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