Composition and Structure of Cell Membranes Flashcards
Eukaryotic cell
Has a nucleus
Prokaryotic cell
Has no nucleus
Micelle
Agrregated phospholiped, formed sponaneously requires no energy, important for absorption of fat soluble vitamins and complex lipids
4 Factors affecting fluidity
- # of carbons in a hydrocarbon chain (Typically 16-18, longer chains are less fluid and tightly packed)
- Double bonds in hydrocarbon chains (produces bends in chain, unsaturated, more fluid)
- Temperature (High temp=High fluidity, more thermodynamic energy and movement)
- Cholesterol (Maintains fluidity at various temperatures)
What function does cholesterol serve to the membrane
-Maintains ideal fluidity and structure at various temperatures
-Makes up 50% of molecules found in membrane
-More cholesterol in saturated areas
Factors affecting permeability
-A less fluid membrane is less permeable
-Hydrophobic molecules pass quickly
-Small molecules pass quickly
-Non-polar molecules pass quickly
-Large or charged molecules require protein channels
How are hydrophilic molecules transported?
By proteins embedded in the cell membrane (protein channels)
Passive diffusion
small molecules move from high to low concentration in and out of cell
Passive transport
uses no energy but does require membrane embedded proteins
Active transport
Moves molecules against the concentration gradient and involves embedded proteins requiring ATP
What are 2 ways water can move across the membrane?
-Slowly by osmosis
-Quickly using aquaporin transmembrane proteins
Primary active transport
ATP hydrolysis affects transmembrane proteins, causing a conformational change to pump a substance (ex. Na-K pump)
Secondary active transport
Nearby protein channels take advantage of eldectrochemical gradients established by primary active transport to move their own solutes
Na-K pump
-Pumps 3 Na out and 2 K in
-Goes against concentration gradient
-Protein shape is changed by ATP and allows Na-K exchange
Eukaryote cell structure
External and internal membrane network, double membrane bound nucleus, many organelles
Prokaryote cell structure
External membrane, no nucleus (nucleoid), few organelles
Chloroplast function and structure
-Goes through photosynthesis to produce sugars
-Has a double membrane
-Contains thylakoids containing pigments and enzymes for photosynthesis
Mitochondria structure and function
-Processes sugars to obtain ATP
-Outer and inner membrane
-Inner membrane is connected to sack-like structures called cristae where ATP is synthesized (ETC)
Where did chloroplasts and mitochondria come from?
Prokaryotic cells may have been consumed/entered a host cell and developed a symbiootic relationship
Bacteria supplied energy to host, host provided protection and carbon compounds
Living examples of symbiotic relationships
-Algae and photosynthetic bacteria
-Corals and photosynthetic dinoflagellates
-Sea slugs consume algae to harvest chloroplasts for its own cells
How are fluidity and permeability related
-Not the same but are related
-Proportional (Less fluid=less permeable, more fluid=more permeable)
What are saturated areas in the membrane and what do they look like
-Less fluid and permeable
-Lipid rafts
-High in cholesterol
-Straight, saturated, tightly packed fatty acid tails
Do all cell membranes have the same fluidity?
-NO
-Using FRAP, it was proven molecules making up the nucleus do not move around, but they do in the endoplasmic reticulum
In what order do cells break down macromolecules for energy and when
Carbs, lipids, protein
Carbs are used up first in 15 minutes
Lipids are broken down after carbs are used up and make much more ATP through beta oxidation
Proteins are a last resort
How do camels tolerate their environment
-Humps are fat reserves
-Energy and water are produced from fat reserves by beta oxidation
-Nostrils condense water
-Feces contain very little water
-Camels can tolerate losing 30-40% of their body water
How do geese manage energy for migration
-Geese eat up to 12 hrs a day before migration
-Fat cells are released into the blood stream to be broken down by mitochondria in myocytes for ATP
How do bar headed geese survive low O2 environments
-Can fly as high as mt. everest
-Large lungs, more surface area for O2 intake
-Better breathing patterns
-More cappillaries and mitochondria
