Biology - MCAT Biological and Biochemical Foundations of Living Systems
Card 0 of 11296
Which hormone is most responsible for decreased levels of blood calcium?
Which hormone is most responsible for decreased levels of blood calcium?
Calcitonin lowers plasma calcium, while parathyroid hormone (PTH) increases it. Insulin and glucagon are responsible for blood glucose, not calcium.
Calcitonin lowers plasma calcium, while parathyroid hormone (PTH) increases it. Insulin and glucagon are responsible for blood glucose, not calcium.
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Which important structure(s) line the small intestine and are key for maximizing nutrient absorption?
Which important structure(s) line the small intestine and are key for maximizing nutrient absorption?
Microvilli surround villa which line the small intestine. These structures greatly increase the surface area (and therefore nutrient absorption capability) of the small intestine.
Microvilli surround villa which line the small intestine. These structures greatly increase the surface area (and therefore nutrient absorption capability) of the small intestine.
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A certain type of plant is only tall when it has a heterozygous genotype. If two heterozygous plants are crossed, what is the probability their offspring will also be tall?
A certain type of plant is only tall when it has a heterozygous genotype. If two heterozygous plants are crossed, what is the probability their offspring will also be tall?
The cross between two heterozygous plants (Tt and Tt) will result in 25% TT, 50% Tt and 25% tt.
The cross between two heterozygous plants (Tt and Tt) will result in 25% TT, 50% Tt and 25% tt.
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What is the means by which organisms maintain a constant internal environment in spite of fluctuations in the external environment?
What is the means by which organisms maintain a constant internal environment in spite of fluctuations in the external environment?
Homeostasis, or "steady-state" physiology, is the system of feedback loops that enables an organism to create a stable, adaptive environment. For example, the pancreas and the brain together work to regulate the blood sugar levels via the hormones insulin and glucagon.
Homeostasis, or "steady-state" physiology, is the system of feedback loops that enables an organism to create a stable, adaptive environment. For example, the pancreas and the brain together work to regulate the blood sugar levels via the hormones insulin and glucagon.
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Gram staining prepares bacteria to be visualized under light microscope.
What allows a bacteria to stain positively with gram stain?
Gram staining prepares bacteria to be visualized under light microscope.
What allows a bacteria to stain positively with gram stain?
Gram-positive bacteria are able to retain the crystal violet stain found in gram stain because of their thick peptidoglycan cell walls. Consequently, these bacteria stain dark blue or purple by gram staining. Alternatively, gram-negative bacteria appear red or pink because they are unable to retain the dye due to thinner cell walls and less peptidoglycan.
Gram-positive bacteria are able to retain the crystal violet stain found in gram stain because of their thick peptidoglycan cell walls. Consequently, these bacteria stain dark blue or purple by gram staining. Alternatively, gram-negative bacteria appear red or pink because they are unable to retain the dye due to thinner cell walls and less peptidoglycan.
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Which of the following would not be found an E. Coli sample?
Which of the following would not be found an E. Coli sample?
E. Coli is a type of bacteria. Because bacteria are prokaryotes, they do not contain membrane-bound organelles. A nucleus is a membrane-bound organelle and therefore would not be found in bacteria.
E. Coli is a type of bacteria. Because bacteria are prokaryotes, they do not contain membrane-bound organelles. A nucleus is a membrane-bound organelle and therefore would not be found in bacteria.
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Haversian systems are found in which of the following?
Haversian systems are found in which of the following?
Compact and spongy bone have similar chemical and structural compositions and are both hard and resistant to compression; however, due to the fact that compact bone is denser, nutrients are delievered through canals called Haversian systems in compact bone; spongy bone is less dense and lacks these specialized canals.
Compact and spongy bone have similar chemical and structural compositions and are both hard and resistant to compression; however, due to the fact that compact bone is denser, nutrients are delievered through canals called Haversian systems in compact bone; spongy bone is less dense and lacks these specialized canals.
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All of the following are true about bacilli bacteria except:
I. All bacilli are rod-shaped
II. All bacilli are gram positive
III. All bacilli are aerobic
All of the following are true about bacilli bacteria except:
I. All bacilli are rod-shaped
II. All bacilli are gram positive
III. All bacilli are aerobic
Bacilli is a genus of bacteria that are characterized by their rod-shaped cells. Bacilli can be either gram positive, such as Bacillus anthracis, or gram negative, such as Salmonella enterica. Bacilli bacteria can be either aerobic (require oxygen) or facultative anaerobes (can thrive in both oxygen rich and oxygen poor environment). Bacilli are not exclusively aerobic, nor are they exclusively gram positive.
Bacilli is a genus of bacteria that are characterized by their rod-shaped cells. Bacilli can be either gram positive, such as Bacillus anthracis, or gram negative, such as Salmonella enterica. Bacilli bacteria can be either aerobic (require oxygen) or facultative anaerobes (can thrive in both oxygen rich and oxygen poor environment). Bacilli are not exclusively aerobic, nor are they exclusively gram positive.
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Where is blood pressure the greatest?
Where is blood pressure the greatest?
Blood pressure tends to be the greatest near the heart, and decreases as blood flows to the capillaries. The pressure is greatest at the aorta and gradually decreases as blood moves from the aorta to large arteries, smaller arteries, and capillaries. The pressure is lowest in the venous system, which is why blood can pool in the veins and act as a "blood reservoir". Veins contain valves that allow them to pump blood back to the heart.
Blood pressure tends to be the greatest near the heart, and decreases as blood flows to the capillaries. The pressure is greatest at the aorta and gradually decreases as blood moves from the aorta to large arteries, smaller arteries, and capillaries. The pressure is lowest in the venous system, which is why blood can pool in the veins and act as a "blood reservoir". Veins contain valves that allow them to pump blood back to the heart.
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What characteristic do both all plants and fungi have in common?
What characteristic do both all plants and fungi have in common?
Both plants and fungi consist of eukaryotic cells. Their cells contain membrane-enclosed nuclei and organelles which is a defining characteristic of eukaryotic cells.
Fungi do not photosynthesize. While seedless plants and fungi use spores, this trait is not common to all plants. Plant cell walls are composed of collagen, while fungi use chitin.
Both plants and fungi consist of eukaryotic cells. Their cells contain membrane-enclosed nuclei and organelles which is a defining characteristic of eukaryotic cells.
Fungi do not photosynthesize. While seedless plants and fungi use spores, this trait is not common to all plants. Plant cell walls are composed of collagen, while fungi use chitin.
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In what form is carbon dioxide usually circulated in human blood?
In what form is carbon dioxide usually circulated in human blood?
Carbon dioxide is usually circulated in human blood in the form of 
, or bicarbonate. This is an important part of the blood buffering system, as the bicarbonate ion is the conjugate base of carbonic acid.
Carbon dioxide is usually circulated in human blood in the form of
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Heart burn is experienced when stomach acid and contents enter the esophagus through which sphincter?
Heart burn is experienced when stomach acid and contents enter the esophagus through which sphincter?
The lower esophageal sphincter separates the esophagus from the stomach. When stomach acid and contents leak through the lower esophageal sphincter, the acid irritates the esophagus and can lead to pain around the area of the heart. The heart is not actually affected.
The lower esophageal sphincter separates the esophagus from the stomach. When stomach acid and contents leak through the lower esophageal sphincter, the acid irritates the esophagus and can lead to pain around the area of the heart. The heart is not actually affected.
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In mammals, what muscles are involved in inhalation?
In mammals, what muscles are involved in inhalation?
During inhalation, the external intercostal muscles and diaphragm both contract to help expand the thoracic cavity and draw in air. The internal intercostal muscles are involved in exhalation, and compress the thoracic cavity during contraction.
During inhalation, the external intercostal muscles and diaphragm both contract to help expand the thoracic cavity and draw in air. The internal intercostal muscles are involved in exhalation, and compress the thoracic cavity during contraction.
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Which two muscles do humans use primarily for inhalation?
Which two muscles do humans use primarily for inhalation?
The two muscles that help with breathing are the diaphragm and the external intercostal muscles. The diaphragm pulls the thoracic cavity downward and the external intercostal muscles expand the cavity outward. This expansion of the thoracic cavity leads to a decrease in pressure and allows air to be drawn into the lungs.
The two muscles that help with breathing are the diaphragm and the external intercostal muscles. The diaphragm pulls the thoracic cavity downward and the external intercostal muscles expand the cavity outward. This expansion of the thoracic cavity leads to a decrease in pressure and allows air to be drawn into the lungs.
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A new species found by scientists exhibits indeterminate cleavage up to the third cleavage. If all of the cells in the embryo are separated and incubated in healthy conditions on their own after the third cleavage, how many organisms will develop?
A new species found by scientists exhibits indeterminate cleavage up to the third cleavage. If all of the cells in the embryo are separated and incubated in healthy conditions on their own after the third cleavage, how many organisms will develop?
After the third cleavage, the embryo would be composed of 8 cells. If every cleavage step up up to this point was indeterminate, then each cell still has the necessary components to develop into a complete organism. The result would be 8 genetical identical organisms.
After the third cleavage, the embryo would be composed of 8 cells. If every cleavage step up up to this point was indeterminate, then each cell still has the necessary components to develop into a complete organism. The result would be 8 genetical identical organisms.
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Which structures contain deoxygenated blood?
Which structures contain deoxygenated blood?
When blood returns to the heart via the superior and inferior vena cavae, it is deoxygenated. It remains this way as it passes through the right atrium, the right ventricle, and the pulmonary arteries, through which it travels to the lungs to conduct gas exchange with the alveoli. Both the right ventricle and the pulmonary artery contain deoxygenated blood.
All of the other answer choices contain at least one component that carries oxygenated blood.
When blood returns to the heart via the superior and inferior vena cavae, it is deoxygenated. It remains this way as it passes through the right atrium, the right ventricle, and the pulmonary arteries, through which it travels to the lungs to conduct gas exchange with the alveoli. Both the right ventricle and the pulmonary artery contain deoxygenated blood.
All of the other answer choices contain at least one component that carries oxygenated blood.
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What is embryonic cleavage?
What is embryonic cleavage?
Embryonic cleavage is the division of cells without cell growth. Once an ovum is fertilized by a sperm cell, it is called a zygote. The zygote undergoes multiple rapid cell cycles (rounds of mitosis) without significant growth, producing a dense cluster of cells that is the same size as the original zygote. This process is called cleavage.
Embryonic cleavage is the division of cells without cell growth. Once an ovum is fertilized by a sperm cell, it is called a zygote. The zygote undergoes multiple rapid cell cycles (rounds of mitosis) without significant growth, producing a dense cluster of cells that is the same size as the original zygote. This process is called cleavage.
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An antifungal cream advertises to chemically attack the fungal cells without harming the skin. The antifungal chemical most likely acts on which of the following?
An antifungal cream advertises to chemically attack the fungal cells without harming the skin. The antifungal chemical most likely acts on which of the following?
The antifungal compound is likely specific to chitin, as it is a common material of many fungi cell wall structures. Chitin is resistant to breakdown, and is actually found in insect exoskeletons. The incorrect answers are found in skin cells as well as fungal cells, and would harm the skin if the chemical attacked these structures.
The antifungal compound is likely specific to chitin, as it is a common material of many fungi cell wall structures. Chitin is resistant to breakdown, and is actually found in insect exoskeletons. The incorrect answers are found in skin cells as well as fungal cells, and would harm the skin if the chemical attacked these structures.
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Which of these processes is the means by which a bacterium can directly uptake and incorporate foreign DNA from the environment into its genome?
Which of these processes is the means by which a bacterium can directly uptake and incorporate foreign DNA from the environment into its genome?
Transformation is defined as the process by which bacteria can incorporate exogenous DNA from the environment into their genome via direct uptake. Transduction and conjugation are also processes by which exogenous DNA is incorporated, but involve other methods.
Transformation is defined as the process by which bacteria can incorporate exogenous DNA from the environment into their genome via direct uptake. Transduction and conjugation are also processes by which exogenous DNA is incorporated, but involve other methods.
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Which of the following structures does not arise from the mesoderm?
Which of the following structures does not arise from the mesoderm?
The mesoderm gives rise to muscles, bones, the circulatory system, the gonads, and the kidneys. Think of the mesoderm as the means by which your body gets around on a daily basis: muscles and bones, heart to pump blood, and kidneys to excrete waste.
The respiratory system arises from the endoderm.
The mesoderm gives rise to muscles, bones, the circulatory system, the gonads, and the kidneys. Think of the mesoderm as the means by which your body gets around on a daily basis: muscles and bones, heart to pump blood, and kidneys to excrete waste.
The respiratory system arises from the endoderm.
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