How do we fuel our body? Flashcards
What is the Plasma Membrane?
- Boundary of cell – encloses and supports cell contents.
- Separates intracellular vs. extracellular materials.
What is the Fluid Mosaic Model?
-Attaches cells to other cells and to the surrounding matrix.
-Cells communicate with their environment through their cell membrane.
-Determines what can move into and out of the cell (selectively permeable).
o Intra- and extracellular environment is different
-Difference in charge across membrane – membrane potential
-Structure – fluid mosaic model
What is the lipid bilayer made of?
- Phospholipids
- Cholesterol
What are proteins in the Fluid Mosaic Model?
- Inserted in the lipid bilayer
- Peripheral or integral
- Many are involved in transporting molecules across the cell membrane, e.g. channel proteins, carrier proteins, ATP powered pumps.
What are channel proteins?
-Form a tiny channel through the plasma membrane
-Molecules of certain size, shape and charge can pass through
-Non-gated ion channels
oAlways open
-Gated ion channels
oOpened or closed by certain stimuli
What are carrier proteins?
-Also called transporters
-Integral proteins move ions from one side of membrane to the other
o Specific binding sites
o Protein changes shape to transport ions or molecules
o Resumes original shape after transport
o Uniporters, symporters, antiporters
What is ATP-Powered transport?
- Requires energy in the form of ATP.
- Transports substances AGAINST their concentration gradient, so the cell can accumulate substances.
- Example we learn is the sodium potassium pump.
What is a Solute?
- Dissolved substance in a solution
- e.g. glucose, sucrose, ions (Na+, K+, Cl-)
What is Solvent?
- Liquid that holds solutes
- Generally, water
What is Solution?
-Mixture formed when solute dissolved in solvent
What is Diffusion?
- Molecules move from an area of higher concentration to an area of lower concentration.
- Continues until the molecules have evenly distributed themselves throughout the solution.
What is Diffusion through the cell membrane?
- Certain specific nonlipid soluble molecules or irons diffuse through membrane channels
- Other non-lipid soluble molecules, for which membrane channels are not present, can’t enter the cell
- Lipid soluble molecules diffuse directly though the plasma membrane
What is Filtered Diffusion?
- Move large, water soluble molecules or electrically charged molecules across the plasma membrane.
- Amino acids and glucose in, manufactured proteins out
- Passive
What is Osmosis?
-Osmosis is the diffusion of water across a selectively permeable membrane, e.g. the plasma membrane
What
- A selectively permeable membrane lets water to pass through, but any solutes dissolved in the water
- If the beaker contains distilled water (water with no solutes), water molecules will move back and forth across the membrane at the same rate
- The water level stays the same on both sides of the membrane
What is the Effect of a Semi-Permeable Membrane?
- Solute added to one side of beaker. It is too big to cross through the pores in the membrane
- Solute distributes itself evenly in one half of the beaker
- Water moves from area of low solute concentration to high solute concentration.
- Water level on the RHS of the beaker drops and on the LHS of the beaker increases.
- Water is moving down its concentration gradient
What is the effect of the concentration of the solution?
- From these two examples we can see that the concentration of the solute determines how much water moves across the membrane
- The more concentrated a solution is, the more that solution will “pull” water towards it.
- A dilute or weak solution with a small number of solutes will only have a weak “pull” on water.
- A concentrated solution with a large number of solutes will have a strong “pull” on water.
What is Osmolarity?
- This “pull” on water created by solutes is termed the solution’s Osmotic pressure or Osmolarity
- Osmolarity is measured in Osmoles/L or mOsmoles/L.
- Generally, in the body fluids we are working with solutions which are fairly dilute and so we use the unit mOsmoles/L.
- As we have seen, the osmolarity of a solution is directly related to the concentration of the solution.
- A weak solution will have a low osmolarity value
- A more concentrated solution will have a higher osmolarity value.
- A solution that has an osmolarity of 100mOsmol/L will have a smaller “pull” on water than a solution which has an osmolarity of 300mOsmol/L.
What is Osmolarity in relation to Body Cells?
-Body fluids have many dissolved solutes
-Body fluids can be divided into
o intracellular
o extracellular (intercellular & intravascular)
-The osmolarity of the intracellular fluid of a normal cell under normal conditions is approximately 290mOsmol/L
What is an Isotonic Solution?
- When a cell is placed in a solution that has the same osmolarity as the inside of the cell, the solution is called isotonic
- Water will move between the intracellular and extracellular fluid at equal rates (no net movement of water) and the cell is happy.
What is a Hypertonic Solution?
- Let’s place a cell in a solution that has a higher osmolarity that inside the cell
- The solution with the higher osmolarity contains a greater concentration of solutes
- The solution is hypertonic
- It exerts a stronger “pull” on water
- Water is literally pulled out of the cell
- The cell loses water and shrinks
What is a Hypotonic Solution?
- Let’s place a cell in a solution that has a lower osmolarity that inside the cell
- A solution with a lower osmolarity contains a lower concentration of solutes
- The solution is hypotonic
- In this case the cell exerts a stronger “pull” on water
- Water is literally pulled into the cell
- The cell takes in water – swell – burst!
What is Metabolism?
-Total of all chemical processes that occur in body
-Metabolism includes
o Catabolism
-Energy-releasing process
-Where large molecules broken down to smaller molecules
o Anabolism
-Energy-requiring process
-Where small molecules joined to form larger molecules
What is Catabolism?
-A large reactant is broken down to form smaller products
o Chemical bonds broken; energy released.
o Energy in carbohydrates, lipids, proteins is used to produce energy which drives anabolic reactions, e.g. active cell membrane transport, muscle contraction, protein synthesis.
