ATI TEAS Version 7 - Science

Correct Answer D. Facilitated diffusion

Explanation of Correct Answer:

Water molecules primarily enter cells through facilitated diffusion via specialized protein channels called aquaporins. Facilitated diffusion is a passive transport mechanism, meaning it does not require energy and moves molecules down their concentration gradient — in this case, from areas of higher water concentration to lower concentration inside the cell.

Why the Other Options Are Incorrect:

A. Electrochemical gradients

These refer to the movement of ions, such as sodium or potassium, driven by charge and concentration differences — not water molecules.

B. Gated channels

These protein channels typically open in response to specific stimuli to allow ions or larger molecules to pass — not usually water, which uses aquaporins instead.

C. Proton pumps

These are active transport mechanisms that move hydrogen ions (H⁺) across membranes using ATP — unrelated to water movement.

Correct Answer A. Diffusion down a concentration gradient

Explanation:

The movement of carbon dioxide from the blood into the alveoli occurs primarily through diffusion down a concentration gradient. Carbon dioxide, produced by cellular metabolism, accumulates in the blood and reaches higher concentrations than in the alveolar air. Due to this difference, carbon dioxide moves passively from an area of higher concentration in the blood to an area of lower concentration in the alveoli, where it can then be exhaled. This passive movement requires no energy and is driven solely by the gradient difference.

Why the Other Options Are Incorrect:

B. Active transport using energy

Active transport requires cellular energy (ATP) to move substances against their concentration gradient. Since carbon dioxide moves down its concentration gradient during gas exchange, active transport is unnecessary and does not occur in this process.

C. Conversion to carbon monoxide

Carbon dioxide is not converted to carbon monoxide in the body. Carbon monoxide is a toxic gas from external sources (like car exhaust) that binds to hemoglobin more effectively than oxygen but plays no role in normal gas exchange.

D. Passive transport using carrier proteins

While some substances use passive transport via carrier proteins, gases like carbon dioxide diffuse directly through the respiratory membrane due to their small size and lipid solubility. Carrier proteins are not involved in this specific gas exchange process.

Correct Answer:

remains unchanged.

Explanation:

In the periodic table, elements in the same group (column) share the same number of valence electrons, which determines their chemical reactivity and bonding behavior. This is why elements within a group often exhibit similar chemical properties. For example, all elements in Group 1 (alkali metals) have one valence electron, regardless of whether they are at the top or bottom of the group. Thus, the valence remains unchanged within a group.

Why Other Options Are Wrong:

increases from top to bottom.

This is incorrect because the number of valence electrons does not increase down a group. Although the number of energy levels (shells) increases, the outermost electron count stays the same within a group.

decreases from top to bottom.

This is false because, again, the number of valence electrons in a group is consistent from top to bottom. The difference lies in the energy levels, not the valence electron number.

changes unpredictably.

This is not true. The periodic table is structured specifically to reflect predictable patterns, especially in group valence electrons. This predictability is the basis for the table’s design and usefulness in chemistry.

Neurons communicate using both electrical and chemical signals. Electrical impulses, called action potentials, travel along the axon of a neuron. When the impulse reaches the synapse, it triggers the release of neurotransmitters, which are chemical messengers that cross the synaptic gap to transmit the signal to the next neuron’s receptors. This dual process ensures precise and efficient neural communication.

Correct Answer:

Photosynthesis

Explanation:

Photosynthesis is the process by which light energy is captured by chlorophyll in plant cells and used to convert carbon dioxide and water into glucose and oxygen. This process stores light energy in the chemical bonds of organic molecules, such as glucose, which can later be used as energy sources by the organism. It is the fundamental method by which energy from sunlight enters the biosphere.

Why Other Options Are Wrong:

Replication

This is incorrect because replication is the process of copying DNA before cell division. It involves duplicating genetic information, not capturing or storing energy in molecules.

Respiration

This is incorrect because respiration, particularly cellular respiration, breaks down organic molecules like glucose to release energy. It is a catabolic process, not one that stores energy.

Transcription

This is incorrect because transcription is the process of synthesizing RNA from DNA. It plays a role in gene expression, not in energy transformation or storage.

The ectoderm is the outermost germ layer formed during early embryonic development and is responsible for giving rise to the nervous system, including the brain, spinal cord, and peripheral nerves. It also forms structures such as the epidermis, hair, nails, and sensory organs. The ectoderm develops into the neural tube, which later differentiates into major components of the central nervous system.

A neutralization reaction occurs when an acid reacts with a base to form a salt and water. This type of reaction balances hydrogen ions (H⁺) from the acid and hydroxide ions (OH⁻) from the base, resulting in a neutral product. For example:
HCl + NaOH → NaCl + H₂O
Here, hydrochloric acid reacts with sodium hydroxide to produce sodium chloride (salt) and water.

The hierarchical system of biological classification, also known as taxonomic ranking, organizes living organisms from the most general to the most specific categories. The correct order is:
Kingdom → Phylum → Class → Order → Family → Genus → Species.
This system helps scientists classify and identify organisms based on shared characteristics and evolutionary relationships. For example, humans are classified as:
Kingdom: Animalia → Phylum: Chordata → Class: Mammalia → Order: Primates → Family: Hominidae → Genus: Homo → Species: sapiens.

When a fluid’s viscosity increases, its internal friction also increases, causing particles to move less freely. This decrease in particle mobility leads to a slower flow rate and greater resistance to motion. For example, honey has a higher viscosity than water, so its particles move more slowly and resist flow.