The Biology portion of the HESI A2 exam comprises of 25 questions (8% of total exam):
Topics covered inside of this exam includes:
General Knowledge
- DNA
- Water (H2O)
- Macromolecules
- Metabolism
- The Cell
- Cellular Respiration
- Photosynthesis
- Cellular Reproduction
- Genetics
Biology general knowledge includes understanding organism classifications. You should understand organism kingdoms and their hierarchy. There are five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Each kingdom has certain features that allow an organism to be easily assigned to one of the kingdoms.
Also part of general knowledge is evolution. You should have a good understanding of Charles Darwin’s theory of natural selection and how certain traits help species survive.
1. DNA
Deoxyribonucleic acid is formerly known as (DNA)is a molecule composed of two chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.
The structure of the DNA is depicted as a double helix.
A helix is a curve, and a double helix is two congruent curves connected by horizontal elements. The structure can be compared to a spiral staircase; it is right-handed.
2. Water (H20)
You should have a good understanding of the seven important properties of water: (1) high polarity, (2) hydrogen bonding, (3) cohesiveness, (4) adhesiveness, (5) high specific heat, (6) high latent heat, and (7) high heat of vaporization.
3. Macromolecules
You should have a good understanding of the four basic organic macromolecules: (1) carbohydrates (polysaccharides), (2) nucleic acids, (3) proteins, and (4) lipids and their roles inside of the human body.
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4. Metabolism
Metabolism refers to all the chemical reactions taking place within living organisms which convert nutrients to energy and macromolecules.
Metabolic pathways are a series of reactions where the result of one reaction becomes the substrate for the next. They depend upon enzymes to act as catalysts. You should understand the differences between catabolic reactions and anabolic reactions.
5. The Cell
You should have a good understanding of the following topics: how plant and animal cells function, the 7 parts of the nuclear parts of a eukaryotic cell, the 4 functions of mitochondria, passive and active transport mechanisms and cell theory.
6. Cellular Respiration
Cellular respiration is a series of metabolic reactions that change chemical bonds into energy, which is stored in the form of ATP. Respiration involves a variety of oxidation and reduction reactions, which take place because of the electron transport system that exists within cells.
Four processes form part of cellular respiration: glycolysis, the Krebs cycle, the electron transport chain, and chemiosmosis.
You should have a good understanding of the similarities and differences between the two forms of respiration; aerobic and anaerobic.
7. Photosynthesis
Photosynthesis, the conversion of sunlight into energy in plant cells.
Photosynthesis, a type of cellular respiration, takes place in chloroplasts that use thylakoids, structures in the membrane that contain chemicals that react to light.
The equation that expresses the chemical reaction that takes place in photosynthesis is 6H2O + 6CO2 → C6H12O6 + 6O2.
As can be seen in the expression, six molecules of water and six molecules of carbon dioxide react to form one molecule of sugar and six molecules of oxygen during photosynthesis
8. Cellular Reproduction
The cell cycle is the process of cell reproduction, involving cell growth, duplication of genetic material, and cell division.
Complex organisms with many cells replace the cells that lose their purpose and wear out by using the cell cycle.
While the entire cell cycle in animal cells could last 24 hours, the time needed by different cell types can vary greatly.
For example, human skin cells are constantly reproducing, while other cells rarely divide.
Cells reproduce in two ways, through meiosis and mitosis.
- Mitosis takes place when a “daughter cell” – or exact replica of the parent cell – is produced.
- Meiosis occurs when “daughter cells” have different genetic coding than the parent.
Cell division in organisms allows old, worn out, or damaged cells to grow and be replaced.
9. Genetics
Genetics is a field of biology that studies how traits are passed from parents to their offspring. The passing of traits from parents to offspring is known as heredity, therefore, genetics is the study of heredity.
Gregor Mendel, also known as the father of genetics, discovered the fundamental laws of inheritance through his work on pea plants. He found that genes come in pairs and are inherited as distinct units, one from each parent.
Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. Mendel recognized there was mathematical patterns of inheritance from one generation to the next. Mendel’s Laws of Heredity are usually stated as: (1) the law of segregation and (2) the law of independent assortment and (3) the law of dominance.
- The law of segregation declares that there are two alleles and that one-half the total number of alleles are contributed by each parent organism.
- The law of independent assortment declares that traits are randomly passed on; they are not influenced by other traits. An exception to this is linked traits.
- The law of dominance declares that an organism with alternate forms of a gene will express the form that is dominant.
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