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Bio 160

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Bio 160 Unit 2 1 Week Two- Lecture One – PowerPoint PPT presentation

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Title: Bio 160


1
Bio 160
  • Unit 2 1
  • Week Two- Lecture One

2
Cellular Functions
  • Thermodynamics and energy
  • is the capacity to do work
  • Kinetic - actual work
  • Potential - stored work
  • Heat - given off from the movement of
    molecules
  • Chemical - stored for cells

3
  • Thermodynamic laws- energy transformations
  • 1st law- energy can neither be created nor
    destroyed, but it may change form
  • 2nd law- law of entropy- energy transformation
    results in chaos of randomness. (entropy)
  • Implication for the 1st law
  • Energy that comes to us from the sun can be
    transferred into many different forms through
    different systems

4
  • Implications for the 2nd law
  • As one environment becomes more organized, all
    around it becomes disorganized
  • Disorganized energy is heat
  • A cell creates an ordered space, increasing the
    entropy around it, so it can not be transfer or
    transform energy 100 efficiently, therefore
    energy can not be transferred 100 through a
    system. Most is given off as heat

5
  • Chemical reactions store or release energy
  • Endergonic reactions require energy to be put
    into the system, then stores energy in the
    chemical products. (ex. Photosynthesis)
  • Exergonic reactions release energy out of the
    system from energy rich bonds being broken in the
    reactants. (ex. Cellular respiration)

6
  • Cellular Metabolism- all of the endergonic and
    exergonic reactions of a cell
  • ATP- adenosine triphosphate powers nearly all
    forms of cellular work
  • Obtained from food molecules
  • Energy coupling reactions for cellular
    metabolisms are run by ATP
  • ATP is a little unstable, so it can be broken
    down to ADP through hydrolysis
  • A phosphate is removed, releasing energy
    (dephosphorylation)

7
  • Exergonic reaction
  • Phosphorylation- ADP receives a phosphate
    converting it to ATP, energizing it to perform
    work
  • Dephosphorylated ATP is converted to ADP
    adenosine diphosphate by the removal of a
    phosphate, releasing energy for the cell to do
    work.
  • During cell respiration ADP is phosphorylated
    through dehydration synthesis and converted back
    to ATP. Therefore it is renewable source.

8
  • Enzymes control the rate of chemical reactions
    without being consumed or changed in any way.
    (Biological catalyst protein)
  • Works by lowering the energy barrier or the
    energy of activation energy needed to start a
    reaction
  • The enzyme has no effect on the amount of energy
    content of reactants or products, just on the
    rate of the reaction.
  • Enzymes are very specific in where they work
  • Use a lock and key mechanism. The active site
    on the enzyme must have the appropriate fit
    with receptor site on the protein substrate

9
  • Enzymes require a specific environment to
    function optimally. (Temp, pH, salinity, etc.)
  • Some enzymes also require a non-protein cofactor
    or coenzyme (organic molecule) to function
    properly.
  • Enzymes may be blocked from their substrates by
    inhibitor chemicals
  • Competitive inhibitor- competes with the enzymes
    normal substrate, tying up the enzyme
  • Non Competitive inhibitor- binds to the enzyme
    outside of the active site, changing the shape of
    the enzyme, preventing the enzyme from fitting
    with its own substrate
  • Inhibitors regulate cell reaction rates by
    slowing it down
  • Negative feedback regulation of metabolism

10
Cellular Membranes
  • Cellular Membranes control cellular metabolic
    functioning
  • Phospholipid bilayer made of a mosaic of
    different small fragments that can move laterally
    in the membrane
  • Membranes are selectively permeable, allowing
    certain substances in and out, but not others.
  • Types of movement across cell membranes
  • Passive Mechanisms allow movement without the use
    of energy

11
  • Diffusion- molecules moving from areas of ? to
    ? through random molecular motion
  • Passive Transport- diffusion of a substance
    across a membrane along a gradient until
    equilibrium is reached
  • Osmosis- diffusion of water molecules across a
    selectively permeable membrane
  • When water molecules can move across a membrane
    but the solute cannot, different concentrations
    of solutes may result
  • Hypertonic- a solution with a higher of
    solutes in it that the surrounding solution is
    considered to by hypertonic it its solution

12
  • Hypotonic- A solution with a lower of solutes
    in it than the surrounding solution is said to be
    hypotonic to its solution
  • Isotonic- the of solute is the same on both
    sides of the membrane
  • In all of the solutions, water will cross the
    s.p. membrane to reach equal concentrations. The
    direction of osmosis is determined only by the
    difference in total solute .
  • Water balance is controlled by osmoregulation
  • Facilitated diffusion- a special protein embedded
    in the cell membrane called a transport protein
    regulates the diffusion of larger molecules down
    their gradients, thereby facilitating the
    diffusion

13
  • Active transport mechanisms require cell energy
    to move substances across the membrane. Uses ATP
    phosphorylation to activate transport protein
  • Exocytosis- cellular expulsion of molecules using
    cellular energy
  • Endocytosis- cellular intake of macromolecules
    using cellular energy
  • pinocytosis-cellular intake of fluid droplets
  • phagocytosis- engulfing of large particles from
    outside the cellular membrane
  • receptor- mediated endocytosis- engulfing of
    specific molecules through the use of receptor
    proteins

14
Cellular Respiration
  • The process of creating ATP the organism needs by
    using the materials the body takes in
  • Overall process

15
  • Cells only use 40 of energy released from
    glucose. Other 60 lost as heat
  • During the chemical conversion process of the
    reaction, e- are released from one set of
    molecules and are attached to others, giving off
    energy in the process
  • Accomplished by H atoms moving places (fig. 6.4)
  • H carried by NAD (nicotinamide adenine
    dinucleotide) through an oxidation-reduction
    (redox) reaction
  • 2 hydrogens and 2 e-s are first peeled off of a
    glucose molecule in an oxidation reaction (loss
    of e-)

16
  • The H and 2 e- are shuttled through the oxidation
    by NAD coenzymes and dehydrogenase enzyme
  • NAD becomes reduced, picking up H and 2 e-
    becoming NADH. The other H goes into the fluid
    surrounding the cell
  • The energy from the redox reaction is released
    when NADH releases its e- carriers to become NAD
    again
  • the NADH stores the energy for the cell
  • The e- carriers fall down a series of energy
    level carriers like a stair step
  • Called electron transport chain (e- dance)
  • The e- carrier proteins (levels) are imbedded in
    mitochondrial membranes of the cristae

17
  • 2 mechanisms to generate ATP
  • Chemiosmosis- uses concentration gradients and
    ATP synthatase proteins found in membranes to
    generate most of their ATP
  • Substrate level phosporylation- without a
    membrane, transfers a phosphate group from an
    organic molecule to ADP, happens in the
    conversion of glucose to CO2 in the Krebs cycle

18
  • 3 stages of Cell Respiration (fig. 6.8)
  • Glycolysis- splitting of sugar anaerobically
  • Occurs in cytoplasm without oxygen needed\
  • Oxidizes glucose into pyruvic acid through 9
    chemical steps
  • 2 separate stages of glycolysis
  • First stages are preparatory and consume energy
  • ATP is used to split one glucose into 2 smaller
    sugars that are primed to release energy
  • Since the prep phase uses 2 ATP, only 2 ATP are
    the end product generated by glycolysis
  • Produced through substrate- level
    phosphorylation
  • 2 molecules of NAD are reduced to NADH
  • 2 ATP are available for immediate use by the cell
  • NADH must enter electron transport system for E
    to be released
  • Must have O2 to release E

19
  • Second stages release energy
  • Happens in tandem
  • NADH is produced when a sugar molecule is
    oxidized and 4 ATP are generated

20
  • Total end products of glysolysis
  • 2 ATP Heat 2 pyruvic acid
  • Krebs Cycle- aerobic respiration
  • Pyruvic acid must be groomed to enter the Krebs
    Cycle
  • It is oxidized while a molecule of NAD is
    reduced to NADH
  • A C atom is removed and released in CO2
  • Coenzyme A joins with what is remaining of the
    pyruvic acid to form AcetylCoenzyme A
  • The acetyl part then enters the krebs cycle, the
    coenzyme A splits off and is recycled

21
  • Krebs cycle happens in the cristae of the
    mitochondria
  • Acetyl fragment combines with the oxaloacetic
    acid already in the mitochondria
  • This forms citric acid. A molecule of CO2 is
    released and NAD is reduced to NADH, which
    releases an e- to the electron transport system
  • Citric acid is converted to alpha- ketoglutaric
    acid, phosphorylated to produce ATP and NAD is
    reduced to NADH, again releasing an e- to the
    electron dance. Four-carbon succinic acid results.

22
  • At succinic acid, enzymes rearrange chemical
    bonds FAD, a related hydrogen carrier similar to
    NAD, is reduced to FADH, releasing more e- to the
    electron dance. Malic acid is formed (FAD flavin
    adenine dinucleotide)
  • At malic acid NAD is reduced to NADH and a H
    ion, adding more e- to the dance. Malic acid is
    converted to oxaloacetic acid, which is ready to
    accept a new acetyl group for another turn at the
    cycle
  • End products of Krebs 36 ATP CO2 HEAT
  • 2 ATP are from substrate- level phophorylation

23
  • Approx 34 ATP are formed by chemiosmotic
    phosphorylation
  • The electron transport chains are built into the
    convoluted cristae of the mitochondria, there are
    many sites for the electron dance to occur
  • Electron transport system is third stage of
    cellular respiration
  • Pathways for dietary carbohydrates, lipids and
    proteins
  • Carbohydrates break down into sugars that
    eventually break down into glucose and then goes
    into glycolysis
  • Quick access energy

24
  • Lipids are broken down through hydrolysis into
    fatty acids and glycerol
  • Fatty acids may be stored as fat, be converted
    into ketone bodies (acetone) and further broken
    down to enter the Krebs or eliminated, or
    undergo beta- oxidation and be converted straight
    into Acetyl Co A
  • Glycerol may be converted into Acetyl Co A and
    enter the Krebs or be converted to glucose and
    undergo glycolysis
  • Yields high energy when used but likes to be
    stored rather than used
  • 2x as much ATP as in the same amount of starch

25
  • Proteins undergo hydrolysis to break into amino
    acids that are then broken into deaminated
    portions which can go to fat, glucose, and acetyl
    Co A to enter glycolysis/Krebs cycles. The other
    portion of the amino acid is the NH2 (Ammonia)
    group, which is excreted through urea
  • Long term energy- takes long time to digest
  • Food Molecules are used for other stuff besides
    Krebs Cycle
  • Used for biosynthesis (uses ATP to do so)
  • Produces proteins, lipids, and polysaccharides
  • Used for growth and repair
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