Question	Answer
What are the two main components of a fat molecule?	The two main components of a fat molecule are a glycerol backbone and three fatty acid tails. Glycerol is known as a small organic molecule with 3 hydroxyl groups (OH) The glycerol backbone than reacts with the carboxyl groups of the fatty acids in dehydration synthesis, and ultimately creates a fat molecule with 3 fatty acid tails bound to the glycerol backbone by ester linkages.
Describe the process of dehydration synthesis in the formation of a fat molecule.	In dehydration synthesis, a fat molecule is created. This is as the hydroxyl group on the glycerol backbone reacts with carboxyl groups of fatty acids, which ultimately creates a fat molecule with 3 fatty acid tails.
How do saturated and unsaturated fatty acids differ in terms of their chemical structure?	Saturated and unsaturated fatty acids differ in their chemical structure. This is seen as saturated fatty acids tend to have as many hydrogen atoms as possible attached to the carbon skeleton. In contrast, unsaturated fatty acids tend to have fewer hydrogens attached to the carbon skeleton.
Explain the significance of cis and trans configurations in unsaturated fatty acids.	Cis and trans configurations in unsaturated fatty acids are significant to the topic of fatty acids as a whole. In a cis configuration, two hydrogens are on the same side, while in trans configuration, they are on opposite sides. It is also seen that cis double bonds create a bend in the fatty acid, which can create consequences for the behavior of fats such as, making it harder for fat molecules to pack tightly, which makes what we now know as commonly called oils.
What is the role of triglycerides in the human body?	Triglycerides play a vital role in the human body, This is seen as triglycerides are usually measured and analyzed during blood work. These triglycerides make up tissue known as adipose tissue, which if there is too much, the body can run out of tissue to store lipids in, so fat cells grow.
Why are omega-3 and omega-6 fatty acids considered essential, and how can they be obtained?	Omega-3 and omega-6 fatty acids are considered essential. This is as they are classified as essential fatty acids, and ultimately must be obtained from a person’s diet (our body cannot naturally produce it). They are known as precursors for the synthesis of many biological molecules, and can reduce the risk of sudden death from heart attacks, and lower blood pressure. These can be obtained through eating different foods that are rich in Omega-3 & 6 such as, salmon and chia seeds.
Describe the structure and function of phospholipids in cell membranes.	The structure of phospholipids in cell membranes is as listed, composed of fatty acid chains that are attached to the backbone of glycerol, have 2 fatty acid tails, and the 3rd carbon of the glycerol backbone is occupied by a phosphate group. Phospholipids may have different modifiers on the phosphate group: Choline, serine. Phospholipids act as a barrier between the cells internal and external environment, which allows the cell to regulate what passes through the membrane
How do micelles form, and why is this formation energetically favorable?	Micelles form when a drop of phospholipids are placed in water. When the hydrophilic phosphate heads face the outside, and the fatty acids face the interior, it creates micelles. This is energetically favored, as the unfavorable interactions between hydrophobic tails and water are minimized.
What structural feature distinguishes steroids from other lipids, and what is the role of cholesterol in the body?	Steroids tend to be identified by their structure of four fused rings. This is as they do not resemble other lipids, which may have long hydrocarbon chains.
Discuss the impact of trans fats on the physical properties of fats and their implications for human health.	Trans fats impact physical properties of fats as they can become more solid at room temperature due to their structure. This may lead to detrimental health effects such as, increased risk of heart disease and stroke when they are consumed in large quantities. They can also increase cholesterol levels.
What is the primary role of membrane proteins in biological membranes?	Membrane proteins play an important & necessary role in biological membranes. Membrane proteins give each type of membrane in the cell its characteristic functional properties. Different membrane proteins are often associated with membranes in different ways. Some extend through the lipid bilayer (part of their mass on either side), while others do not. Membrane proteins are located in cytosol and tend to be associated with the cytosolic monolayer of the lipid bilayer. Others are entirely exposed at the external cell surface, and are attached by covalent linkage. Overall, their primary function is to facilitate many different cellular functions and processes such as acting as receptors for signaling, and allowing cell-to-cell communication.
Describe the difference in protein composition between the myelin membrane and the membranes involved in ATP production.	These proteins are highly variable, meaning they can likely be changed often. More specifically, in the myelin membrane (electrical insulation for nerve cell axons), 25% of the membrane mass is protein, and in membranes which are involved in ATP production (inner mitochondrial membrane), 75% of the weight is protein. Because lipid molecules are very small compared to protein molecules, there are always more lipid molecules in membranes. Only transmembrane proteins can function on both sides of the bilayer or transport molecules across the membrane. Proteins that function on one side of the bilayer, are often associated with the protein domain on that side.
Explain how transmembrane proteins interact with the lipid bilayer.	Transmembrane proteins interact with the lipid bilayer uniquely. Transmembrane proteins tend to function on both sides of the bilayer, and are able to transport molecules directly across the membrane. A specific type of transmembrane protein is a cell-surface receptor, mainly as they bind signal molecules in the extracellular space, and generate different signals on the opposite side of the membrane. These proteins have unique orientation, which reflects the asymmetric manner that it is synthesized in. In single–pass transmembrane proteins, polypeptide crosses only once in the bilayer, while in multipass transmembrane proteins the polypeptide chain crosses multiple times. Because they are notoriously difficult to crystallize, few have been studied in their entirety, mainly by x-ray crystallography, which reveals the amino acid sequences of transmembrane proteins.
What are the 3 types of transports, and explain how they differ in the transport inside the cell?	Cells rely on passive transport, facilitated transport, and active transport to move substances across their membranes. Passive transport does not require energy because molecules move down their concentration gradient, naturally diffusing through the cell membrane or using water channels in osmosis. Facilitated transport, a type of passive transport, helps larger or polar molecules cross the membrane with the assistance of protein carriers or channels, allowing substances like glucose and ions to enter the cell efficiently. Active transport, in contrast, requires energy in the form of ATP to move molecules against their concentration gradient, enabling vital processes such as the sodium-potassium pump that maintains cellular function. Each of these transport mechanisms plays a crucial role in ensuring cells receive nutrients, expel waste, and communicate effectively within their environment
define the following terms: anabolic, catabolic, metabolism, cellular respiration and photosynthesis.	Anabolic is a type of pathway that is categorized by its effect. This means that a smaller molecule is “built up” rather than “broken down”. These pathways tend to need an input of energy to react. This energy is important and essential for the life of the cell, as these pathways use ATP to complete their roles. (Synthesis of proteins from amino acids) Catabolic is another type of pathway that is also categorized by its effect. This means that more complex molecules are “broken down” rather than “built up”. These pathways usually release energy when a reaction occurs, and tend to harvest remaining energy to do work for the cell. (ATP Synthesis) Metabolism is defined as the collective whole of chemical reactions that take place within the cell that can be used to create and conserve energy, which is used as a tool for growth, repair, and other functions within the cell such as glycolysis, which breaks down glucose into pyruvate in the cytoplasm. Cellular respiration is defined as a chemical reaction in which the cells get energy from the cell, as the glucose molecule is gradually broken down. When glucose is broken down, energy is released and captured in the form of ATP (energy storage source). Once this ATP is created, it is used by cells for chemical reactions. Photosynthesis is a chemical reaction in which glucose is made in plants, algae, and bacteria. More specifically this reaction uses energy from sunlight to convert CO2 gas into sugars. This energy can also be stored and used for later use.
Briefly explain the difference between substrate-level phosphorylation and oxidative phosphorylation.	Substrate-level phosphorylation and oxidative phosphorylation are two different ways cells produce ATP, the energy carrier molecule. Substrate-level phosphorylation occurs directly in glycolysis and the Krebs cycle, where a phosphate group is transferred from a high-energy substrate to ADP, forming ATP without the need for an electron transport chain or oxygen. In contrast, oxidative phosphorylation takes place in the mitochondria and involves the electron transport chain, where electrons are passed through a series of proteins, ultimately driving ATP synthesis through chemiosmosis. This process is highly efficient, producing far more ATP than substrate-level phosphorylation, and requires oxygen as the final electron acceptor in aerobic respiration
What is gluconeogenesis?	Gluconeogenesis is defined as a group of metabolic reactions in cytosol and mitochondria that help maintain the blood glucose level constant through a state of fasting or starvation. Many reactions that are regulated both locally and globally are insulin, glucagon, and cortisol. The balance between the hormones help regulate the rate of gluconeogenesis. Some organs that are affected by gluconeogenesis are the liver, kidney, and organs that supply blood glucose to various tissues. The tissues tend to have various mechanisms to generate glucose, and ultimately maintain energy levels for proper function. Ultimately pyruvate is produced as a key byproduct of glycolysis.
Explain the purpose of the citric acid cycle. In your discussion include why the citric acid cycle is considered an aerobic process although oxygen is not consumed during the process.	The Citric Acid Cycle or what is commonly referred to as the Krebs Cycle, is an oxidative process in which Acetyl-CoA is turned into Carbon Dioxide, and is overall a precursor to other biosynthetic reactions. This cycle takes place in the mitochondrial matrix and transfers energy from ester bonds and conserves it into NADH. This cycle consists of 8 steps, all of which are precursors to one another. This cycle is crucial as it is described as the “central hub” in cellular respiration, and while generating energy, provides precursors for other important metabolic pathways such as the electron transport chain While it can be said that the citric acid cycle does not consume oxygen, it is referred to as an aerobic process. This is as NADH and FADH2 transfer electrons to an oxygen-dependent pathway. This means that it requires oxygen to occur efficiently, as well as to regenerate coenzymes needed to continue the cycle (NAD+, GTP, or ATP). These coenzymes are needed as they are carriers for electrons and protons, and facilitate the oxidation/reduction reactions that occur within the citric acid cycle.
Write a brief 2-3 paragraph description of the electron transport chain. Include where it is located, what the main components of the ETC are and how it utilizes the products of the Krebs cycle as a substrate.	The electron transport chain is a series of 4 complexes, all of which create an electrochemical gradient that ultimately forms ATP through redox reactions. This process occurs within the mitochondria, and creates energy used to form carbohydrates from breaking down organic molecules and reacting to light. The ETC is also seen as a collection of proteins all bound to the inner mitochondrial membrane, and is paired alongside chemiosmosis, in which the proton gradient formed by the ETC creates mass amounts of ATP by using the protein ATP-synthase. The 4 main complexes are known as ubiquinone oxidoreductase, succinate dehydrogenase, coenzyme Q, cytochrome c reductase, and cytochrome c oxidase. The Krebs Cycle ultimately uses oxaloacetate as a key substrate. Oxaloacetate is a critical component of producing ATP, and is constantly regenerated in the citric acid cycle and electron transport chain. Another key substrate is Acetyl-CoA, which is produced from pyruvate and is known as the starting point of the Krebs Cycle. Another key substrate is NAD+ , which is a vital electron carrier acting as a coenzyme, and accepts electrons during oxidation and becoming NADH & FADH2.
Compare and contrast the exogenous and endogenous lipid pathways	Exogenous Lipid Pathways can be defined as the process by which dietary lipids such as triglycerides and cholesterol are transported from the intestines to other tissues, to provide for energy and storage. These pathways include lipids derived from diet, meaning these pathways provide transport for foods that we eat and provide from our diets. The process starts off with dietary triglycerides being absorbed into the small intestine. After this, lipids are packaged into chylomicrons, which are the smallest lipoproteins absorbed by diets. After this, chylomicrons travel throughout the bloodstream, and when in tissues, they release triglycerides for both energy and storage. Endogenous Lipid Pathways can be defined as the process by which the body transports and overall metabolizes lipids synthesized within the body, primarily through the liver, for energy storage and utilization. These pathways include lipids produced by the liver such as triglycerides and cholesterol esters, which are lipids that form when fatty acids join the hydroxyl group of cholesterol. The process starts off with the liver synthesizing cholesterol and triglycerides. After this, the lipids are packed in VLDL particles (VLDL means very low density lipoprotein). Then VLDL particles flow throughout the bloodstream, and the remnants are processed into IDL particles (IDL means intermediate-density lipoprotein) and ultimately form into LDL particles (LDL means low density lipoprotein), and then taken by the tissues and the liver.
What is the effect of a ketogenic diet on the brain and how can it help improve brain function in neurodegenerative diseases?	Ketogenic bodies are defined as alternative energy sources for the brain and other tissues when glucose is scarce. This utilization seems to depend on the concentration of ketones in the body, so in specific cases such as ketogenic diets, changes in the brain are facilitated in metabolism. Most of the energy that is created from this oxidation is used to support the maintenance of ion gradients, which are crucial for the creation of potential energy to drive other cellular processes such as active and passive transport. From this it can be said that a continuous supply of energy is needed to maintain brain cellular functions. When the brain is restricted from glucose production, it can rely on other substrates to metabolize. Due to increased interest in ketogenic diets, treatments such as ketogenic bodies have been created as a potential therapeutic practice to cure disorders such as cancer, diabetes, cardiovascular disease, and neurodegeneration. Different studies of Alzheimers, Parkinsons, ALS, and huntingston have shown that hypometabolism, which is low metabolic activity, is seen in affected brain regions. While fasting, free fatty acids are brought from adipocytes to the liver, where ketone bodies are synthesized. A high level of acetyl-CoA is essential for ketogenesis, and is obtained through high level supplementation of free fatty acids, which could lead to the derivation of acetyl-CoA from the TCA cycle for ATP generation. Ketogenesis requires the action of mitochondrial Acetoacetyl-CoA thiolase, mitochondrial 3-hydroxy-3-methylglutaryl-CoA, and HMG-CoA lyase, to form the ketone body acetoacetate. Ketogenic diets increase circulation of ketone bodies, and overall mimics the action of fasting due to high consumption of lipids and low intake of carbohydrates. Many approaches have been made to increase amounts of ketone bodies in elderly individuals that affect cognition, which include acute interventions of BHB infusion or long-term treatments with continued MCFA supplementation approach to achieve ketonemia.

Biochemistry Final FRQs