C5 cellular respiration Flashcards
(28 cards)
Why can some things pass through a cell membrane whereas others can’t
- Plasma membrane are selectively permeable
- Transport can be active/passive
- Water soluble substances requires specialised transmembrane proteins to function as channels or carriers
Permeability
- Solubility in lipids
- Driving forces (gradients)
- Molecular size
How do ions & molecules pass through the cell membrane
3 Passive transports
1. Diffusion through the lipid bilayer (lipid soluble substances)
2. Diffusion through ion channels (water soluble substances)
3. Facilitated diffusion using a carrier (water soluble substances)
Active transport- requires ATP
Diffusion through the lipid bilayer
Lipid soluble substances (lipids, respiratory gases, small alcohols, urea)
- driven by a concentration gradient
Diffusion across the lipid bilayer
Water soluble substances (ions, small sugars, amino acids, water)
- needs integral membrane proteins to move across the cell
1. Small ion & water -> channels
2. Sugar & a.a. -> facilitated diffusion
- driven by concentration/electrical gradient
Facilitated diffusion
Solute binds to a specific transporter on one side of the membrane, released on the other side
- Glucose out of cell, fructose into cell
Rate of facilitated diffusion depends on
Steepness of concentration gradient
Number of transporter proteins in membrane (transport maximum)
Gated protein channels
ion channels - selective & specific
- driven by electrochemical gradient
- some channels continuously open, some open transiently
- transport faster than facilitated diffusion
Active transport
Energy-requiring process- moves solutes against a concentration gradient
Primary active transport
energy derived directly from ATP
- metabolic (ATP hydrolysis)
Secondary active transport
energy derived indirectly from ATP
- cotransport of Na+/H+
Purpose of primary active transport
- maintain active transport of Na+ & high conc of K+ in cytosol
- operates continually
Purpose of secondary active transport
energy stored in Na+/H+ conc gradients used to drive other substances against their own concentration gradient
- Plasma membrane contains several antiporters & symporters powered by sodium ion gradient
why does water move from one place to another within the body
- Diffusion through lipid bilayer/aquaporins
- Osmosis: movement of water from a low solute conc. to a high solute conc. across a semi-permeable membrane
What is ATP
Molecule for temporary energy storage
- 3 phosphate groups attached to an adenine base & a 5C sugar (ribose)
Why do we need ATP
- muscle contraction
- active transport
- movement of structures within cells
How is glucose used to produce energy within the cells
Glycolysis
Glycolysis processes
- sugar activation
- Sugar cleavage
- oxidation & ATP formation
Final products
- 2 pyruvic acid
-2 reduced NAD+
- net gain of 2 ATP molecules
After glycolysis, if oxygen is available
prepares to enter Krebs cycle
After glycolysis, if oxygen is not available
pyruvic acid accepts H2 from NADH2-> formation of lactic acid
- sugar activation
2 ATPs used to activate glucose
- sugar cleavage
6C sugars splits into 2 3C sugars
- each 3C sugar has a phosphate group
- Oxidation of ATP formation
- phosphates split from the sugar & captured by ADP to form 4 ATP molecules
- 3C sugar: pyruvic acid
Acetyl Coenzyme A
Pyruvic acis enters mitochondria -> decarboxylation
- pyruvate dehydrogenase converts 3C pyruvic acid into 2C acetyl group + CO2
2 acetyl group attached to coenzyme A-> acetyl coenzyme A -> enters krebs cycle
Coenzyme A derived from Vit.B
Carrier for 2C acetyl group
