Membrane Transport - Metabolism and Enzymes

Passive Transport

No energy needed

types of Passive Transport

Diffusion

Osmosis

Facilitated Diffusion

Passive goes…

Down the Concentration Gradient (High to Low)

Active Transport 

Energy is needed 

Types of Active Transport

Protein Pumps/Protein Transporter

Exocytosis

Endocytosis

Active goes…

Against the concentration gradient (Low to High)

Diffusion

Molecules spread out evenly into available space, substances diffuse down their conc gradient, no energy needed

Dynamic Equilibrium

Molecules cross the membrane in one direction as the other

Osmosis

Diffusion of water across a selectively permeable membrane, water diffuses from lower solute concentration (high water concentration) to a higher solute concentration (low water concentration) until both equal  

Tonicity

ability of surrounding solute to cause a cell to gain/lose water

Isotonic Solution

Solute concentration is same as inside of cell, no net movement of water

Hypertonic Solution

Cell loses water, solute concentration greater outside of cell

Hypotonic

Cell gains water, solute concentration less than inside

Osmoregulation 

Control of solute concentrations and water balance 

Facilitated Diffusion

Polar molecules and ions unable to cross membrane but can with help of transport proteins

Chanel Proteins

provides corridors that allow specific molecules or ions to cross the membrane

Aquaporins

facilitated diffusion of water

Gated Channels 

Open or close in response to stimulus, which should be electrical

Uniport

Transport of a single type of molecule

Symport

two diff substances move in same direction

Antiport

One substance moved in one direction, while another in different

Active Transport allows…

Cells to maintain concentration gradients 

Co-transport

occurs when active transport of a solute indirectly drives transport of other solutes

• Usually in plants 

Exocytosis and Endocytosis 

used to move larger substances across plasma membrane 

Small

Enter/leave cell through lipid bilayer via transport proteins

Large

Cross membrane in bulk via vesicles

Bulk Transport

Requires a lot of energy because large substances

Exocytosis

Movement out of cell using vesicle

Endocytosis

movement into the cell using vesicles

Exocytosis substances…

engulfed by formation of vesicles around them and many secretory cells use to export products

Exocytosis synapse

• Vesicles containing neurotransmitter arrive at cell membrane

• Ca2+ ions trigger fusion of vesicle into membrane

• Neurotransmitter leaves cell

Endocytosis…

Cell takes macromolecules by forming vesicles from plasma membranes

Types of endocytosis

Phagocytosis

Pinocytosis

Receptor-Mediated Endocytosis 

Phagocytosis 

large particles, cleans up cellular debris 

Pinocytosis

liquids and small particles captured in vesicles formed by infolding of cell membrane

Receptor Mediated Endocytosis

vesicles coated with receptor that recognize spcific ligands for endocytosis

Metabolism

All living organisms extract energy from environment to power functions

Heterotrophs 

• (consumers)- consume organisms for energy

Autotrophs

•  (producers)- light energy into chemical 

Metabolic Pathway

series of defined steps which a molecule is converted to another molecule

If bonds are broken in a chemical reaction…

Potential energy can be released

During energy transfer, some energy is unusable as it is lost as…

Heat

Catabolic

breaking down molecules, releasing some potential energy (Celllar Respiration)

Anabolic 

building molecules, consuming energy 

Gibbs Free Energy

Energy can be used by a system to perform work when temp and pressure are uniform

Greater Free Energy to Lower Free Energy

Negative Value, Exergonic Reactions, energy is release

Lower Free Energy to Greater Free Energy

Positive Value, Endergonic Reactions, energy is taken in

Enzymes are…

catalysts (speed up reactions)

Enzymes ___ activation energy required for a reaction

LOWER

Chemical reactions do not permanently change

Enzymes chemistry or conformation

Enzymes are not used up…

they are reused

Substrate Specificity

recognizes and binds to a specific substrate

Factors affecting enzyme activity 

Temp

pH

Substrate Concentration

Competitive Inhibition

Same structure as substrate, binds and blocks active site so that substrate cannot bind

Allosteric Inhibition

binds to allosteric sites separate from active site and changes conformation of enzyme so that substrate

ATP

Energy Molecule, made up of nitrogenous base, sugar, 3 phosphate groups

Energy Recoupling

Transfer of energy from one chemical reaction to another

ATP MuST BE….

Regenerated constantly

Advantages of ATP

• easy to use

• regenerate quickly 

• utility