HESI A2 Biology Study Guide ALL SOLUTION 100% CORRECT AID GRADE A+

HESI A2 Biology Study Guide Cellular respiration Cellular respiration is the process inside of cells that converts nutrients (such as sugars, amino acids, and fatty acids) into ATP (adenosine triphosphate), which is used throughout the organism for energy. Large molecules are broken into smaller molecules, which releases both energy and waste. Aerobic respiration occurs in the presence of Oxygen and has four main stages: • Glycolysis: Larger sugar molecule is broken down into 2 smaller sugar molecules in the cytoplasm. Net gain of 2 ATP and 2 NADH • Formation of Acetyl CoA: Pyruvate undergoes oxidative decarboxylation to form Acetyl coenzyme A. 1 CO2 is released as waste. Net gain of 2 NADH. • Citric acid cycle: also known as Krebs cycle. The 2 small sugar molecules produced during glycolysis are oxidized forming new products. Gain of 2 ATP, 6 NADH, 2 FADH2. • Electron transport chain: redox reaction involving the electrons removed during glycolysis and the Krebs cycle. Protons are pumped across the mitochondrial membrane to form a gradient, which drives the synthesis of 34 ATP. Anaerobic respiration is a type of cellular respiration which occurs when oxygen is not present. This process is most commonly performed by bacteria and Achaea. These organisms use this process to obtain energy because they live in environments with low oxygen levels. Example: Achaea called methanogens use carbon dioxide to accept electrons. Methanogens can be found in soil and the digestive systems of animals called ruminants, which includes cows and sheep. Anaerobic respiration, similar to aerobic cellular respiration, uses electrons from the fuel molecules to pass through the electron transport chain, which drives ATP synthesis. The electron transport chain moves electrons to create a proton gradient that allows for the synthesis of ATP. Electron transport chains are used for extracting energy. This can happen in plants, where the energy from the sunlight is used to create glucose and oxygen through photosynthesis in the chloroplast. Eukaryotes perform this process in the mitochondria. Fermentation is another type of cellular respiration which occurs in the absence of Oxygen. Organisms capable of fermentation include prokaryotes, yeast, and multicellular organisms such as humans. Feature Aerobic Respiration Anaerobic Respiration Oxygen requirement Yes, always No, never Waste products Carbon dioxide and water Carbon dioxide and ethanol Efficiency in releasing energy from glucose Very efficient (most of the energy is released from glucose) Less efficient (some energy locked in ethanol is not released) Some energy released as heat Yes Yes, but less than that for aerobic respiration Antibiotics Antibiotics are a kind of medicine used to treat bacterial infections. Not all bacteria are bad or unhealthy. Humans and other animals actually have a healthy ecosystem of bacteria, called normal flora. These are the good kind of bacteria. Pathogenic bacteria are the type which can cause infection. Some bacteria will cause infection no matter where they are, but others are safe in some areas of the body, but become infectious when they wander to a new location in the body. An example of this is if the bacteria in the gut, or intestines, were to try and live in the bladder or another organ. This is what happens in case of a urinary tract infection. The body’s immune system must try to fight and destroy the invading bacteria. Antibiotics are chemicals that enter and stick to certain parts of the bacterial cell. The parts where the antibiotics can attach can be the proteins/sugars in the bacterial cell wall or the important enzymes that make new bacterial DNA or proteins. This act of blocking these parts interferes with the bacteria’s ability to survive and multiply. If the correct antibiotic is used, the bacteria will stop growing or die. Without antibiotics, bacteria can grow and multiply, especially if the immune system cannot battle the bacteria. If enough antibiotic is present, the bacterial cell is crippled and stops growing, known as bacteriostatic, or it simply dies, known as the bactericidal effect. Antibiotics do not affect viruses, fungi or parasites as they bind only to bacterial cell targets. Some bacteria have the ability to become antibiotic resistant. This happens when bacteria have overexposure to antibiotics. The bacteria no longer are affected by the antibiotic because it undergoes mutations. Cells and tissues The basic building block of the body is the cell. Cells can perform a wide variety of functions, depending on the specialized type of cell that it is. Every type of cell plays a vital role in growth, development, and maintenance of the body. Cells from all organisms, ranging from humans to plants to bacteria, share certain characteristics. There are two categories that cells fall into: prokaryotic and eukaryotic. Prokaryotic cells are single-celled organisms from the domains Bacteria and Archaea. “Pro-” means before and “kary-” means nucleus, hence prokaryotic cells lack a nucleus and other membrane-bound organelles. Eukaryotes are made of two or more cells. “Eu-” means true, which means that eukaryotic cells have a nucleus. All types of cells share four key components: plasma membrane, cytoplasm, DNA and ribosomes. Prokaryotic cells have DNA, but it is not housed in a nucleus. The majority of the DNA in prokaryotic cells is found in a central region of the cell called the nucleoid. Bacteria are a specific type of prokaryotic cell. Most bacteria are surrounded by a rigid cell wall, which provides an extra layer of protection, helps the cell maintain its shape and prevent dehydration. Many bacteria have an outermost capsule that is sticky and helps the cell attach to its surroundings. Some bacteria also have a flagellum. It is a whip-like structure that acts like a motor to help the bacteria to move. Fimbriae are hair-like structures that are used to attach to other surfaces or host cells. Sometimes bacteria have pili, which allows the cell to transfer DNA to other bacteria or helps with locomotion (movement). Eukaryotic cells are significantly more complex compared to prokaryotic cells. They contain a variety of different compartments that have specialized functions, and are separated by layers of membrane. This organization allows each compartment to maintain its respective conditions and do what it needs to carry out its job. These compartments are called organelles. Unlike prokaryotic cells, eukaryotic cells have a nucleus, membrane-bound organelles, and multiple linear chromosomes. Eukaryotic cells have an array of organelles that are important for energy balance, metabolism, and gene expression. Difference between plant and animal cells: Plants Animals Cellulose cell wall surrounds the cell membrane Cell wall is absent in animal cells Plastids are present – especially a green pigment called chlorophyll Chlorophyll is absent in animal cells Large vacuoles containing cell sap are present in plant cells Vacuoles are usually absent Most plants do not exhibit movement of locomotion Most animals exhibit movement of locomotion Keep growing throughout their life and are localized in the apical meristem Growth stops after maturation but body cells are replaced periodically. Growth is uniform and proportionate. Manufacture their own food by photosynthesis Cannot make their own food. They depend directly or indirectly in plants for their food Sense organs and nervous system absent Well-developed nervous system Cells make up tissues. Tissues make up organs. Multiple organs make up organ systems, which make up organisms. There are four basic types of tissue: epithelial, connective, muscle, and nervous. Types of cells in tissues: Cells Functions Muscle cells These are usually cylindrical or spindle-shaped. They cause some parts of the body to move by contracting. Epithelial cells They form a layer and protect the cells below them from injury. Red blood cells These cells which are shaped like disco do not have nucleus. They bring oxygen to different parts of the body. White blood cells These cells have a nucleus. They can change their shape. They kill or engulf microorganisms such as bacteria which enter the blood stream. Nerve cells These cells are very long. They carry information (impulse) from one part of the body to another. Sperm This cell has a long tail which helps it to move about. It can unite with an egg cell (ovum) to form a baby. Ovum (egg cell) This is the largest cell in woman’s body. It does not move on its own. It develops into a baby if its united with a sperm. Epithelial tissue consists of tightly packed layers of cells that cover surfaces and line body cavities. This includes skin and intestine lining. Since these cells are tightly packed, they act as barriers to the movement of fluids and harmful invaders. Epithelial cells are special because they are polarized. This means that they have a top and bottom side. The top side is called the apical side and it faces the inside of the cavity or the outside of a structure and is usually exposed to fluid or air. The bottom side is called the basal side. This faces underlying cells. The diagram to the right shows intestinal cells. Connective tissue consists of cells suspended in an extracellular matrix. This matrix is typically made up of protein fibers like collagen and fibrin in a solid, liquid, or jelly like substances. Connective tissue supports and connects other tissues. Loose connective tissue is the most common type and supports organs and blood vessels. Dense, or fibrous, connective tissue makes up tendons and ligaments to connect muscles and bones. Muscle tissue keeps the body upright and allows for movement. Skeletal muscle makes up the muscles of movement and contract and relax voluntarily. Smooth muscle tissue is found in organs, like the stomach and intestines. This muscle works involuntarily. Lastly, cardiac muscle is found in the heart and allows it to beat. Nervous tissue senses internal and external cues, or stimuli, and processes and transmits information. This type of tissue is found in the spinal cord and throughout the body as neurons. Cellular membranes Both prokaryotic and eukaryotic cells have a plasma membrane. This type of membrane is a double layer of lipids that separates the cell’s interior from the outside environment. This double layer is called a phospholipid bilayer. A phospholipid is made of a hydrophilic (water-loving) phosphate head and two hydrophobic (water-fearing) fatty acid tails. The phospholipids arrange themselves, as shown below. Organelles Organelle Type of cell where it Function is found Cell wall Plant cell only Protect and support the cell Allow oxygen and water to pass through Cell membrane Plant and animal cells Controls what comes in and out of the cell Nucleus Plant and animal cells Controls the cell activities Houses DNA Cytoplasm Plant and animal cells Home to the cell’s organelles Mitochondria Plant and animal cells Breaks down sugar molecules to create energy Endoplasmic reticulum Plant and animal cells Carries protein and other materials from one part of the cell to another Ribosomes Plant and animal cells Produces proteins Golgi bodies Plant and animal cells Receives proteins and other materials from the endoplasmic reticulum and packages them to be redistributed Chloroplasts Plant cell only Captures energy from sunlight and uses it to produce food for cells Vacuoles Plant and animal cells Storage area for cells Lysosomes Plant cell: uncommon Animal cell: common Use chemicals to break down food particles into smaller ones Breaks down old cells Cell cycle DNA replication, mitosis, and cytokinesis are the main events of the diploid cell cycle. The cell cycle for somatic cells is different than the cell cycle for gametes. Somatic cells are diploid (contain two homologous chromosomes) and go through mitosis, whereas gametes are haploid (contains only a single set of unpaired chromosomes) and go through meiosis. During DNA replication of somatic cells, the two strands of the DNA double helix are separated. Each strand serves as a template for a new strand to be created. DNA replication takes place during interphase – the preparatory phase for mitosis. There are three stages of interphase: • Gap1: normal cellular function with increased protein synthesis. The cell nearly doubles in size. • Synthesis: the cell duplicates its DNA. Initiator proteins locate the origin of replication on the parent DNA strands. The double helix is “unzipped,” the enzyme primase adds an RNA primer, and the enzyme DNA polymerase elongates the chain. Elongation is terminated when a specific termination sequence is reached. • Gap 2: cell grows and prepares for division. After DNA replication has taken place, mitosis can begin. Mitosis describes how replicated chromosomes are separated into two new nuclei – how the mother cell is divided into two genetically identical daughter cells. There are six phases of mitosis, below: • Prophase: the chromosomes condense • Prometaphase: the nuclear envelope disintegrates and microtubules enter the nucleus • Metaphase: the microtubules attach to the center of each chromosome and start to pull each chromosome to opposite ends of the cell • Anaphase: The proteins that bind chromatids are cleaved and the two daughter chromosomes are fully pulled to opposite ends of the cell • Telophase: events that occurred during prophase and prometaphase are reversed – the chromosomes relax again and the nuclear envelope is reformed. Cytokinesis begins after mitosis. The cell is pinched into two newly formed daughter cells, each containing a complete set of chromosomes. Cytokinesis is the final stage of cell division. It is the division of cytoplasm to form two new cells. Cytokinesis begins as mitosis is ending.