Composition and Structure of Cell Membranes

Question 1

Eukaryotic cell

Answer 1

Has a nucleus

Question 2

Prokaryotic cell

Answer 2

Has no nucleus

Question 3

Micelle

Answer 3

Agrregated phospholiped, formed sponaneously requires no energy, important for absorption of fat soluble vitamins and complex lipids

Question 4

4 Factors affecting fluidity

Answer 4

1. # of carbons in a hydrocarbon chain (Typically 16-18, longer chains are less fluid and tightly packed)
2. Double bonds in hydrocarbon chains (produces bends in chain, unsaturated, more fluid)
3. Temperature (High temp=High fluidity, more thermodynamic energy and movement)
4. Cholesterol (Maintains fluidity at various temperatures)

Question 5

What function does cholesterol serve to the membrane

Answer 5

-Maintains ideal fluidity and structure at various temperatures
-Makes up 50% of molecules found in membrane
-More cholesterol in saturated areas

Question 6

Factors affecting permeability

Answer 6

-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

Question 7

How are hydrophilic molecules transported?

Answer 7

By proteins embedded in the cell membrane (protein channels)

Question 8

Passive diffusion

Answer 8

small molecules move from high to low concentration in and out of cell

Question 9

Passive transport

Answer 9

uses no energy but does require membrane embedded proteins

Question 10

Active transport

Answer 10

Moves molecules against the concentration gradient and involves embedded proteins requiring ATP

Question 11

What are 2 ways water can move across the membrane?

Answer 11

-Slowly by osmosis
-Quickly using aquaporin transmembrane proteins

Question 12

Primary active transport

Answer 12

ATP hydrolysis affects transmembrane proteins, causing a conformational change to pump a substance (ex. Na-K pump)

Question 13

Secondary active transport

Answer 13

Nearby protein channels take advantage of eldectrochemical gradients established by primary active transport to move their own solutes

Question 14

Na-K pump

Answer 14

-Pumps 3 Na out and 2 K in
-Goes against concentration gradient
-Protein shape is changed by ATP and allows Na-K exchange

Question 15

Eukaryote cell structure

Answer 15

External and internal membrane network, double membrane bound nucleus, many organelles

Question 16

Prokaryote cell structure

Answer 16

External membrane, no nucleus (nucleoid), few organelles

Question 17

Chloroplast function and structure

Answer 17

-Goes through photosynthesis to produce sugars
-Has a double membrane
-Contains thylakoids containing pigments and enzymes for photosynthesis

Question 18

Mitochondria structure and function

Answer 18

-Processes sugars to obtain ATP
-Outer and inner membrane
-Inner membrane is connected to sack-like structures called cristae where ATP is synthesized (ETC)

Question 19

Where did chloroplasts and mitochondria come from?

Answer 19

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

Question 20

Living examples of symbiotic relationships

Answer 20

-Algae and photosynthetic bacteria
-Corals and photosynthetic dinoflagellates
-Sea slugs consume algae to harvest chloroplasts for its own cells

Question 21

How are fluidity and permeability related

Answer 21

-Not the same but are related
-Proportional (Less fluid=less permeable, more fluid=more permeable)

Question 22

What are saturated areas in the membrane and what do they look like

Answer 22

-Less fluid and permeable
-Lipid rafts
-High in cholesterol
-Straight, saturated, tightly packed fatty acid tails

Question 23

Do all cell membranes have the same fluidity?

Answer 23

-NO
-Using FRAP, it was proven molecules making up the nucleus do not move around, but they do in the endoplasmic reticulum

Question 24

In what order do cells break down macromolecules for energy and when

Answer 24

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

Question 25

How do camels tolerate their environment

Answer 25

-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

Question 26

How do geese manage energy for migration

Answer 26

-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

Question 27

How do bar headed geese survive low O2 environments

Answer 27

-Can fly as high as mt. everest
-Large lungs, more surface area for O2 intake
-Better breathing patterns
-More cappillaries and mitochondria