IB Bio

In an experiment on osmosis, red blood cells were immersed in a salt solution for two hours. The micrographs show the appearance of these cells before and after immersion in the salt solution. What explains the observed changes?

• The salt solution was hypertonic and entered the red blood cells.

• The salt solution was hypotonic and disrupted the membranes of the red blood cells.

• The salt solution was hypertonic and water moved into it from the red blood cells.

• The salt solution was hypotonic and minerals salts were lost from the red blood cells.

What can cause an enzyme to be denatured?

• Binding the enzyme to the substrate

• Cooling the enzyme to 50C below optimum temperature

• Changing the pH

• Inactivating the enzyme gene.

What property of water makes it possible for insects to walk on its surface?

• Adhesion of water molecules

• Cohesion of water molecules

• High specific heat capacity

• High density

Answer explanation

The property that allows insects to walk on water is the cohesion of water molecules. This cohesion creates surface tension, enabling small insects to stay on the surface without sinking.

Where do hydrogen bonds form?

• Between the slight negative charge of hydrogen and slight positive charge of oxygen within a water molecule

• Between the slight positive charge of hydrogen and slight negative charge of oxygen within a water molecule

• Between the slight positive charge of hydrogen and slight negative charge of oxygen in different water molecules

• Between the slight negative charge of hydrogen and slight positive charge of oxygen in different water molecules

Answer explanation

Hydrogen bonds form between the slight positive charge of hydrogen in one water molecule and the slight negative charge of oxygen in another water molecule, allowing for the unique properties of water.

Tags

NGSS.HS-ESS2-5

What cell component is found in eukaryotic cells but not in prokaryotic cells?

• Mitochondria for respiration

• DNA containing genetic information

• Ribosomes for protein synthesis

• Cell wall to maintain shape

Answer explanation

Mitochondria are organelles responsible for respiration and energy production, and they are present in eukaryotic cells but absent in prokaryotic cells. The other options, such as DNA and ribosomes, are found in both cell types.

Tags

NGSS.HS-LS1-7

What is a consequence of anaerobic cell respiration in muscles?

• Large yield of readily available ATP and ethanol production

• Small yield of readily available ATP and lactate accumulation

• Large yield of ATP and production of carbon dioxide and lactic acid

• Small yield of ATP that is not readily available and carbon dioxide production

Answer explanation

Anaerobic respiration in muscles results in a small yield of ATP due to the lack of oxygen. This process leads to lactate accumulation, which can cause muscle fatigue, making the correct choice "Small yield of readily available ATP and lactate accumulation."

Tags

NGSS.HS-LS2-3

Which process is an example of catabolism?

• Translation of mRNA

• Replication of DNA

• Hydrolysis of protein

• Synthesis of a disaccharide

What occurs during the establishment of a resting membrane potential of a neuron?

• Both sodium and potassium ions are pumped outside the neuron.

• Sodium ions are pumped out while potassium ions are pumped into the neuron.

• Both sodium and potassium ions are at rest inside the membrane of the neuron.

• Sodium ions leave by diffusion and potassium ions enter the neuron by active transport.

Tags

NGSS.HS-LS1-3

Stargardt’s disease, a genetic disorder that causes vision loss, is being treated using retinal cells derived from human embryonic stem cells. Why are embryonic stem cells used?

• They are already specialized for this function.

• They are able to differentiate into the required cell type.

• They retain stem cell properties after specialization.

• There are no ethical issues concerning their use.

Tags

NGSS.HS-LS1-4

A molecule of DNA is found to contain 200 guanine bases, representing 25% of the total number of bases. How many phosphate groups does this molecule of DNA contain?

• 50

• 200

• 800

• 1000