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DesLee26
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What are the major similarities among phagocytosis, pinocytosis, and receptor-mediated endocytosis?
•Membrane-bound vesicles
•Take in large molecules/particles or take in groups of molecules
•Require cellular energy (ATP)
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What are the major differences
among these 3 processes ?
- Phagocytosis:
- •Pseudopodia
- •Takes in large particles
- Pinocytosis:•No pseudopodia
- •Takes in fluid
- •Not specific
- •Depression forms “naked” vesicle
- Receptor- Mediated Endocytosis•No pseudopodia
- •Very specific: receptors on membrane
- •Coat protein on inner side of membrane
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What are the RNA subunits?
ribonucleotides
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What is the RNA sugar?
ribose (OH attached to C #2)
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Explain RNA shape.
- variable, depending on type
- eg: straight or folded
- no alpha-helix
- when folded, the shape is maintained by base-pairing
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Length of RNA in relation to DNA
smaller in length
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Types of RNA
- mRNA
- rRNA
- tRNA
- small nuclear RNA
- heterogeneous nuclear (hnRNA)
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General function of RNA:
protein synthesis
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metabolism
collectively, all of the biochemical reactions occurring in an organism
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Biochemical reaction
a chemical reaction that occurs in an organism
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Energy
the capacity to do work and cause change; exists in different forms and can be converted from one to another
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Types of energy
- heat
- light
- mechanical
- chemical
- nuclear
- electrical
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1st Law of Thermodynamics
Application?
- The total energy in the universe is constant; energy can be neither created or destroye, only transformed from one form to another
- - In a chemical (or biochemical reaction), the reactants and products rarely contain the same amount of energy, but the amount of energy on both sides of the reaction must be the same
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2 classes of reactions:
- exergonic: reactants contain more energy than the products (spontaneous/ downhill)
- A + B --> C + D + energy
- endergonic: reactants contain less energy than the products
- energy + A + B --> C + D
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Free energy
- the energy available in any particular system to do useful work; in cells, the energy released in an exergonic reaction is never all free energy
- e.g. A + B --> C + D + free energy + heat
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2nd Law of Thermodynamics
Applications
- All physical and chemical change proceeds to that the total entropy of the universe increases to the maximum possible; entropy of the universe never decreases, which means that free energy decreases
- Althoiugh the universe is disorganized, the system may be organized. The part that supplies the energy (sun) is getting more disordered.
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Energy that is supplied from exergonic reaction does what?
couples the exergonic and endergonic reactions so energy from exergonic drives endergonic
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Write out the structure of ATP.
phosphate-phosphate- phosphate- ribose- adenine
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Hydrolysis of ATP:
ATP + H2O --> ADP + phosphate + energy
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Activation Energy
the initial investment of energy for starting a reaction; the energy required to break bonds
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How do catalysts work?
- work by lowering activation energy needed for reaction to occur
- almost all biochemical reactions are catalyzed
- most catalysts in organisms are enzymes (proteins)
- RNA may act as a catalyst for a few biochemical reactions (ribozyme)
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Although exergonic reactions are spontaneous, they need a little push. What is this push?
energy that supplies this push in Gibb's free energy
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What is the connection between EA and energy released.
- no connection
- only connection is if EA is high, its a slow reaction
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Points of enzymes.
- Globular
- Simple or conjugated
- May/ may not have quaternary structure
- May or may not have cofactor
- ends in -ase
- can, in most cases, catalyze a reaction in either direction depending on relative concentrations; does not determine which direction
- reactants in enzyme catalyzed reactions= substrates
- enzymes differ in specificity
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In cells, a vast majority of catalysts are __, but some can be __.
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Explain enzyme specificity.
can be very specific, such as urease, which only catalyzes urease; or can have small specificity, for example, ligase, which catalyzees several lipid- involving reactions
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Two ways active site and substrate might fit
- lock and key model (perfect fit/ match exactly)
- induced-fit model (most common)
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Types of bond between enzymes and substrate
due to speed of reaction, it may form H bonds or ionic bonds
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Some ways that an enzyme might help speed a reaction:
- bring substrates close together
- orient substrates correctly for a reaction to occur
- strain/ weaken bonds in substrates so ehtey are more likely to break
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Inhibitors
- competitive: similar to substrate's structure; compete for active site, but does not change shape of active site; may/ may not permanently bind
- non-competitive: don't resembe substrate structure; bind to place other than active site and change shape of enzyme
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Enzymes exhibit a property called __
saturation kinetics
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Biochemical pathways
a series of biochemical reactions that are linked together with the products becoming reactions
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Characteristics of control mechanisms
- 1) must control rates of enzyme-catalzyzed reactions
- 2) should prevent waste of energy and materials
- 3) must function efficiently and without interruption
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Control or regulation by allosteric enzymes
allosteric enzyme: enzyme usually composed of 2 or more polypeptide chains that exists in two phsyical shapes with one or mroe allosteric sites (active/ inactive)
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Chemicals that affect allosteric enzyme activity
- activator (modulator, effector [positive])
- inhibitor
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The binding between an activator or inhibitor and its allosteric enzyme is usually __.
reversible
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What is the modern cell theory?
- 1) all organisms are composed of cells
- 2) the cells come from pre-existing other cells
- 3) the structure of cells is related to their function
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Resolution
a physical measure of how close two objects can be and still be seen as distinct objects; measured in units, such as mm, um, nm
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Multicellular organisms= __
cell specialization
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Resolution of __ is better than in __.
The __ the # of resolution, the __ the resolution.
Comparison
- eye: __
- LM: __
TEM: __
- EM
- LM
- smaller
- greater
- 100 um
- .2 um
- 0.002 um (best res)
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Size
- not all cells are the same size
- largest cell: ostrich egg
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Reason for smallness of cells
- surface area/ volume ratio
- nuclear control over cell metabolism: nucleus sends out chemicals/ molecules to carry out functions and its advantageous if the molecules/ chemicals don't have to travel as far to leave the nucleus
- lower limit to cell size
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Protoplasm
- the living material or substance of a cell (cell wall not included)
- Divided into nucleus and cytoplasm
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Cytoplasm can be defined in two ways: __
- - all parts of the protoplasm except the nucleus: sub-cellular organelles and cytosol [equivalent to cytosol]
- - physical nature of the cytosol
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True or False:
Only some cells, no matter what kind, have a membrane on the surface of the protoplasm; eukaryotic cells and some prokaryotic cells also have internal membranes
- False:
- Only some cells, no matter what kind, have a membrane on the surface of the protoplasm; eukaryotic cells and some prokaryotic cells also have internal membranes
- True:
- All cells, no matter what kind, have a membrane on the surface of the protoplasm; eukaryotic cells and some prokaryotic cells also have internal membranes
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Proteins within the membrane are __.
globular
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What is the function of carbs (oligosaccharides) on the membrane?
- cell-cell recognition
- adhesion
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Why do phospholipids rarely flip-flop?
- hydrophobic tails will be exposed oto the aqueous solution
- hydrophilic has to go through hydrophobic
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Membrane functions
- compartmentalization: forms boundary around cell; barrier; separates environment from inside membrane;
- detects outside info
- controls movement of csubstances inside/ outside cell
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What moves via facilitated diffusion?
polar substances, amino acids, sugars, H2O
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Explain cotransport.
- movement of ORGANIC molecule AGAINST concentration gradient
- no energy required due to potential energy of particle diffusing down
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Due to __, anything above __ moves.
Its vibration movement is the __.
- heat (thermal energy)
- absolute zero
- Brownian motion
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membrane potential
difference in voltage on opposite sides of membrane (electrochemical gradient)
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Why do fruites ripen? What is done?
- action of enzymes
- prseervation techniques that have been developed to half the action of natural enzymes and prevent spoilage
- involves freezing, drying, or blanching
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How are enzymes used in food processing?
- fermenting beer and wine
- making bread dough
- creating flavors and products
- preserve quality
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