ATI TEAS Version 7 Science Comprehensive Study Guide

Cell Biology and Biochemistry

A totipotent cell is characterized by its unique ability to develop into any kind of cell within an organism. This level of potency allows the cell the greatest flexibility in differentiation compared to pluripotent or multipotent cells. In the context of cellular protection and signaling, the myelin sheath serves a critical role for nerve cells by providing insulation. This fatty layer accelerates the transmission of electrical impulses along the axon.

Energy production and photosynthesis involve specialized membranes with analogous functions. The mitochondrial inner membrane, which is the site of the electron transport chain in cellular respiration, carries out a function similar to the thylakoid membrane of chloroplasts found in plant cells during photosynthesis. Structurally, both prokaryotic and eukaryotic cells share certain fundamental components, most notably the cell membrane, which acts as a selective barrier for the cell.

Enzymes are a specific class of biological molecules categorized as proteins. These molecules act as catalysts in chemical reactions, meaning they allow a reaction to be completed in a shorter amount of time without being consumed in the process. The individual monomers of an enzyme macromolecule are held together by peptide bonds, which are the covalent bonds formed between amino acids. Functional genetic information that describes the characteristics of an organism is housed within the nuclei of eukaryotic cells.

In the immune system, specific molecules known as perforins are responsible for destroying target cells by creating holes in their cell membranes. Other molecules found in blood plasma include fibrinogens, which are essential proteins for the blood-clotting process. In contrast, lymphocytes, monocytes, and platelets are cellular or cell-fragment components of blood rather than plasma proteins.

Human Anatomy and Physiology

The human body is organized in a hierarchical structure from simple to complex, proceeding from atoms to cells, then to tissues, and finally to organs. Within the skeletal system, bones serve multiple vital functions, including the storage of minerals such as calcium and phosphorus. The tibia and fibula are specific bones located in the crural region of the body, which corresponds to the lower leg.

In the integumentary system, the epidermis is the outermost layer of the skin and is notable because it lacks blood vessels. Sweat glands in the skin excrete various substances; urea is specifically excreted in response to the breakdown of proteins and the subsequent formation of ammonia. Additionally, apocrine glands are components of the integumentary system known to secrete pheromones. Protective secretions also include sebum and lysozymes.

The nervous system utilizes different types of neurons for signaling. An efferent neuron, specifically a motor neuron, is responsible for releasing neurotransmitters that stimulate a muscle cell to contract. The process of repolarization in a neuron, which returns the cell to its resting potential, occurs through the opening of potassium channels, allowing potassium ions ($K^+$) to leave the neuron.

The cardiovascular and respiratory systems work in tandem to maintain homeostasis. During the cardiac cycle, the term diastole describes the relaxation of the chambers of the heart. The thoracic cavity houses the heart and lungs, making these organs the most at risk during severe blunt trauma to that region. In the respiratory system, the exchange of oxygen ($O_2$) and carbon dioxide ($CO_2$) occurs in the alveoli. This movement of carbon dioxide from the blood into the alveoli is primarily driven by diffusion down a concentration gradient. Conditions like emphysema, which involve damage to the alveoli from toxins or pollutants, severely hinder the body's ability to perform this gas exchange.

The digestive and excretory systems manage nutrients and waste. Both digestion and absorption take place in the small intestine. Specifically, lipids absorbed in the small intestine first enter the lacteal vessels of the lymphatic system. In the reproductive system, ovulation is the specific process in which an ovarian follicle matures and releases a reproductive egg. For waste management, the kidney is the primary organ responsible for filtering excess solutes from the blood. Exocrine glands, such as the parotid gland, secrete substances into ducts, whereas endocrine glands like the pituitary, pineal, and parathyroid glands secrete hormones directly into the bloodstream.

Genetics and Heredity

Genetic mutations can have various impacts depending on where they occur. Cancer is defined as a genetic mutation that results in the uncontrolled division of a single cell within the body. When considering inheritance, a mutation can only be passed from a mother to her offspring if it occurs in a germ cell. Mutations in somatic cells, stem cells, or white blood cells are not typically heritable.

DNA structure follows strict base-pairing rules where Adenine ($A$) pairs with Thymine ($T$) and Cytosine ($C$) pairs with Guanine ($G$). If a portion of a DNA strand reads $5'\,AGCTAGCGT\,3'$, the complementary strand will read $3'\,TCGATCGCA\,5'$. In Mendelian genetics, an organism with an unknown genotype crossed with a recessive organism ($aa$) that produces both heterozygous ($Aa$) and homozygous recessive ($aa$) offspring indicates that the unknown genotype was heterozygous ($Aa$).

Chemical Principles and Matter

The transition of matter between phases involves changes in particle behavior. As a solid turns into a liquid, the particles become less ordered. The triple point of a substance refers to the specific temperature and pressure at which the substance exists simultaneously in solid, liquid, and gas phases.

Chemical reactions often involve the movement of electrons. In an oxidation reaction, there is a removal of electrons from a substance. Ionic charges are determined by the balance of protons and electrons; for instance, a chloride ion ($Cl^-$) carries a negative charge because it has gained an electron.

The $pH$ scale measures the acidity or alkalinity of a substance and is logarithmic. A substance with a $pH\,3$ is $10$ times more acidic than a substance with a $pH\,4$. When comparing the hydrogen-ion concentration ($H^+$) of a $pH\,4$ solution to a $pH\,9$ solution, the $pH\,4$ solution is $10^5$ or $100,000$ times stronger. To manage fluctuations in blood $pH$, the body uses buffers; carbonic acid is the substance responsible for donating $H^+$ ions to act as a buffer when blood $pH$ rises.

Soap acts as an emulsifier, which is useful for cleaning because of its dual polar and nonpolar nature. This allows soap to bond with both oil (nonpolar) and water (polar), facilitating the removal of dirt.

Scientific Inquiry and Laboratory Methodology

Accurate scientific measurement requires specific tools. To measure the density of irregular solids, one needs a weighing balance for mass and a graduated cylinder with water to determine volume via displacement. A spectrophotometer is used to measure the turbidity of a liquid by calculating the transmission of light through a sample.

In scientific research, the validity of data depends on methodology. If a researcher excludes large birds from a study on wing strength due to equipment limitations (such as having only a small net), the data must be rejected because it is biased by the methodology. Furthermore, a correlation between two processes (Process A and Process B) does not indicate a causal relationship between them; it simply shows they vary together.

The scientific method relies on the principle that experiments cannot validate hypotheses, only falsify them. This means that a hypothesis that has not been falsified remains provisional. When new evidence emerges, such as the discovery that parasitic worm infestations might reduce the severity of certain autoimmune disorders, existing hypotheses must be modified to reflect these findings. Additionally, repeating published work is a valuable scientific endeavor because it provides independent confirmation of results.

Environmental and historical factors can affect the preservation of organisms. For example, a body found at high altitude in the Alps may be preserved for over $5,300$ years if it was frozen in cold temperatures shortly after death and remained frozen until discovery. In population ecology, a population that has leveled off on a growth curve is said to have reached its carrying capacity. Small changes in falling objects, such as time of fall differences between objects of the same mass ($5.0\,g$), suggest that factors like air resistance significantly impact the results.