Biology Chapter on Biomolecules and Metabolism

Glycogen is the primary storage form of carbohydrates in animals. It is a branched polymer of glucose molecules, and it is stored in the liver and muscles.

Ribose is a five-carbon sugar that is a component of RNA. It differs from deoxyribose, found in DNA, by having an extra hydroxyl group on the 2' carbon.

Lactose is a disaccharide composed of glucose and galactose. It is commonly found in milk.

Amylose is a polysaccharide composed of straight chains of glucose molecules linked by α-1,4-glycosidic bonds. It is a component of starch and provides energy storage.

Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources, like pyruvate, lactate, and amino acids. It occurs mainly in the liver and is essential during fasting or starvation.

Fructose is a monosaccharide found in fruits, honey, and high fructose corn syrup. It's also a component of sucrose, a disaccharide.

Peptide bonds are the covalent bonds that link amino acids together to form a polypeptide chain. They are formed between the carboxyl group of one amino acid and the amino group of the next.

The tertiary structure of a protein is determined by the interactions between the R-groups (side chains) of the amino acids. These interactions include hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.

Haemoglobin is a protein with quaternary structure. It consists of four polypeptide chains, each with its own tertiary structure, assembled into a functional unit. This structure allows haemoglobin to bind oxygen efficiently.

Cysteine is an amino acid with a sulfhydryl group (-SH) in its side chain. This group can form disulfide bridges, which are important for protein structure.

Enzymes are primarily made of proteins. They act as catalysts, speeding up biochemical reactions without being consumed in the process. They are highly specific for their substrates and play essential roles in all biological processes.

The molecule shown is not an amino acid because it lacks a carboxyl group (COOH) or an amino group (NH2). Both functional groups are crucial for amino acid classification.

Phospholipids are a class of lipids that are major components of biological membranes. They have a hydrophilic head (containing a phosphate group) and two hydrophobic tails (containing fatty acid chains).

Hydrolysis is the process of breaking down triglycerides into their component parts, glycerol, and fatty acids, using water. It is the reverse of condensation.

A fatty acid with one double bond is monounsaturated. It has one point of unsaturation in its hydrocarbon chain.

Chylomicrons are lipoprotein particles that transport lipids, primarily triglycerides, from the small intestine to other tissues. They are essential for lipid absorption and distribution.

Lipase is a type of enzyme that breaks down triglycerides into fatty acids and glycerol. It is found in the pancreas, small intestine, and adipose tissue.

Uracil is a nitrogenous base found in RNA, but not DNA. It pairs with adenine in RNA.

DNA contains deoxyribose, a five-carbon sugar that is similar to ribose but lacks a hydroxyl group on the 2' carbon.

Transcription is the process of converting DNA into messenger RNA (mRNA). It occurs in the nucleus of eukaryotic cells and is the first step in gene expression.

A nucleotide consists of three parts: a sugar (either ribose or deoxyribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil).

During glycolysis, glucose is broken down into two molecules of pyruvate. This process occurs in the cytosol of cells and generates a small amount of ATP.

The electron transport chain is the final stage of cellular respiration, and it produces the most ATP. The process involves the transfer of electrons through a series of protein complexes, generating a proton gradient that drives ATP synthesis.

The urea cycle occurs primarily in the liver. Its main function is to convert toxic ammonia, a byproduct of amino acid metabolism, into urea for excretion through urine.

Beta-oxidation is the process by which fatty acids are broken down into acetyl-CoA units. It occurs in the mitochondria and generates energy in the form of ATP.

Carnitine is a molecule that transports long-chain fatty acids into mitochondria. It is essential for the process of beta-oxidation and fatty acid metabolism.

Enzymes increase the rate of biochemical reactions by lowering the activation energy required for the reaction to proceed. They do this by providing an alternative pathway for the reaction.

ATP is primarily produced in the mitochondria. This organelle is often referred to as the 'powerhouse of the cell', as it is where the majority of ATP synthesis occurs through oxidative phosphorylation.

Water is generated during the electron transport chain as the final electron acceptor, oxygen, picks up electrons and reacts with protons to form water.

Competitive inhibitors bind to the active site of an enzyme, competing with the substrate for binding. They reduce the enzyme's activity by preventing the substrate from binding.

The correct description of the events labelled 1-4 is A) Protons move across the cristae into the intermembrane space, Protons move across the cristae into the intermembrane space, Protons are pumped through ATP synthase, ADP is phosphorylated.

Glucose is the primary substrate for glycolysis. It enters the glycolytic pathway and is broken down into pyruvate, generating a small amount of ATP.

Phosphofructokinase (PFK-1), particularly its isoform PFK-1, is the main regulatory enzyme of the glycolysis pathway. It catalyzes the irreversible phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate.

Phosphofructokinase-1 (PFK-1) is the main regulatory enzyme of the glycolysis pathway. It catalyzes the irreversible phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate.

In anaerobic conditions, pyruvate is converted to lactate in human cells. This process is called lactic acid fermentation and allows glycolysis to continue producing ATP despite the absence of oxygen.

The primary purpose of the citric acid cycle is to generate NADH and FADH2, which are electron carriers. These molecules are crucial for oxidative phosphorylation, the final stage of cellular respiration where the majority of ATP is produced.

Fructose-1,6-bisphosphatase is an enzyme that catalyzes the reverse reaction of the PFK-1 step in glycolysis, bypassing it in gluconeogenesis. It converts fructose-1,6-bisphosphate to fructose-6-phosphate, helping to generate glucose.

Glucagon is a hormone that is released by the pancreas in response to low blood glucose levels. It stimulates gluconeogenesis in the liver, leading to increased glucose production and restoring blood sugar levels.

Carnitine is essential for the transport of long-chain fatty acids into mitochondria. It acts as a shuttle, carrying these fatty acids across the mitochondrial membrane so they can undergo beta-oxidation.

Hormone-sensitive lipase is an enzyme that catalyzes the breakdown of triglycerides stored in adipose tissue (fat). It is activated by hormones like adrenaline and glucagon, releasing fatty acids into the bloodstream.

The primary product of beta-oxidation is acetyl-CoA, which is a two-carbon molecule that enters the citric acid cycle for further energy generation. Each round of beta-oxidation also yields NADH and FADH2.

The liver is the primary site of ketogenesis. When the body is in a state of prolonged fasting or starvation, the liver produces ketone bodies from fatty acids, which can be used as an alternative energy source by the brain.

Excessive beta-oxidation of fatty acids can lead to ketone body accumulation. This can result in metabolic acidosis, a condition where the body is unable to eliminate enough acid, and can have serious consequences.

Cholesterol is synthesized from acetyl-CoA, a two-carbon molecule that is the primary product of carbohydrate and fat metabolism, through a series of complex reactions.

In the synthesis of fatty acids, acetyl-CoA is first converted to malonyl-CoA. This step is catalyzed by acetyl-CoA carboxylase and is the committed step in fatty acid synthesis.

Carnitine acyltransferase I (CAT I) is the enzyme that is inhibited by malonyl-CoA during fatty acid metabolism. This inhibition prevents fatty acids from entering mitochondria for beta-oxidation when the body is actively synthesizing fatty acids.

Glutamate is a key nitrogen donor in amino acid transamination. It can readily accept and donate amino groups due to the presence of its amino group.

Glutamate dehydrogenase is an enzyme that catalyzes the removal of an amino group from glutamate, producing alpha-ketoglutarate and ammonia. This is a key step in amino acid catabolism.

The urea cycle mainly takes place in the cytoplasm and mitochondria of liver cells. It is a series of reactions that convert ammonia, a toxic byproduct of amino acid metabolism, into less toxic urea for excretion.

The toxic ammonia generated during amino acid metabolism is converted into urea in the urea cycle. Urea is then excreted through urine, eliminating excess nitrogen from the body.

During starvation, the body breaks down proteins to obtain amino acids as an energy source. These amino acids can be used to generate glucose through gluconeogenesis, providing energy for the brain and other tissues.

Glutamine plays a role in nitrogen transport between tissues. It can carry ammonia, a toxic nitrogenous waste product, to the liver where it is converted into urea for excretion.

The de novo synthesis of purines begins with ribose-5-phosphate, a five-carbon sugar that is derived from the pentose phosphate pathway. This is the first committed step in the process.

Thymidylate synthase catalyzes the conversion of dUMP to dTMP, a key step in the synthesis of thymine, one of the four DNA bases. This enzyme is crucial for DNA replication.

The salvage pathway in nucleotide metabolism recycles purine and pyrimidine bases, allowing them to be reused. This process conserves energy and resources compared to de novo synthesis.

PRPP synthase is responsible for the synthesis of phosphoribosyl pyrophosphate (PRPP). PRPP is a key intermediate in nucleotide metabolism, serving as a substrate for both purine and pyrimidine biosynthesis.

Carbamoyl phosphate synthetase I (CPS I) catalyzes the first committed step in the urea cycle. It combines ammonia with bicarbonate and phosphate to form carbamoyl phosphate, which is then used to generate citrulline.

Hydrogen bonds are the primary bonds holding base pairs together in the DNA double helix. These bonds are weak individually but collectively contribute to the stability of the double helix.

Helicase is an enzyme that unwinds the DNA double helix, separating the two strands. This process is necessary for DNA replication and transcription.

In DNA, adenine (A) always pairs with thymine (T). This specific pairing is due to the formation of two hydrogen bonds between these bases.