2.3 Metabolic rate

Question 1

definition of metabolic rate?

Answer 1

the metabolic rate of an organism is the amount of energy used in a given period of time

it refers to the speed at which glucose is broken down to release energy (ATP), carbon dioxide and water during cell respiration

Question 2

How can the rate of metabolism of different organisms be compared?

Answer 2

Measuring
oxygen consumption per unit
carbon dioxide output
energy output in the form of heat per unit time

Question 3

How can oxygen consumption per unit be measured?

Answer 3

using a respirometer

Question 4

Explain how a respirometer is used?

Answer 4

Respirometers measures rate of respiration of an organism.
Carbon dioxide given out by an organism as a waste product is absorbed by the carbon dioxide
Oxygen taken in by the organism causes a decrease in volume of the enclosed gas.
This causes the coloured liquid to rise
After a known length of time, the syringe is used to find the volume of air which must be injected to return the coloured liquid to its original level. The control includes an inert material such as glass beads equal in the volume to the organism (to make the experiment fair and have only one variable factor)
This measure is carried out as it could be argued that the observed results were simply due to space being occupied in the respirometer and not to the organism respiring
The experiment should be carried out in a water bath to ensure a constant temperature.
Again this makes sure the experiment is fair with only one variable factor.

Question 5

How do you measure energy production as heat per unit time?

Answer 5

Calorimeter

Question 6

What is a calorimeter?

Answer 6

A calorimeter is a well insulated container containing a pipe through which water flows
Heat generated by the organism causes a rise in temperature of the water in the pipe
By measuring the temperature difference in the water entering and leaving the calorimeter for given period of time, the organisms metabolic rate can be calculated

Question 7

What is the basal metabolic rate?

Answer 7

the minimum rate of energy release needed by an endotherm to maintain essential body processes

Question 8

What is the oxygen delivery in complex organisms that have a high metabolic rate?

Answer 8

High metabolic rate = greater demand for oxygen

These organisms have evolved efficient cardiovascular transport systems to deliver oxygen from lungs to the body cells

Question 9

Explain single circulatory system and one example?

Answer 9

Fish have a single circulatory system which has a heart with two chambers - one atrium and one ventricle
blood passes through the heart once in each complete circuit of the body
As the pressure drops as the blood passes through the capillary bed in the gills, blood is delivered to the body tissues at low pressures.

Question 10

Explain incomplete double circulatory system and one example?

Answer 10

Amphibians and most reptiles have incomplete double circulatory systems
Their hearts have three chambers - two atria and one ventricle
The right atrium receives deoxygenated blood returning from the body tissues
The left atrium receives oxygenated blood from the lungs
Blood from both atria is passed into one ventricle which means that oxygenated and deoxygenated blood mix before being pumped to the body tissues.

Question 11

Explain complete double circulatory system and one example?

Answer 11

Birds and mammals have a complete double circulatory system
The heart has four chambers - two atria and two ventricles, allowing complete separation of oxygenated and deoxygenated blood this is therefore complete circulation

Question 12

Describe the lungs of amphibians?

Answer 12

small balloon like sacs
inefficient system as surface area for diffusion is low being limited to the outer surface of the lungs
the amount of oxygen obtained through the amphibian lungs is small
To ensure the animal has enough to support its metabolic rate, uptake is mostly by diffusion through the animals moist skin and mouth

Question 13

Describe the lungs of reptiles?

Answer 13

each lung is divided into several alveolar type sacs, increasing the surface area over which diffusion can take place

Question 14

Describe the lungs of mammals?

Answer 14

The lungs in mammals contain millions of tiny alveoli which provided a very large surface area for diffusion
Breathing movements of the diaphragm and ribcage bring about emptying and filling the lungs under negative pressure

Question 15

Describe the lungs of birds?

Answer 15

diffusion of oxygen takes place through a series of parallel tubes in the lungs called parabronchi
Air is passed through the tubes in one direction only through the filling and emptying of air sacs which lie outside the lungs
Inhalation causes fresh air to be drawn into the posterior air sacs, while stale used air sacs air leaves the lungs to enter the anterior air sacs
On exhaling the posterior air sacs push oxygen - rich air into the lungs and stale air from the anterior air sacs passes into the trachea
this unidirectional air flow presents the mixing of inhaled and exhaled air, maximising the oxygen content of the air
This is important as flight at high altitude has high metabolic needs in a low oxygen environment

Question 16

give the meaning of the term adaptation?

Answer 16

special feature of an organism that gives it the ability to survive in its environment

Question 17

Give the meaning of the term niche?

Answer 17

the role an organism it plays in its community defined by for example
predators
temperature
oxygen availability

Question 18

What is haemoglobin?

Answer 18

protein found in red blood cells

Question 19

What must diving animals cope with?

Answer 19

Limited supply of oxygen

increase in pressure with increasing water depth

Question 20

As the depth of the water increases what happens to the diving animal?

Answer 20

as it increases, the increase in pressure causes and increase in solubility of gases within the tissue resulting in tissues becoming saturated

Question 21

How can nitrogen and oxygen at high concentrations have serious effects on the body?

Answer 21

nitrogen poisoning causes euphoria and delusions similar to a narcotic effect
Oxygen is toxic at high pressure and can result in blackout or death

Question 22

What happens when the diving animal surfaces?

Answer 22

gases move out of the tissues and back into the blood

Question 23

Why must a human diver ascend slowly?

Answer 23

to prevent these gases coming out of solution and forming bubbles in the blood (the bends)

Question 24

What are some adaptations in marine animals that allow them to dive successfully?

Answer 24

changes to blood flow, metabolism and an increase in oxygen storage capacity

Question 25

Lung adaptation?

Answer 25

some deep diving animals have compliant chest walls and lungs which collapse as the animal dives
Lung collapse begins in the alveoli, pushing air up into the larger air passages and preventing diffusion of gases into the blood
Specialised surfactant helps to re inflate the lungs as the animal returns to the surface

Question 26

What is the benefit of lung adaptation?

Answer 26

reduces the risk of oxygen toxicity and nitrogen narcosis and decompression sickness

Question 27

Blood flow and heart rate adaptations?

Answer 27

Blood is diverted to the heart, brain and lungs
There is a decrease in cardiac output and total blood flow
Heart rate is decreased

Question 28

What is the benefit of blood flow and heart rate adaptation?

Answer 28

blood is diverted to essential organs

Assists in lowering metabolic rate

Question 29

Red blood cells and haemoglobin adaptation?

Answer 29

RBC are stored in the spleen and released into the blood during deeper dives
This increases the haemocrit (percentage of RBC in a given volume of blood)
The volume of blood is also relatively greater per unit of body mass in deep diving animals
Increased number of red blood cells and larger volume of blood gives an increase in haemoglobin

Question 30

What is the benefit of red blood cells and haemoglobin adaptations?

Answer 30

More haemoglobin is available for transport of oxygen

Question 31

Myoglobin adaptation?

Answer 31

Diving animals have myoglobin concentration in their muscles which is up to 80% greater than their land, living relatives

Question 32

What is the benefit of myoglobin adaptation?

Answer 32

myoglobin provides a store of oxygen active muscle cells

Question 33

Metabolism Adaptation?

Answer 33

Some diving animals exhibit a lowered metabolism due to the need to respire anaerobically. This may be associated with increased concentrations of enzymes involved in the removal of lactate.

Question 34

What is the benefit of Metabolism adaptation?

Answer 34

accomodates reduced synthesis of ATP in anaerobic respiration

Question 35

Explain High altitude niche?

Answer 35

At both sea level and at high altitude, the concentration of oxygen in the air is 12%
At high altitudes the atmosphere is less dense with gas molecules spaced further apart
This makes it more difficult for oxygen to diffuse through the alveolar wall into the blood causing oxygen deprivation (hypoxia)

Question 36

Describe Altitude Sickness?

Answer 36

Symptoms - vomitting, headache, fatigue and confusion
In severe cases cerebral and pulmonary edema result in the accumulation of fluid around the brain and haemoglobin in the lungs
The increased stress placed on the lungs and cardiovascular system can also result in heart failure.

Question 37

Explain altitude training?

Answer 37

when humans live at lower altitudes and travel to high altitude, the immediate response is an increase in heart and breathing rates as the body works harder to get oxygen into the blood
Over the next few weeks the body becomes acclimatised, it produces more red blood cells and develops a more extensive capillary network
Endurance athletes often train at high altitude in the run up to major championships in order to benefit from these physiological changes
Within weeks of return to sea level the body returns to normal

Question 38

Adaptations in high altitude niches?

Answer 38

humans who live constantly at high altitudes have evolved to survive

Question 39

Lungs adaptation and benefit?

Answer 39

pulmonary capacity and breathing rate increases

benefit - allows for increased diffusion of gases

Question 40

Haemoglobin adaptation and benefit?

Answer 40

some population have increased levels of haemoglobin

benefit - to maximise oxygen transport

Question 41

cardiovascular adaptation and benefit?

Answer 41

RBC numbers increase in capillary networks in muscles. Blood vessels are broader
benefit - to maximise oxygen transport

Question 42

what is VO2 max?

Answer 42

VO2 max is the maximum volume of oxygen that a person is able to breathe in during strenuous exercise

Question 43

what is VO2 max used to measure?

Answer 43

the efficiency of the cardiovascular system

The higher the VO2 value the more efficient the metabolism and cardiovascular system

Question 44

Method to measure VO2 max?

Answer 44

it is measured using a procedure involving an ergometer - a treadmill or exercise bike
VO2 max is reached when the oxygen uptake stays steady even when the workload continues to be increased
it improves with training