About the MCAT > MCAT Biology
Table of Contents
Prokaryotic Cells are simple organisms that contain no membrane bound organelles. Prokaryotes reproduce solely through asexual reproduction, in which offspring is identical to the single parent. Viruses are also included in this section, and although they are currently not considered true life forms as they cannot produce without a parasitic relationship with a host organism.
See Eukaryotic Cells
Eukaryotic Cells contain a nucleus and other organelles and are surrounded by a cell membrane. The main differentiator between Eukaryotic cells and Prokaryotic cells is the presence of a nucleus, where all of the cell’s DNA is encapsulated within a membrane, within the cell’s cytoplasm.
The nucleus and other organelles are only found in a eukaryotic cell; in prokaryotic cells, the DNA is suspended freely in the cell’s cytoplasm, and no membrane bound organelles exist. In this section, the biological nomenclature and processes of eukaryotic cells will be discussed in depth.
Cellular Organelles perform all of the vital functions of a cell, such as energy creation, DNA replication, toxin and waste removal, etc. Some organelles are unique to only plant cell or only to animal cells. Organelles found in animals are the cell membrane, endoplasmic reticulum (both smooth and rough), the Golgi complex, proteins, lysosomes, centrioles, micro-bodies, cytoskeleton, microfilaments, microtubules, intermediate filaments, and the mitochondria. The organelles of both animal and plant cells are discussed in this section.
Enzymes are biological proteins that serve as a catalysts for various biological processes, such as muscle contraction, digestion, and fat storage to name a few. It is important to note that enzymes are there only to speed up reactions, and will not alter its outcome in any other way.
Enzymes typically do this by lowering the activation energy required for the reaction to occur. Since less energy is required, it is easier to get the ball (the reaction) rolling, so to speak. Everything you may need to know about enzymes and their functions for the MCAT will be covered in this section.
Cellular Respiration consists of many different metabolic actions in which the cells of organisms convert chemical energy from various nutrients, such as fats and carbohydrates, into adenosine triphosphate (ATP), and produce waste products. This process is the basic requirement for cellular function, because when cellular respiration is disrupted, the cell will die if respiration is not restored.
This section describes the energy cycle beginning at the process of photosynthesis to describe how organisms are able to obtain the energy necessary to support life. This section will discuss the various energy containing molecules, ATP and ADP synthesis and processes, NAD+ and FAD synthesis and processes, glycolysis, fermentation, cellular respiration, the Krebs cycle, and the electron transport chain.
See DNA and RNA
DNA and RNA contain the genetic instructions for the coding of proteins that performs the functions of all modern living organisms. It is essential to the life processes of all known complex organisms, because it is so versatile in encoding vast numbers of unique genetic instructions that makes the diversity of Earth’s ecosystems possible. However, in order for DNA to be useful to complex organisms, a process evolved to allow for the replication of complex DNA molecules. In this section, DNA, RNA, replication and transcription will be discussed in depth.
Ribosomes are responsible for protein synthesis. DNA and RNA determine what, how and when something is produced from the ribosome. Translation is a process where the ribosome determines what instructions are being received by a mRNA (messenger RNA) strand using tRNA (translator RNA) fragments. From this information the ribosome creates polypeptide.
Translation is further broken down into three steps, initiation, elongation, and termination, which are discussed in depth in this section. Finally, there are post translation modifications, which are either specifically performed by your body, or are created as a result of an abnormal spontaneous modification, known as a mutation. Ribosomes, translation, and modification will be discussed in depth in this section.
Mitosis is the process by which a cell, after replicating its chromosomes, separates the chromosomes into two separate, identical sets of chromosomes, each in its own nucleus. By this process, the cells are able to produce two new nuclei, which is needed for the next phase, which involves the formation of a new cell.
The process of forming a new cell after mitosis is completed is called cytokinesis, which involves separating a cell into two new cells, and splitting the cytoplasm and all of its organelles roughly equally between the two. Mitosis and all of its phases will be discussed in detail in this section.
Meiosis is a type of cell division that is necessary for the sexual reproduction of Eukaryotes. This type of cell division produces cells called gametes or spores. In many organisms, i.e. plants and animals, gametes are called eggs and sperm. Meiosis differs with normal mitosis in two different aspects.
The first difference is that recombination in meiosis shuffles the two chromosomes in each pair, where one is received from each parent, producing chromosomes with new genetic combinations in every gamete made. In mitosis, chromosomes produced are identical to to those in the parent cell. The second difference is that the chromosome count in meiosis produces four genetically unique cells, each with half the number of chromosomes as the parent. In mitosis, two genetically identical cells are produced, with the same number of chromosomes as the parent cell. The process of Meiosis is described in depth in this section.
Mendelian Genetics is based off the studies of 19th century Austrian Monk Gregor Mendel. His studies essentially denoted a set of laws of inheritance determined through true breeding of peas and other plants at his monastery. True breeding refers to the fact that the offspring have the same traits as the parents.
An example of his work is the Law of Segregation, in which 1) Genes exist in alternate forms called alleles, 2) Organisms must have 2 alleles for each gene, one from each parent, 3) Two alleles segregate during meiosis resulting in gametes with one allele, and 4) If two alleles are different than only one will be fully expressed. This is called dominance and recessiveness. If both alleles are the same then the expression is considered homozygous and if both alleles are different the expression is considered heterozygous. In this section, Mendel’s studies and everything you need to know about genetic inheritance for the MCAT will be discussed in detail.
The Human Body is comprised of many systems that worked symbiotically together in order to maintain homeostasis. These body systems, while having many unique functions also have many commonalities that should be understood in order to be successful on the MCAT. The MCAT covers all of the major human body systems such as:
Body Systems List
When trying to learn the human body systems try to build bridges between the concepts in microbiology also. These topics will often be linked with questions on the MCAT and are more interconnected than they seem at first.
Evolution is the process by which organisms adapt and change to their environment. This process takes many generations of genetic mutations and natural selection to show substantial differences between an organism and its ancestors. Evolution itself is a law, organisms will always change over time, the theory of evolution is a different concept. The processes involved with evolution, evidence supporting evolution, and the theories developed around the law of evolution will be discussed in this section.