Cellular Functioning

1
Cellular Functioning

• Chapter 5

2
Cellular Membranes
3
Plasma Membranes Role

• Genes not necessary to arrange
• Structure function similar in all life
• Physical isolation
• Ions nutrient enter, wastes secretions exit
• Allows a concentration gradient to develop
• Regulates exchange with environment
• Maintains homeostasis
• Selective permeability
• Polarity (hydrophobic vs. hydrophilic)
• Charge (charged vs. uncharged)
• Size (large vs. small)

4
The Fluid Mosaic Model

• Integral protein
• Channels
• Carriers
• Peripheral protein
• Phospholipids
• Bilayer
• Hydrophilic
• Hydrophobic
• Fluidity
• Cholesterol
• Temperature
• Cell cell recognition

5
Types of Transport

• Active

• Passive

• Energy not required
• Movement down a concentration gradient
• Specific types
• Diffusion
• Osmosis
• Maintains dynamic equilibrium

• Energy required
• Movement against a concentration gradient
• Maintains disequilibrium

6
Reviewing Terms

• Solute
• Solvent
• Solution
• Concentration

7
Simple Diffusion

• Movement of MOLECULES down their concentration
  gradient
• Small, nonpolar molecules
• E.g. O2 in and CO2 out in red blood cells
• Each substance is independent
• Continues until equilibrium no NET movement

8
Facilitated Diffusion

• Transport proteins move MOLECULES down their
  concentration gradient
• Large, polar molecules
• E.g sugars, AAs, ions, and water
• Are specific to substances
• Channels can opens or close carriers change
  shape
• Rate increases with an increase in proteins

9
Osmosis

• Movement of WATER down its concentration
  gradient
• Water binds to solute in solution
• More solute less free water less water
  available to move
• Depends on TOTAL solute concentration and
  permeability has a role too

water molecules
glucose molecules
10
Tonicity

• Ability of a solution to cause a cell to gain or
  lose water
• Depends on solutes that cant cross PM relative
  to that in the cell
• Hypotonic solutions have a ___?__ solute than
  the cell
• Water moves in
• Animal lyse
• Plant turgor pressure (central vacuole)
• Hypertonic solutions have a ___?__ solute than
  the cell
• Water moves out
• Animal crenation
• Plant plasmolysis
• Isotonic solutions have ___?__ solute as the
  cell
• Water shows no NET movement
• Plant flaccid

11
Cellular Effects
12
Active Transport

• Movement of MOLECULES against their concentration
  gradient
• ATP is energy source
• Maintains disequilibrium

13
Applying These Concepts

• Diffusion overview
• Practice problem
• Impermeable to sucrose
• Movement of solutes?
• Movement of water?
• Solution type?
• Resulting cell shape?

14
Osmoregulation

• Control of water balance
• Paramecium use contractile vacuole
• Excess water out so cell doesnt lyse
• Plants use central vacuole

15
Other Active Transport Types

• Exocytosis removes from inside the cell
• Golgi apparatus to PM
• Endocytosis brings into the cell
• PM pinches in to form vesicles
• 3 types
• Phagocytosis
• Pinocytosis
• Receptor-mediated

16
Energy Reactions
17
Energy

• Capacity to cause change or rearrange matter
• KE energy of movement or objects in motion
• Heat random movement of particles associated
  with KE
• PE stored energy as a result of structure or
  location
• Chemical energy PE available for release, to do
  work
• Cells transform chemical energy into usable energy

18
Chemical Reactions

• Exergonic release energy
• Reactants have more PE than products
• Cellular respiration converts stored energy to
  usable form
• Endergonic needs net input of energy
• Products have greater PE than reactants
• Photosynthesis converts energy-poor reactants to
  energy rich sugars
• Amount of energy is equal to the difference in PE

19
What is ATP?

• Adenine triphosphate (nucleotide)
• Powers all cellular work
• ATP H2O ADP E phosphate
• Reversible because phosphate can rejoin ADP
• Phosphorylation phosphate joins another
  molecule to energize it

20
Enzymes

• Proteins that increase the rate of reaction w/o
  being consumed
• End in -ase and are named for substrates
• Lower the EA barrier
• Energy of activation (EA) energy needed to be
  overcome to start a reaction
• Net change of energy is the same with or without

21
Enzymatic Reactions

• 3D shape determines reactivity of enzyme
• Synthetic or degradative
• Enzyme activity factors
• Temperature and pH denature
• Buffers help regulate
• Cofactors/coenzymes are nonprotein helpers
• Concentrations

22
Enzyme Inhibitors

• Competitive
• Resembles substrate and
• competes for binding
• Increasing substrate can
• compensate
• Noncompetitive
• Binds elsewhere than active site
• Causes conformational change so cant bind
  substrate
• Feedback inhibition prevents overproduction of a
  substance by the cell
• Regulates metabolism