Flashcards in Lecture 6- Body Water And Cell Membranes Deck (17):
Define the major compartments of body water
Water makes up 60% of total body weight
-66% of TBW is the intracellular fluid (fluid inside cells)
-33% of total body water is in the extracellular fluid (fluid outside cells)
20% of above is plasma in the ECF
80% of extracellular fluid is in the interstitial fluid ECF outside the blood. Refer to slide 12 of PowerPoint
Substances dissolved in liquid are called?
Liquid in which they dissolve are called?
Combination of solutes dissolved in solvents are called?
Water acts as a solvent for the many solutes found in the body
Solutes can be electrolytes or non electrolytes
What is the difference between electrolytes and non-electrolytes?
-dissociate into charged ions in water
-can conduct electricity
-include inorganic salts, inorganic and organic acids and bases, some proteins Na+ Cl-
-don't dissociate in water
-aren't electrically charged
-mostly organic molecules
In an animal electrolytes have more osmotic activity than non-electrolytes because each electrolyte dissociates into at least two ions
How do you work out the osmolarity of a solution
Also why can't you often refer to it as concentration
Osmolarity= total no. Of particle/liters of solution
What is the 4 functions of the cell membrane?
1. Physical isolation
2. Regulation of exchange with environment eg movement of ions, gases and water
3. Communication between cell and environment eg changes in ECF detected by receptors
4. Structural support- maintains cell shape via intracellular proteins (cytoskeleton)
Describe the structure of the cell membrane and draw it
Fluid mosaic model
-thin phospholipid bilayer (7-8nm)
-polar phosphate heads face the outer surfaces of membrane
-non polar tails of lipid face inwards
- other membrane lipids and proteins are inserted partly/completely throughout the membrane (mosaic)
-imbedded elements can move laterally in the membrane-it is a dynamic fluid structure
-there are peripheral and integral proteins
Which out of red blood cells, myelin membrane (nerve cells) or inner mitochondrial membrane has the most protein in their structure, the most lipid in their cell and the most cholesterol in their structure?
Red blood cells have more protein than lipid but have the most cholesterol out of the three.
Nerve cells have the most lipid
Mitochondria have most protein
In general, more metabolically active cells have more protein in their membranes.
What are the major types of membrane proteins and what are their functions?
1. Integral proteins
-tightly bound in phospholipid bilayer
-extended into and through layers
-include membrane channels and transporters
2. Peripheral proteins
-attach loosely to integral proteins or phospholipid head
-can be removed without disrupting membrane integrity
-include enzyme and structural proteins
Membrane proteins main functions are:
1. Transporters: allows molecules that can't diffuse across membrane to enter cell eg kidneys to reabsorb water via aquaporins and glucose
2. Structural components: connects membrane and cytoskeleton to maintain shape of cell
3. Receptors: activate biomechanical pathways in response to binding of chemicals called ligands (transmitters or hormones)
4. Enzymes: catalyst reactions on internal or external surface of the cell
What are glycocalyx cells? What do they function as?
-carbohydrate containing molecules, with branching sugar groups, they form a layer called the glycocalyx on the extracellular membrane surface.
-carbohydrate chains form on either membrane lipids (glycolipids) or integral membrane proteins (glycoproteins)
-the have an important function which is cell recognition ie immune response to bacteria. The pattern of sugars is cell type specific
There is significant structural variation between different regions of the same membrane. Eg lips rafts, explain this.
What is homeoviscous adaptation?
Lipid rafts are thickened regions of membrane containing higher density of cholesterol, glycolipids and integral proteins.
Homeoviscous adaptation means that the lipids in the membrane can change their composition and position which keeps membrane fluidity relatively constant in changing conditions
Explain the clinical applications of liposomes
-new advance in drug delivery
-centre of liposomes filled with drugs, antibodies, or DNA fragments
-liposomes act to reduce toxicity and improve efficacy of drug
-they release the drug in a pulsatile manner
If you have a saline drip put into your arm, which body compartment will saline enter first?
Tissue dehydration involves loss of fluid from which body compartments
The 10% loss of body weight caused a decrease in TBW by 17% from the control value; 41% of this loss was from ICF, 47% from ISF, and 12% from
Answer: interstitial fluid