Cell Biology Chapter 10 - Cellular Metabolism and Energy Storage Flashcards
Energy Exists In Three Forms
Kinetic Energy
Potential Energy
Heat Energy
1st Law of Thermodynamics
Energy can neither be created nor destroyed
2nd Lab of Thermodynamics
Energy systems have a tendency to increase their entropy
Long-term Energy Storage In Cells
Fats And Polysaccharides
Are polymers composed of small, repeating structures
Highly organized and spontaneously form hydrophobic lipid droplets
Have less entropy (are more ordered) than poly/oligosaccharides, therefore they carry more useful energy
Of Short-term Potential Energy
High-energy Electrons And Ion Gradients
Ion Gradients
Created by a concentration imbalance across a membrane
[Na2+]out is 148 mM versus [Na2+]in is 10 mM
[K+]out is 5 mM versus [K+]in is 148 mM
Chloroplasts and Mitochondria use a proton gradient
Cells Couple Energetically Favorable and Unfavorable Reactions to Facilitate Unfavorable Reactions
Baws!
Electrical Potential
The Amount of a Potential Energy Stored in an Ion Gradient Can be Expressed as an Electrical Potential
Electrical Potential is expressed in volts
Difference in electrical potential between two points is called voltage
Electrochemical potential exists when BOTH an electrical imbalance AND a chemical imbalance exists
Membrane transport proteins
are responsible for moving ions through the phosopholipid bilayer of cellular membranes.
Organized into three groups: channels, carriers, and pumps.
Protein channels
dissipate gradients
Have pores
Have a selectivity filter
Alpha helices in transmembrane segments
Facilitated Diffusion
through a channel and down a concentration gradient
Open and close (gated)
Regulated
Sensitive to post-translational modification
opposite of Facilitated Diffusion
Simple Diffusion – passage of molecules through the plasma membrane unassisted
Ligand-gated
Logands attach —-> gates open
Voltage-gated
threshhold reaches -60 -70
Voltage gated shapes
- sliding helix
- Paddles
- Transporter like
Stretch-gated or Stretch-activated
Found in nerve cells that are sensitive to physical deformation of their plasma membranes
Touch
Hair cells in inner ear
Some pain receptors
Passive Carrier Proteins Dissipate Gradients
- dont form pores
conformation change in a carrier protein
- Attaches to channel by active site
- Channel changes shape. Open end becomes closed end and vice versa. attached content is spewed in.
Uniport
refers to the transport of a single ligand by a carrier in either direction
Symport
simultaneous transport of two ligands by a single carrier in the SAME direction
Antiport
simultaneous transport of two ligands by a single carrier in the OPPOSITE direction across a membrane. eg Na+ & H+
Energy-coupled Carrier Proteins (Pumps) Build Gradients
Direct active transport &
Indirect active transport (One gradient supplies the energy to build another)