequence
- Picture
- Proteins synthesized at ribosome
- For use in cell, ribosome in cytosol
- Secreted: 1st amino acids in polypeptide=signal sequence
- Signal sequence made
- Synthesis stops
- Ribosome dock at rough endoplasmic reticulum
-
Protein threaded into RER
- Signal sequence cleaved
- Enzymes cut proteins elsewhere, most secreted proteins modified
-
Vesicles with protein bud from RER
- move to the Golgi apparatus
- Fuse to first pita stack
- Vesicles bud off and add to other pita stacks
- At other end of Golgi, secretion vesicles bud off
- Move to plasma membrane
- Attach and release via exocytosis
- Often need signal for release
Secretion of Collagen
- Picture
Made in fibroblast
- 3 tight packed polypeptide chains, linear and stiff
- 3 chains synthesized separately
- Wind around each other in RER
- Procollagen with tangled ends
- Relatively soluable
- If aggregate in cell, fatal
- Secreted from secretion vesicles into a groove at the surface of the cell
-
Procollagen proteinases cleave tangles
- Forms tropocollagen
- Less soluable and straight
- Start adhering to each other within the groove
- Form fibrils
- Spun out of the groove
- Crosslinked into strong fibers
Glycoproteins
- Proteins with carbohydrates added
- Called glycosylation
- Some in RER, most in Golgi
- Makes polar, stable, soluable (Ex: Growth hormone)
- Also hold more water (Ex: mucus)
Proteoglycans
- Picture
- Structure/Part
- Two places found
- Properties
- Carbohydrate glycoaminoglycans (GAGs) added
- Monosaccharides are linear
- GAGs along protein core to form “bristle brush”
- GAGs highly negative charge
- Often aggregate into huge complexes by adding to long linear molecule (Ex: hyaluronan)
- Take up lots of water, make gel like
- In the interstitial fluid
-
Cartilage has proteoglycans, strength from collagen
- Proteoglycans make it shock absorbing and springy (Ex: intravertebral discs)
How do newly synthesized membrane proteins wind up embedded in the plasma membrane?
- The new membrane proteins thread into the RER membrane as they are being synthesized
- The membrane of the endoplasmic reticulum moves through the Golgi apparatus and becomes a secretion vesicle
- Secretion vesicle fuses with the plasma membrane, the newly synthesized membrane protein is added to the plasma membrane.
Membrane Proteins
- Endocytosis
- Endosomes
- Picture
- removed from the plasma membrane and then returned in a relatively short time
- Removed through endocytosis
- Fuse with a larger, membranous structure called an endosome
- Budding from endosome, vesicles can bind to plasma membrane
- Endosome=quick means of forming new secretion vesicles
Filling Orbital Shells
- first shell closest to the nucleus has only one orbital
- 2 e-
- next two shells have four orbitals
Amphipathic
Both a polar region and a nonpolar region coexisting in the same molecule
Why We Breathe Oxygen
- Serves as a repository for all those electrons that have lost energy in the process of generating ATP
- Electron from C-H to O-H in water, less energy
First Law of Energetics
- energy is conserved
- energy transformed, but total amount of enery stays the same
- Quantity
Second Law of Energetics
- Quality
- Order→Disorder
- entropy of the system increases with time
- less ordered system with time
- Reactions can occur if there is an increase in entropy
- Mostly heat, some more molecules
- capable of powering work or synthesis
- Negative free energy change
- -delta G
- “spontaneous”
- coupled reactions if overall negative free energy change
- factor causing a negative free energy change is almost always a net release of heat
- Glucose+oxygen=more molecules and heat
Flow of Energy Through Body
- As it flows through the body, chemical synthesis and work are possible.
- Energy leaves the body in the disordered form of heat at body temperature
- May or may not be a net change in the amount of energy stored within your body
Rate of Energy Expenditure
- Definition
rate at which carbohydrates, fats and proteins are broken down.
Direct Measurement of Energy Expenditure
- proper energy unit
- Energy measured by heat
- Rate at which heat is formed
- kcal/min
- amount of heat energy required to heat one kilogram of water one degree Celsius
- equal to a dietary calorie
- proper energy unit kjoule
- equal to 0.24 kilocalories
- Theoretically correct method of measurement
- Not practical
Indirect Measurement of Energy Expenditure
- Measure how fast body uses oxygen
- one glucose to carbon dioxide and water, exactly six oxygen used
- 4.8 kcal/l O2
- typical mix of carbohydrates, fats and proteins
MET
- metabolic equivalent (MET)
- 1.0 kcal/hr per kg
VO2Max
- Over 15 min, more work required until go no further
- Measure O2 at that point
- mL O2/min*kg
- Brief periods: ATP can be generated without use of oxygen in mitochondria
- Longer periods: rate at which ATP is generated is directly proportional to the use of oxygen
- depends on size, genetics and level of training for endurance exercise
- older patients found that VO2max is one of the best predictors of mortality
Respiratory Quotient (RQ)
- Equation
- Only carb, only fat, mixture
- Double labeled water technique
- RQ = carbon dioxide released/oxygen consumption
- Only carb, RQ=1
- Fats, RQ=0.7
- RQ=0.8-0.9
- Doubly labeled water technique
- water with rare isotopes of both oxygen and hydrogen
- rate at which both isotopes disappear from the body is followed
- Loss of H: loss of water in urine
- Loss of O: rapid loss of CO2
- Ratio: allows a calculation of the rate at which carbon dioxide is being produced and exhaled from the body
Carbonic Anhydrase
- Responsible for rapid oxygen to carbon dioxide in labelled water experiment
- In RBC
- CO2 + H20 <—> H+ + HCO3-
- fastest enzyme in the body
Reactions With Glucose
- Picture
- Rate Limiting Factor
- O2 delivery to muscles
- Run glycolysis, make lactic acid
- Lactic threshold=anaerobic threshold
- Acidity of blood increases, respiratory things go on
- Oxidative Phosphorylation
- Make ATP, add e- to O2
Water Polar Covalent Bonds
- Polar molecules attract a layer of water around them
- C and H share e- really well
- O and N attract e- more (polar covalent bonds)
Water Solvent Properties
Like dissolved like
Water Hydrogen Bonding
- Adjacent water molecules attract one another
- In liquid, transient bonds
- High surface tension
- Important in respiratory physiology
Fatty Acids: Saturated and Unsaturated
- nonpolar molecules
- oxygen and a hydroxyl group at one end
- Saturated
- All single bonds
- linear
- Unsaturated
- One or more double bond
- Bent, locked carbons, “kink”
- Classified by location of double bond from end of molecule without oxygens
- Ex: n-3 or omega-3
Cis/Trans Fatty Acids
- Double bond cannot rotate
- “kink”
- Cis=more pronounced bend
- Cis fatty acids not solidify as readily
- Cis isomers cannot line up next to one another
- Trans=naturally uncommon
- when polyunsaturated fatty acids from plants are “partially hydrogenated” chemically
- make solid and improve shelf life
- Increased risk of heart disease
n-6 and n-3 Fatty Acids
- electrical excitability
- polyunsaturated fatty acids
- Can serve competing functions
- Body doesn’t make, so you eat them
- essential fatty acids
- Plant and plant oil
- alpha lineolic acid from soybean, canola, flaxseed and walnut oils
- n-6=linoleic acid
- make to arachidonic acid
- made into eicosinoids (regulatory)
- paracrine, act locally
- n-3=alpha linoleic acid
- EPA and DHA
- Fish oil
- paracrine
- Appropriate stimulus, the fatty acid is freed and then converted into a certain paracrine
- Directly affect opening and closing of ion channels and thus the electrical excitability of membranes
- cardiac arrhythmias
Triacylglycerols
- Picture
- three fatty acids joined together by one glycerol molecule
- adipose tissue, plant oils
- unsaturated fatty acids in triacylglycerol makes it more fluid
- Triacylglycerols are sometimes referred to as triglycerides
Phospholipids
- 2 ends to molecule
- polar/nonpolar
- amphipathic
- membranes
- see figure for parts
- “small polar”-ex: choline
- keep happy through micelle and bilayer
- break surface tension, ex: soap, in lungs
Cholesterol
- lipid molecule
- compact/rigid
- insoluable
- only 1 oxygen
- plasma membranes
Derivatives of an n-6 Polyunsaturated Fatty Acid
- Regulatory molecules from n-6 arachidonic acid
- 20 carbons
- Polyunsaturated
- eicosanoids
- defense against damage and pathogens
- inflammation and hemostasis
PLA2
- Stimuli activates membrane enzyme called phospholipase A2
- Ex: condition that causes, or threatens to cause, tissue damage
- acts on a membrane phospholipid
- Arachidonic acid now substrate
COX1, COX2
- cyclooxygenase
- produce a regulatory molecule that is either a prostaglandin or a thromboxane
- bend arachidonic acid into a hairpin
- All cells have different “further enzymes”
COX1
- normally present
- normal physiology
- inhibit stomach secretions (prostaglandins)
COX2
- Not normal physiology
- Threaten tissue damage
- Inflammation
- Induced
- TNF-alpha and IL-1 induce COX2
- Inhibited by glucocorticoid steroids
- COX2 specific inhibitor
- Cardiovascular repercussions
- Some removed, others used sparingly
LOX
- inhibitor
- lipoxygenase (LOX)
- regulatory molecules in the family of the leukotrienes
- Inflammatory
- Hay fever, asthma, ibuprofen not work
- LOX inhibitor
- Zileution
- monteleukast, prevent leukotrines from binding receptor
- eicosanoid regulatory molecules=paracrines
- degraded too rapidly
COX Inhibitors
- nonsteroidal anti-inflammatory drugs (NSAIDS)
- aspirin, ibuprofen, and naproxen
- celecoxib, selectively act on COX2
- rofecoxib removed because of cardiovascular repercussions
- Aspirin
- covalently modifies COX
- mall amounts of aspirin affect platelets for more than a day
- platelets moving through the intestines have their COX permanently blocked
- platelets lack a nucleus, new COX forms only with the synthesis of new platelets
- related to NSAIDs, acetaminophen
- supresses pain and fever
- little effect on inflammation and the secretion of stomach acid
Derivatives of n-3 Polyunsaturated Fatty Acids
- beginning with EPA and DHA
- incorporated into membrane phospholipids and then released into the membrane
- Released by PLA2
- Much less understood
- interfere with arachidonic acid binding w/ COX and LOX
- Resolve inflammation
- can affect the electrical excitability of cardiac muscle cells
How To Move Fat
- Break down TAG and release FA
- Very small amount soluable in blood
- FA bind to transporter to get into the tissue
- increase by exercise and cold exposure
Lipoprotein Structure
- Not molecules, they are a particle
- Solve lipid/water soluabilty by utilizing amphipathic nature of phospholipids
- single layer of phospholipid molecules on their outside, surrounding a central core
- outside of the phospholipid molecule is polar/water compatible
- nonpolar portion inside, compatible with nonpolar core of lipoprotein
- esterified cholesterol
- super nonpolar cholesterol
- Fatty acid on the oxygen
- normal cholesterol is found in the outer layer of phospholipid
- outer layer, protein molecule, apolipoprotein
- amphipathic, stabilizer
- Each lipoprotein identified through differing apolipoprotein
Lipoprotein Movement
- Some transport dietary lipids from the small intestine to adipocytes and the liver
- Some transport cholesterol between different part of the body
- At target cell:
- apolipoprotein binds to a receptor
- lipoprotein taken up by receptor mediated endocytosis
- Sometimes enzyme on capillary wall, lipoprotein lipase
- unloads triacylglycerol
- breaks TAG into FAs and glycerol
HDL and LDL
- LDL
- liver to cell
- HDL
- back to liver
- differentiated by apolipoprotein
Immune Cells Using Phagocytosis
- 4 of them
- Neutrophils
- abundant in the blood, quickly enter tissues, and phagocytize pathogens in acute inflammation.
- Macrophages
- related to monocytes in the blood. These longer-lived cells predominate in chronic inflammation. They also release some important inflammatory paracrines
- IFN-gamma increase macrophage production of superoxide, type 2 interferon
- Dendritic Cells
- elaboration of a specific immune response rather than for directly destroying the pathogens
- B Lymphocytes
- small amount of phagocytosis in these cells is often necessary in order for them to develop into cells that release antibodies
Phagocytosis: Sequence of Events
- lysosome derived from
- neutrophil or macrophage flowing around the pathogen and engulfing it
- enclosed in a phagosome
- fusion of lysosomes with the phagosome
- forms phagolysosome
- Lysosome derived from Golgi
The Dangers of Oxygen
- Electrons from food to NADH or NADPH
- Need oxygen to put electrons and form water
- Oxygen is electron garbage can
- Each step of electron transport chain hold electron just a little tighter
- Take a little energy at each step and form ATP
- One electron in an orbital, form a radical
- Small amounts made in metabolism
- Highly reducing and can cause tissue damage
- 21% of air, not full of water we would burn up
Destruction of Microbes: Oxygen Radicals
- Overview
- phagocyte oxidase in membrane of phagolysosome
- generate oxygen radicals
- single electrontaken from NADPH and added to oxygen
Destruction of Microbes: Nitric Oxide
- Nitric oxide synthase synthesizes nitric oxide
- reacts with superoxide to create further molecules that damage biological molecules
Destruction of Microbes: Anti-Microbial Proteins
- 2 Specific Examples
- Lysosomes contain several proteases
- broad spectrum enzyme elastase
- important or even essential for killing various bacteria
- lysozyme
- attack gram+ cell wall
Destruction of Microbes: Anti-Microbial Peptides
- Defensins attack bacterial membranes
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Destruction of Microbes: Binding Proteins
- Lactoferrin binds iron
- Another binds vitamin B12