HESI A2 — All Questions

Which organelle is known as the 'powerhouse of the cell'?

• a.Nucleus
• b.Golgi apparatus
• c.Ribosome
• d.Mitochondrion✓

The mitochondrion produces most of the cell's energy in the form of ATP through cellular respiration. This role earns it the nickname powerhouse of the cell.

What is the basic structural and functional unit of all living organisms?

• a.The tissue
• b.The cell✓
• c.The atom
• d.The organ

The cell is the smallest unit that can carry out all life processes. All living organisms are made of one or more cells.

Which blood cells are primarily responsible for carrying oxygen?

• a.Red blood cells✓
• b.Plasma cells
• c.Platelets
• d.White blood cells

Red blood cells contain hemoglobin, a protein that binds oxygen. They transport oxygen from the lungs to the body's tissues.

At 25 degrees C, what is the pH of a neutral solution such as pure water?

• a.7✓
• b.1
• c.0
• d.14

At 25 degrees C the pH scale runs 0 to 14, with 7 neutral, values below 7 acidic, and values above 7 basic. Pure water is neutral at pH 7 at this temperature. Water stays neutral at other temperatures, but the neutral pH value shifts slightly because the ionization of water is temperature dependent.

Which system is responsible for pumping blood throughout the body?

• a.The respiratory system
• b.The digestive system
• c.The skeletal system
• d.The circulatory system✓

The circulatory system, centered on the heart and blood vessels, moves blood throughout the body. It delivers oxygen and nutrients and removes wastes.

What gas do humans breathe in that is essential for cellular respiration?

• a.Oxygen✓
• b.Helium
• c.Nitrogen
• d.Carbon dioxide

Cells use oxygen to break down glucose and release energy during cellular respiration. Humans inhale oxygen and exhale carbon dioxide as a waste product.

Which part of the cell contains the genetic material (DNA)?

• a.The nucleus✓
• b.The cytoplasm
• c.The cell membrane
• d.The vacuole

The nucleus houses the cell's DNA, which carries genetic instructions. It acts as the control center that directs cell activities.

What is the smallest unit of an element that retains its properties?

• a.A molecule
• b.A tissue
• c.A cell
• d.An atom✓

An atom is the smallest particle of an element that still has the properties of that element. Atoms combine to form molecules.

Which type of blood vessel carries blood away from the heart?

• a.Veins
• b.Venules
• c.Arteries✓
• d.Capillaries

Arteries carry blood away from the heart to the body's tissues. Veins, by contrast, return blood to the heart.

What is the largest organ of the human body?

• a.The heart
• b.The skin✓
• c.The liver
• d.The lungs

The skin is the body's largest organ by weight, making up roughly 16 percent of body mass. It protects the body, helps regulate temperature, and provides sensation.

Which nutrient is the body's primary source of quick energy?

• a.Carbohydrates✓
• b.Triglycerides
• c.Electrolytes
• d.Amino acids

Carbohydrates are broken down into glucose, which cells use for quick energy. They are the body's preferred and fastest energy source.

In chemistry, a substance that donates hydrogen ions and has a pH below 7 is called:

• a.An acid✓
• b.A base
• c.A salt
• d.A neutral

An acid releases hydrogen ions in solution and has a pH lower than 7. Bases, in contrast, have a pH above 7.

Which system includes bones, joints, and cartilage that support the body?

• a.The skeletal system✓
• b.The endocrine system
• c.The nervous system
• d.The muscular system

The skeletal system is made up of bones, joints, and cartilage. It provides structure, protects organs, and allows movement together with muscles.

What process do plants use to convert sunlight into chemical energy?

• a.Digestion
• b.Fermentation
• c.Respiration
• d.Photosynthesis✓

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to make glucose and oxygen. It converts light energy into stored chemical energy.

Which organ filters waste from the blood and produces urine?

• a.The lungs
• b.The stomach
• c.The kidney✓
• d.The pancreas

The kidneys filter waste products and excess water from the blood, forming urine. This helps maintain the body's fluid and chemical balance.

What is the control center of the nervous system?

• a.The brain✓
• b.The heart
• c.The liver
• d.The lungs

The brain, along with the spinal cord, forms the central nervous system. The brain processes information and directs the body's responses.

Which of the following is a chemical change rather than a physical change?

• a.Ice melting
• b.Chopping wood
• c.Water boiling
• d.Iron rusting✓

A chemical change produces a new substance with different properties. Iron rusting forms iron oxide, whereas melting, boiling, and chopping only change form.

Which macromolecule is made of amino acids and builds body tissues?

• a.Nucleic acid
• b.Carbohydrate
• c.Protein✓
• d.Lipid

Proteins are built from chains of amino acids. They form the structural basis of muscles, enzymes, and many other body tissues.

How many chambers does the human heart have?

• a.Four✓
• b.Two
• c.Three
• d.Five

The human heart has four chambers: two upper atria and two lower ventricles. This structure keeps oxygen-rich and oxygen-poor blood separated.

Which particle in an atom carries a negative electric charge?

• a.Nucleus
• b.Neutron
• c.Electron✓
• d.Proton

Electrons carry a negative charge and occupy orbitals, which are regions of space surrounding the nucleus where an electron is most likely to be found. Protons are positive and neutrons have no charge.