Valuable molecules as glucose and amino acids

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Reference no: EM1391460

Urine excreted by mammals contains many valuable molecules such as glucose and amino acids, but they are at much lower concentration in excreted urine than in blood. What accounts for such low concentrations in urine?
Answer
1.
The molecules are too big to fit through the filter in the glomerulus.
2.
The molecules diffuse out of urine and back into blood in the descending limb of the loop of Henle.
3.
Facilitated diffusion channels in collecting tubules allow them to move out of urine.
4.
The valuable molecules are retrieved from urine in the proximal tubules.
3 points
Question 21


A crayfish moves from a bubbly, swift-flowing creek into a stagnant pool. If it stays in the pool what must it also do?
Answer
1.
Stop moving.
2.
Reduce the amount of food it eats.
3.
Look for and consume more food.
4.
Leave the water.
3 points
Question 22


Where do air-breathing insects carry out exchange of oxygen and carbon dioxide?
Answer
1.
in specialized external gills
2.
in specialized internal gills
3.
in the alveoli of their lungs
4.
across the plasma membranes of cells
5.
across the thin external cuticular
3 points
Question 23


Which one of the following nitrogenous wastes requires the least water for its excretion?
Answer
1.
amino acids
2.
urea
3.
uric acid
4.
ammonia
3 points
Question 24


The advantage of excreting wastes as urea rather than as ammonia is that
Answer
1.
urea can be exchanged for Na+.
2.
urea is less toxic than ammonia.
3.
urea requires more water for excretion than ammonia.
4.
urea does not affect the osmolarity gradient.
5.
less nitrogen is removed from the body.
3 points
Question 25


Tissue cells of ectotherms contain, on average, fewer mitochondria than similar cells of endotherms. What%u2019s the best explanation for this difference?
Answer
1.
Ectotherms can%u2019t move as rapidly as endotherms can.
2.
Ectotherms don%u2019t regulate their body temperature.
3.
Endotherms more effectively insulate their bodies so as to reduce heat loss.
4.
Ectotherms tend to grow throughout their lives.
3 points
Question 26


To increase the effectiveness of exchange surfaces in the linings of lungs and the intestines, evolutionary pressures have
Answer
1.
increased the surface area available for exchange.
2.
increased the thickness of these linings.
3.
increased the number of cell layers.
4.
decreased the metabolic rate of the cells in these linings.
5.
increased the volume of the cells in these linings.
3 points
Question 27


Protein kinases are enzymes which
Answer
1.
function as a second messenger molecule
2.
serve as a receptor for various signal molecules
3.
produce second messenger molecules
4.
activate or inactivate other proteins by adding a phosphate group to them
3 points
Question 28


Frequently, very few molecules of a hormone are required to cause changes in a target cell. This is because
Answer
1.
hormones are large molecules that remain in circulation for months and can repeatedly stimulate the same cell.
2.
the mechanism of hormonal action involves an enzyme cascade that amplifies the response to a hormone.
3.
the mechanism of hormonal action involves the rapid replication of the hormone within the target cell.
4.
hormones are lipid-soluble and readily penetrate the membranes of the target cell.
3 points
Question 29


Why does the plant Arabidopsis have 5 different genes that code for 5 different forms of phytochrome?
Answer
1.
Several of them sense red light and the others sense far-red light.
2.
They mediate different types of responses to red and far-red light.
3.
Some of the phytochrome types do not function in light absorption but regulate other processes.
4.
All 5 phytochrome types absorb different colors of light, maximizing sensitivity of the plant to light.
3 points
Question 30


The advantage of excreting wastes as urea rather than as ammonia is that
Answer
1.
urea can be exchanged for sodium ions.
2.
urea is less toxic than ammonia.
3.
urea requires more water for excretion than ammonia excretion requires.
4.
urea does not affect the osmolar gradients in the kidney.
3 points
Question 31


How do small molecules in blood get out of a blood vessel and into nearby tissue?
Answer
1.
They diffuse in the space between the edges of neighboring capillary endothelial cells.
2.
Active transport.
3.
Simple diffusion directly through the capillary endothelial cell plasma membrane.
4.
Capillaries lead into lymphatic vessels and the molecules diffuse out through numerous open spaces in the lymph vessel walls.
3 points
Question 32


Plants often use changes in day length (photoperiod) to trigger events such as dormancy and flowering. It is logical that plants have evolved this mechanism because photoperiod changes
Answer
1.
Are more predictable than air temperature changes.
2.
Alter the amount of energy available to the plant.
3.
Are modified by soil temperature changes.
4.
Are correlated with moisture availability.
3 points
Question 33


An organism that has only behavioral controls over its body temperature is the
Answer
1.
penguin.
2.
bluefin tuna.
3.
green frog.
4.
house sparrow.
5.
gray wolf.
3 points
Question 34


Large, flightless birds such as ostriches and emus can run long distances at high speeds, something their mammalian predators cannot do. What is it about ratites and mammals that can explain this difference?
Answer
1.
Ratites have more elastic tissue in their tendons than mammals do.
2.
Ratites have longer legs relative to body weight than mammals do.
3.
Mammal hearts cannot beat as fast as a ratite%u2019s can.
4.
Unlike mammals, ratite respiratory systems have no residual volume, the air that cannot be exhaled.
3 points
Question 35


The ripening of fruit and the dropping of leaves and fruit are principally controlled by
Answer
1.
auxins
2.
cytokinins
3.
carbon dioxide concentration in the air
4.
ethylene
3 points
Question 36


Gravitropism in plant roots appears to be mediated by:
Answer
1.
The lack of red light in the soil.
2.
Starch granules that move down a gravitational field.
3.
Signaling from root cap cells.
4.
Increased division of root apical meristem cells on the side nearest the surface of the soil.
3 points
Question 37


An overheated and sick dog has an impaired thermoregulatory response if it
Answer
1.
increases its evaporative heat loss.
2.
relocates itself to a cooler location.
3.
increases its body temperature to match the environmental temperature.
4.
increases vasodilation in its blood vessels near the skin.
3 points
Question 38


Which of the following animals generally has the lowest volume of urine production?
Answer
1.
a marine bony fish
2.
a salmon in freshwater
3.
a freshwater bony fish
4.
a marine shark
3 points
Question 39


When a protein hormone binds to a receptor protein located in a cell%u2019s plasma membrane the cell often does something in response to the hormone. How does the signal get into the cell%u2019s cytoplasm?
Answer
1.
The receptor protein changes shape and in its new shape can interact with proteins inside the cell.
2.
The hormone diffuses across the cell membrane and activates enzymes inside the cell.
3.
The hormone binds to the receptor and causes the receptor to enter the cell, stimulating enzymes inside.
4.
The protein hormone is degraded to amino acids by digestive enzymes and the amino acids enter the cell through channels to increase the cell%u2018s metabolic rate.

 

Reference no: EM1391460

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