ACT Exams- Science - My Exams Help

1.

Passage:

Vitamin C, also known as ascorbic acid, is an essential nutrient involved in the repair of tissue and the enzymatic production of certain neurotransmitters. It is required for the collagen synthesis in animals and plays a protective role against oxidative stress. Most primates and guinea pigs lack the functioning L-gulonolactone oxidase (GULO) enzyme necessary for vitamin C synthesis, so they must obtain it from their diets. However, many other animals are able to synthesize their own vitamin C.

Question:

Based on the information provided, which of the following statements about vitamin C synthesis is true?

A) Humans and other primates can synthesize their own vitamin C through the action of the GULO enzyme.

B) Guinea pigs have the GULO enzyme and do not need to obtain vitamin C from their diet.

C) Animals that can synthesize vitamin C do not require it in their diets.

D) Most mammals besides primates and guinea pigs have a functioning GULO enzyme.

2.

Passage: Mitosis is the process of cell division that results in the production of two daughter cells with the same number and type of chromosomes as the parent nucleus, due to an autonomous process of chromosome duplication. It ensures that each daughter cell inheriting the parental genome during prokaryotic cell division and eukaryotic cell division. The main stages of the cell cycle are interphase (which includes the G1, S, and G2 phases) and the mitotic phase (which includes prophase, prometaphase, metaphase, anaphase and telophase).

Question: Based on the passage, which of the following best describes the purpose of mitosis?

A) To produce buds or spores for asexual reproduction

B) To ensure each daughter cell receives an identical copy of the parental DNA

C) To fuse diploid nuclei and form a zygote during sexual reproduction

D) To break down the nuclear envelope in preparation for meiosis

3.

Passage: Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. Chloroplasts capture light energy from the sun, using carbon dioxide and water to produce oxygen and energy in the form of ATP and NADPH. Chloroplasts contain chlorophyll, which absorbs light and helps drive the light-dependent reactions that convert carbon dioxide and water into simple sugars that cells can use.

Question: Based on the information provided, where do chloroplasts reside?

A) In plant and algal cells only

B) In all types of cells

C) In the cytoplasm of animal cells

D) Only in leaf cells of plants

4.

Passage: Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions that involve breaking down glucose and other food molecules into smaller units, generating a relatively small amount of ATP in the process. Glucose and other food molecules are oxidized to carbon dioxide and water in a set of redox reactions; this releases the chemical energy stored in the bonds of food molecules that is harvested to produce ATP.

Question: Based on the passage, which of the following most accurately describes the purpose of cellular respiration?

A) To convert energy from glucose into a form cells can immediately use to do work

B) To break down carbon-based molecules and release carbon dioxide as a waste product

C) To transfer electrons from reduced coenzymes like NADH to the electron transport chain

D) To produce large amounts of ATP during the Krebs cycle and electron transport chain

5.

Passage: Photosynthesis is the process by which plants, algae and some bacteria use sunlight, water and carbon dioxide to produce oxygen and energy in the form of adenosine triphosphate (ATP) from simple organic molecules like glucose and other carbohydrates. Photosynthesis has two stages: the light-dependent reactions and the light-independent reactions. During the light-dependent reactions, chlorophyll absorbs light energy that is then used to convert carbon dioxide and water into organic compounds like glucose. The light-independent stage involves a carbon fixation reaction where the organic compounds are synthesized using the energy from the light-dependent stage.

Question: Based on the passage, which of the following is not an input required for photosynthesis?

A) Sunlight

B) Carbon dioxide

C) Oxygen

D) Water

6.

Passage: DNA polymerase is a family of enzymes that replicate deoxyribonucleic acid (DNA) in cells. DNA polymerase catalyzes the formation of a backbone alternating with deoxyribose and phosphate into a complementary strand of DNA. It joins nucleotides together in the 5ʹ to 3ʹ direction, using the original DNA strand as a template to direct the assembly of nucleotides into a new strand that is complementary to the original strand. DNA polymerase works in concert with other proteins to proofread and ensure high-fidelity synthesis of the complementary strand during DNA replication.

Question: Based on the passage, which of the following best describes the function of DNA polymerase during DNA replication?

A) To break the bonds between nucleotides in the parent DNA strands

B) To methylate cytosine nucleotides in the newly synthesized strand

C) To proofread and correct any errors made during DNA synthesis

D) To assemble a new DNA strand that is complementary to the parental strand using the original as a template

7.

Passage: Mitochondria are intracellular organelles found in the cells of most eukaryotic organisms. Mitochondria are sometimes described as “cellular power plants” because their main function is to produce adenosine triphosphate (ATP), which is used as the primary “energy currency” of a cell to drive many chemical reactions and physical work. ATP production occurs during cellular respiration, where mitochondria harness chemical energy stored in glucose and other nutrients and release it to fuel biological processes. Mitochondria contain their own circular DNA and bacterial-like ribosomes, remnants of their bacterial ancestry.

Question: Based on the passage, which of the following BEST describes the main role of mitochondria in cells?

A) To package and transport materials like proteins around the cell

B) To contain the genetic material for the entire cell

C) To provide structure and protection to the cell

D) To generate energy through cellular respiration in the form of ATP

8.

Passage: The human body has many homeostatic mechanisms that maintain stable, optimal conditions for physiological functions despite fluctuations in the internal and external environments. One example is thermoregulation, which keeps the body’s core temperature within a narrow range even when surrounding temperatures differ widely. Other examples include regulation of pH, water balance, electrolyte and blood glucose levels. Homeostatic regulation involves negative feedback systems that respond to change and return conditions to normal levels. Sensors monitor conditions and stimulate effectors if levels rise above or fall below normal set points.

Question: Based on the information provided, which of the following statements about homeostasis is true?

A) Homeostatic systems utilize positive feedback to initiate a response to change.

B) Examples include regulation of breathing rate and heart rate.

C) Homeostatic mechanisms aim to maintain conditions far outside the normal range.

D) Negative feedback loops detect deviations from set points and correct them.

9.

Passage: Meiosis is the process that eukaryotic cells undergo to produce gametes like sperm or egg cells with half the normal chromosome number (haploid cells) for sexual reproduction. The main events of meiosis include DNA replication followed by two rounds of nuclear division—meiosis I and meiosis II—without an intervening DNA synthesis phase. During meiosis I, homologous chromosomes pair up and undergo crossing over before separating. This randomized reassortment of genes from both parent organisms. Meiosis II then separates sister chromatids, reducing the number of chromosomes to half before the final haploid gametes are formed.

Question: Based on the passage, which of the following is a key difference between mitosis and meiosis?

A) Meiosis produces four daughter cells while mitosis only produces two.

B) Meiosis involves DNA replication prior to nuclear division while mitosis does not.

C) Meiosis forms haploid gametes and mitosis forms diploid somatic cells.

D) Meiosis undergoes one round of nuclear division and mitosis undergoes two.

10.

Passage: The human brain is a complex organ responsible for coordinating sensory, voluntary, and involuntary functions in the human body. It collects information through the senses and directs motor responses. It regulates vital functions such as breathing and circulation. The brain directs higher brain functions such as thought, emotion, memory, speech, and consciousness. The cerebral hemispheres are the largest part of the brain. They contain regions responsible for memory, language, calculation, spatial perception, and voluntary movement. Lower regions of the brain control fundamental life-support functions and have strong connections with the spinal cord.

Question: Based on the passage, which of the following best describes the primary role of the human brain?

A) To regulate involuntary processes like breathing and digestion

B) To filter sensory information and generate unconscious reflex responses

C) To direct higher cognitive functions and coordinate voluntary movements

D) To store long-term memories and relay signals to the spinal cord