E155 If an animal is frozen solid, is it dead?

What is a cryoprotectant?

A substance that protects biological samples, cells, or tissues from damage during freezing and thawing”

Why do the frogs need to conserve fuel during the winter?

To fuel post-winter reproduction 

What is the source of the glucose that circulates throughout the frog’s body?

Glucose from glycogen (acts as a cryoprotectant) 

What metabolic fuels do the frogs use when they are frozen versus unfrozen?

• Unfrozen: lipids

• Carbs fuel metabolism during cooling, freezing and thawing, and when frozen

How many freeze-thaw cycles might happen during a single winter?

23 cycles 

Where were the two populations of frogs from?

 Alaska and Ohio 

Researchers measure two cryoprotectants. What were they?

Glycogen and urea 

Which population had a higher capacity for glucose synthesis?

Alaskan frogs 

Which population experienced more stress during the freeze-thaw process?

Ohio frogs 

Which organ heats up first when the squirrel is aroused from sleep?

Brain

How often does it have to wake-up during the winter?

Every 10 days

What is a possible advantage of allowing some neural deterioration during hibernation?

• Stripped-down brain could save a lot of energy 

• Their brains degrade far less and rebound more quickly than expected

• Synaptic plasticity 

• Shorter and less branching dendrites 

• Dendrites had fewer spines 

• Afterward, dendrites were more bushy and bigger cell bodies

What is the function of glucose during the freezing process?

• Liver makes glucose to mix with the urine and blood to create antifreeze in cold conditions

• Goes into the frog’s cells to prop them up 

• Prevents too much water from being drawn out by the ice outside the cells

For many years does a caterpillar go through freezing and thawing cycles before it can reproduce?

7 years 

what happens if our skin freezes

frostnip = red

superficial frostbite = blister

deep frostbite = dead skin

fat bodies on frogs

store energy, but not used as insulation in the same way as humans

what might happen to the frogs if there are more freeze-thaw cycles per winter

shift from glycogen to glucose

• lipids in warm temp (lipids → acetyl CoA → mitochondria O2

which population of frogs use glycogen more efficiently

alaskan frogs are more efficient than the ohio ones

which population of frogs acculumates urea

alaskan

if salt is so great for decreasing the freezing point, why not accumulate salt?

salt messes up the membrane potentials

• urea is an organic osmolyte that adjusts osmolarity

how did they known which species was more stressed

stress = amount of Hb and lactate in plasma

• more stress in the Ohio frog because greater Hb and lactate levels

deserts

defined by lack of H2O

why are most deserts near 30 N and 30 S latitude

hadley cells

1. hot air rises

2. warm air holds H2O

3. H2O condenses out of the cold air

hadley cells in the tropics

hot air rises and condesnese then rains

hadley cells in temperatre temperatures

cold air sinks in socal

hadley cells in pacific northwest

hot air rises, then condenses at the cold

rain shadows

ocean brings humid air up a mountain, then rains and snows

• dry air moves down the mountain toward deserts