Biology Exam 2: Cells, Metabolism, Respiation, Photosynthesis
Terms
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- Metabolism
- sum total of all chemical reactions occurring in the cell in an organism
- Catabolism
- one of the components of metabolism: metabolic pathways that release energy by breaking down complex molecules into simpler compounds (ex. cellular respiration)
- Anabolism
- Metabolic pathways that consume energy by building complex molecules from simpler ones
- Energy
- the capacity to do work
- kinetic energy
-
energy of motion
: one of fundamental types of energy - potential energy
-
energy that matter possesses because of its structure or location
: one of fundamental types of energy - chemical energy ( not one of two basic fundamental energies)
- type of kinetic energy: stored i nmolecules because of the structural arrangement of the atoms in those molecules
- are the basic types of energy interconvertible?
- yes
- Free energy
- that portion of a system's energy that is available to perfom work
- are free energy and process sponaneity related?
- yes
- a spontaneously occurring process will always involve...
- a loss of free energy ( delta G will be negative : energy is released)
- processes that DO NOT occur spontaneouly require...
- an input of energy if they are going to occur ( delta G will be positive: energy increases)
- Exergonic
- free energy is released during reaction
- Endergonic
- free energy is absorbed during reaction
- are exergonic and endergonic reactions coupled in metabolism?
- yes
- ATP
-
Adenosine Triphophate
Contains potential chemical energy
- the molecule that is used to carry out most cellular work - what ultimately allows work to be performed?
-
the hydrolysis of the phosphate bonds is an exergonic reaction that is coupled to endergonic reactions
: ex : active transport, ATP hydrolysis, changes in protein shape (confirmation)
8.14 - Mechanical work
-
changes in shape ; movement
: one of 3 basic types of cell work - transport work
-
movement of substancecs across the embrance against the concentration gradient
:1 of 3 cell work - chemical work
-
pushing of endergonic reactions )in most cases this pushing coupled o exergonic reactions)
: 1 of 3 cell work - Enzymes are what?
- protein catalysts
- catalyst
-
an chemical agent (like protein) that changes the rate of how fast a chemical reaction occurs withouth being consumed in the reaction
:does not change spontanaeity - enzymes work by lowering what?
-
energy of activation in a chemical reaction
: this increases the rate of the reaction (ho fast occurs) so that the normal metabolism of the cell cna be maintained; however, enzymes do not have capacity by themselves to make nonspontaneous reactions occur (this requires energy) - enzymes allow less energy to activate reaction
- goes from high energy to low energy and reuses recycled enzymes
- enzymes are substrate specific
- 3D fit between an enzyme and its substrate and "induced fit"
- induced fit
- a slight change in the active site of a protein upon binding of substrate such that the binding affinity is increased
- active site
-
key part:
where the chemistry occurs
:catalytic center of enzyme
:part(s) of the substrate molecule(s) to be effected are held in close proximity - will the internal environment of the cell affect enzyme activity?
-
yes
:important environmental factors include:
pH (acidity), temperature, cofactors like vitamins -
Control of Metabolism:
Competitive Binding - a molecule that directly affects active site by competitive binding will have an overall shpare tha tis similar to the substrate
-
Control of Metabolism:
Noncompetive Binding - indirectly affects active site by binding a site away from the active site, but overall protein shape is changed as is the conformaion of the active site
-
Control of Metabolism:
Allosteric Regulation - allosteric enzymes are typically composed of several subunits; binding to the allosteris sie )away from the active site) may simultaneously change all active sites of the individual subunites such that the enzyme is activated or inhibited
-
Control of Metabolism:
Cooperativity - binding of a single substrate molecule to one of several subunits results in induced fit and activation of active sites on other subunits
-
Control of Metabolism:
Notes - Feedback inhibition of a metabolic pathway - localization of enzymes w/in the cell
- Cellular Respiration
- metabolic process by which organisms convert the energy present in organic molecules to ATP and byproducts
- Glucose: Summary Equation
- Organic Molecule + Oxygen = CO2 + H2O + ATP + HEAT
- mitochondrial structure
- outer membrane, inner membrane, intermembrane space, matrix
-
3 parts of cellular respiration:
oxidative phophorylation - generates most of the ATP
-
3 parts of cellular respiration:
glycolysis - occurs in the cytosol; generates 2 ATP and some high energy molecules (2 NADH) that will drive oxidative phosphorylation
-
3 parts of cellular respiration:
krebs cycle - occurs in the mitochonrial matrix; generates some ATP(2) and alot of high energy molecules (10) that will be used to drive oxidative phos.
- oxidative phosphorylation
- Oxidation/Reduction reactions and the pumping of protons across the inner membrane of the mitochondrion
- Oxidation/Reduction (Redox) Reactions
- involves the transfer of electrons from one molecule to another
- oxidized
-
the molecule that losses electrons:
(LEO, loss of electrons is oxidation - reduced
-
the molecule that gains electrons:
GER = (Gain of electrons is reduction) - X(e-) + Y ------------> X + Y(e-)
- in this example, molecule X is the reducing agent (which is oxidized) and molecule Y is the oxidizing agent (which is reduced)
- when electrons are transferred between molecules they lose ...
- some enrgy with each transfer
- what are pumped from matrix side of the mito to the inner membrane side by a hydrogen-electron transport chain (HETS)?
- protons (H+)
- HETS
- series of proteins located within or on the inner membrane that function in a series of redox reactions
- as e- move through the HETS chain they progressively ...
- lose energy,
- some of this energy is used to transport WHAT across the membrane?
- H+
- when a protein in the chain receives e- (is reduced) it gains energy, but losses energy when it is oxidized
- the HETS is a series of exergonic and endergonic reactions that are coupled
- certain proteins in the HETS will use the free enrgy that accompanies the redox reaction to do WHAT?
- to transfer eletrons across the inner membrane
- In the HETS, the proteins are organized in such a way that there is a...
- continnuum of increasing electronegativity; this results in the orderly flow of electrons “downhill†toward a terminal electron acceptor (oxygen)
- The initial electron donors in oxidative phosphorylation are...
- high energy reducing agents that are generated in the Krebs cycle and in Gylcolysis
- How many reducing agents are used??
- 2: (NADH, and FADH2 are used)
- How many protein complexes comprise the HETS?
- 3: (NADH-Coenzyme Q Reductase, Coenzyme Q -Cytochrome C Complex, Cytochrome C Oxidase Complex)
- Do electrons flow sequentially through these complexes?
- Yes
- each complex is comprised of many ...
- proteins, but only a few of these proteins actually function in the transfer of protons across the inner membrane
- these electrons are transferred through the complxes with a particular # of H+ being transfered by some of the proteins of the respective complexes
-
NADH-Coenzyme Q Reductase - 4H+
Coenzyme Q -Cytochrome C Complex - 6H+
Cytochrome C Oxidase Complex - 2H+ - Note that each NADH transfers 2e- through each of these complxes and is therefore responsible for the movement of 12H+ across the inner membrane
-  In contrast FADH2 initially donates 2e- to Coenzyme Q -Cytochrome C Complex and is ultimately responsible for the movement of 8e- across the membrane
- Note that oxygen is the terminal electron acceptor in the formation of water
- 2e- + 2H+ + 1/2O2 ------> H2O
- protomotive force
-
The proton gradient that results
pmf = concentration gradient + charge speration (voltage potential)
*most of the potential energy of the protomotive force is embodied in the charge potential -
Use of PMF to Generate ATP:
ATP Synthase Complex (mitochondrial lollipops) - a large complex of protiens that has two major components (a stem called Fo and a head called F1 that actually synthesizes ATP from ADP + Pi)
- as eletrons flow through channels in Fo conformational changes occur in F1 that lead to the generation of...
- ATP
- for every 4H+ that move through how many ATP molecules are generated?
- 1
- Krebs Cycle
- occurs in the matrix of the mito., generates NADH, FADH2, and some ATP, as well as CO2 as a byproduct
- pyruvate
- starting molecule that enters the Krebs cycle
- for each pyruvate the cycle will generate ?? NADH, ??FADH2, ?? ATP, and the ?? CO2
- 4 NADH, 1 FADH2, 1ATP, and the 3CO2
- For each starting glucose, ?? pyruvate are generated during glycolysis;
- 2
-
per glucose the Krebs cycle generates:
⬢ 6CO2 as byproducts
⬢ 8 NADH = 24 ATP equivalents
⬢ 2 FADH2 = 4 ATP
⬢ 2 ATP are drectly produced - for a total yield 30 ATP equivalents from the Krebs cycle
- Glycolysis
- splitting of glucose into two three carbon molecules with the release of energy; occurs in the cytosol and the endproduct (pyruvate is transported into the mitochondrion); no oxygen is required
- glucose is split into two glyceraldehyde 3-phospahte molecules (with several intermediate molecules and each step catalyzed by enzymes)
- note that included in these reactions is the addition of two phospahte groups, so two ATP molecules are consumed in these initial reactons (energy of activation)
- each glyceraldehyde 3-phospahte then has an inorganic phospahte added (no ATP consumed);
- this addition is highly exergonic and is coupled to the reduction of NAD+; the product of this step is 1,3 bisphosphoglycerate
- each 3 phosphoglycerate is converted to pyruvate and a single molecule of ATP is produced via substrate level phosphorylation
- each 1,3 bisphosphoglycerate is then dephopsphorylated in substrate level phosphorylation to produce a molecule of ATP; the product is 3 phosphoglygerate
- Summary - Products and byproducts
-
A. Gylcolysis - 2 NADH + 2 ATP
B. Krebs Cycle - 8 NADH + 2FADH2 + + 2ATP + 6CO2
C. Oxidative Phosphorylation - 34 ATP + 12 H2O (O2 consumed)
D. C6H12O6 + 6O2 -------> 38 ATP + 6CO2 + 6H2O - Cellular Respiration and Physiological Conditios (with respect to O2)
- Pyruvate is a key intermediate.
- Cellular Respiration and Physiological Conditions (with respect to O2)
- Pyruvate is a key intermediate.
- Photosynthesis
-
the generation of carbohydrate using light energy:
Requires carbon dioxide and water as reactants - Byproducts are oxygen and water - Photosynthesis Summary Equation
- 6CO2 + 12H2O -----> C6H12O6 + 6O2 + 6H2O
- the ????? of CO2 is incorporated into carbohydrate using high energy molecules produced using sunlight energy
- carbon
- what drives an electron trnsport chain that is used to make these high energy molecules?
- sunlight
- what comes from the water moleule (splitting of water)?
- oxygen
- what are the primary photosynthetic organs of plants?
- leaves
- what are the organelles within which photosynthesis occurs?
- cholorplasts
- chloroplasts contain chlorophyll which is...
- a pigment which is capable of absorbing sunlight energy
- there are HOW MANY types of chlorophyll molecules?
- 3 : each having slightly different absorption characteristics
- (most land plants have ....
- both chl. a and b
- chlorophyll molecules are organized into photosystems on the
- thylakoid membranes
- the photosystem consists of
- antennae chlorophyll molecules, a rection center chlorophyll, and associated proteins
- WHAT is transferred from the antennae chlorophyll molecules to the reaction center chlorophyll where WHAT begins?
- light energy - electron transport
- Light Reactions
-
1. require light
2. occur on the surface of the thylakoids
3. generate ATP and NADPH
4. require H2O and release O2 as a by product
5. involves a electron trnsport chain similar to that of cellular respiration - The light reactions involve the coordinated action of two WHAT?
- photosystems: PS 1 AND PS 2
- cyclic electron flow
- produces nearly equal quanties of ATP and NADPH as well as consumes H2O and produces O2 as a by product
- noncyclic electron flow
- (from Fd of PSI to Cyt C of PSII) produces ATP only
- PSII
-
1. has the OEC and thus consumes H2O and liberates O2
2. generates the protomotive force (ATP synthesis) - PSI
- 1. receives e- from PSII and produces NADPH
- The Calvin Cycle
-
(light independent reactions)
1. can occur in either the light or dark
2. uses the high energy molecules produced in the light reactions to make carbohydrate -
Cell Wall (Plant Cells)
Function - protection, maintains cell shape, support
- Cell Wall Structure
- 1. the cell wall of higher plants is composed of numerous overlapping cellulose fibers
- Primary Type of Cell Wall
- thin and pliable, and allows for growth of the cell; produced first as the cell matures
- Secondary Cell Wall
- much more rigid and thicker than primary cell wall; produced after the primary wall
- Plasma Membrane Function
-
1. regulates the passage of substances into and out of the cell
2. is selectively permeable
: certain small molecules will diffuse across the PM (O2, CO2, H2O): - Plasma Membrane Structure
-
1. is fundamentally a phospholipid bilayer that contains some associated protein
2. the membrane is structurally dynamic (the functional membrane is somewhat like a fluid or gel) -
Movement Across Membranes:
diffusion - spontaneous movement of molecules down a concentration gradient
-
Movement Across Membranes:
osmosis -
diffusion of water across the membrane
 unlike solute, water moves from hypotonic to hypertonic solutions - facilitated diffusion
-
protein assisted
 allows larger as well polar molecules to cross the PM down a concentration gradient - diffusion, fac. diffusion, and osmosis are...
- passive processes (passive transport)
- Active transport
- requires energy (ATP) and proteins in order to occur; substances are moved against their concentration gradient
- Nucleus
-
The largest and most conspicuous organelle
B. Enclosed by a double membrane that comprises the nuclear envelope - Nucleus' Nuclear Envelope
- has pores that regulated the movement of molecules into and out of the nucleus
- The nucleus contains most of the cell’s DNA in the form of chromatin
- chromatin = DNA + bound protein
- Ribosomes
-
. Site of protein synthesis
B. May occur freely or bound to membranes of the ER - Endomembrane System
-
an integrated set of membranes within the eukaryotic cell (integrated = they work together to accomplish certain functions and, in some cases, are physically joined
:these membranes are “integrated†in that they are physically joined or communicate through vesicles: - vesicle
- a “packet “of substances that are surrounded by a membrane
- Endomembrane System consists of...
- consists of the nuclear membrane, endoplasmic reticulum, golgi apparatus, lysosomes, and vacuoles
- Endoplasmic Reticulum (ER)
- A. A complex of membranes folded into sac-like structures that are joined with the nuclear membrane
-
2 Types of ER:
Smooth
Rough -
Smooth - no bound ribosomes
Rough - has bound ribosomes - Functions of the ER
-
 Synthesis of phospholipids (Smooth ER)
 Breakdown of drugs and other toxic substances
 Manufacture of proteins that will be secreted outside the cell or deposited in the plasma membrane - Golgi Apparatus (GA)
- Made of flattened sacs (cisternae) that modifies, stores, and routes products from the ER
- Functions of the GA
-
chemical modification of proteins and phospholipids synthesized in the ER
⬢ directs proteins, phospholipids, and other molecules to other places in the cell - Lysosomes
-
A membrane enclosed bag of hydrolytic (digestive) enzymes
- enzymes within lysosomes are capable of digesting almost any kind of molecule - Functions of Lysosomes
-
intracellular digestion
⬢ recycling of macromolecules within the cell
⬢ programmed cell destruction - Vacuoles (Plants)
- A compartment (usually large) that is membrane bound
- Vacuoles function in:
-
storing food (formed by phagocytosis)
2. pumps (contractile vacuoles)
 storage (central vacuoles of plants) - Mitochondria
-
-"powerhouse" of the cell (site of ATP production)
Organic molecule + oxygen = CO2 + H2O + ATP + Heat - Chloroplast
-
site of photosynthesis:
Light + CO2 + H2O = carbohydrate + oxygen - Cytoskeleton
- a network of fibers that forms a framework for support, provides a means for movement, and enables a cell to maintain and change shape
- Peroxisomes
-
. organelles that contain enzymes that metabolize oxygen and peroxide
B. additional functions include:
- breakdown of fatty acids
- detoxification of alcohol and other toxic substances - Hypertonic Solution:
-
Solute concentration higher than cell
More dissolved particles outside of cell than inside of cell
Hyper = more (think hyperactive); Tonic = dissolved particles
Water moves out of cell into solution
Cell shrinks - Hypotonic Solution:
-
Solute concentration lower than cell
Less dissolved particles outside of cell than inside of cell
Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles
Water moves into cell from solution
Cell expands (and may burst) - Solute
- dissolved particle
- Solvent
- liquid medium in which particles may be dissolved