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What are the major similarities among phagocytosis, pinocytosis, and receptor-mediated endocytosis?
•Take in large molecules/particles or take in groups of molecules
•Require cellular energy (ATP)
What are the major differences
among these 3 processes ?
- •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
What are the RNA subunits?
What is the RNA sugar?
ribose (OH attached to C #2)
Explain RNA shape.
- variable, depending on type
- eg: straight or folded
- no alpha-helix
- when folded, the shape is maintained by base-pairing
Length of RNA in relation to DNA
smaller in length
Types of RNA
- small nuclear RNA
- heterogeneous nuclear (hnRNA)
General function of RNA:
collectively, all of the biochemical reactions occurring in an organism
a chemical reaction that occurs in an organism
the capacity to do work and cause change; exists in different forms and can be converted from one to another
Types of energy
1st Law of Thermodynamics
- 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
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
- 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
2nd Law of Thermodynamics
- 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.
Energy that is supplied from exergonic reaction does what?
couples the exergonic and endergonic reactions so energy from exergonic drives endergonic
Write out the structure of ATP.
phosphate-phosphate- phosphate- ribose- adenine
Hydrolysis of ATP:
ATP + H2O --> ADP + phosphate + energy
the initial investment of energy for starting a reaction; the energy required to break bonds
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)
Although exergonic reactions are spontaneous, they need a little push. What is this push?
energy that supplies this push in Gibb's free energy
What is the connection between EA and energy released.
- no connection
- only connection is if EA is high, its a slow reaction
Points of enzymes.
- 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
In cells, a vast majority of catalysts are __, but some can be __.
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
Two ways active site and substrate might fit
- lock and key model (perfect fit/ match exactly)
- induced-fit model (most common)
Types of bond between enzymes and substrate
due to speed of reaction, it may form H bonds or ionic bonds
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
- 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
Enzymes exhibit a property called __
a series of biochemical reactions that are linked together with the products becoming reactions
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
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)
Chemicals that affect allosteric enzyme activity
- activator (modulator, effector [positive])
The binding between an activator or inhibitor and its allosteric enzyme is usually __.
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
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
Multicellular organisms= __
Resolution of __ is better than in __.
The __ the # of resolution, the __ the resolution.
- eye: __
- LM: __
- 100 um
- .2 um
- 0.002 um (best res)
- not all cells are the same size
- largest cell: ostrich egg
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
- the living material or substance of a cell (cell wall not included)
- Divided into nucleus and cytoplasm
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
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
- 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
- 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
Proteins within the membrane are __.
What is the function of carbs (oligosaccharides) on the membrane?
- cell-cell recognition
Why do phospholipids rarely flip-flop?
- hydrophobic tails will be exposed oto the aqueous solution
- hydrophilic has to go through hydrophobic
- compartmentalization: forms boundary around cell; barrier; separates environment from inside membrane;
- detects outside info
- controls movement of csubstances inside/ outside cell
What moves via facilitated diffusion?
polar substances, amino acids, sugars, H2O
- movement of ORGANIC molecule AGAINST concentration gradient
- no energy required due to potential energy of particle diffusing down
Due to __, anything above __ moves.
Its vibration movement is the __.
- heat (thermal energy)
- absolute zero
- Brownian motion
difference in voltage on opposite sides of membrane (electrochemical gradient)
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
How are enzymes used in food processing?
- fermenting beer and wine
- making bread dough
- creating flavors and products
- preserve quality