Cell Metabolism Review Flashcards

Flashcards covering key concepts from Cell Metabolism, including types of reactions, metabolic processes, nutrient handling (carbohydrates, lipids, proteins), and the absorptive/postabsorptive states.

What is the general mechanism by which phosphorylation and dephosphorylation impact enzymes?

They are a common mechanism for activating and deactivating enzymes.

In terms of electron transfer, what is oxidation?

Oxidation is the process of removing electrons from an atom or molecule.

In terms of electron transfer, what is reduction?

Reduction is the process of accepting electrons by another atom or molecule.

Which molecule is typically responsible for removing and accepting electrons in oxidation-reduction reactions, such as cellular respiration?

Oxygen (O2).

What is hydrolysis?

Hydrolysis is a chemical reaction where water reacts with molecules, breaking bonds.

What is the definition of metabolism?

Metabolism encompasses all of the biochemical reactions that occur in a cell, including both the synthesis and breakdown of organic molecules.

What metabolic process involves producing larger molecules from smaller reactants, often requiring energy?

Anabolism.

What metabolic process involves breaking down larger molecules into smaller products, often releasing energy?

Catabolism.

What is a metabolic pathway?

A metabolic pathway is a series of steps in which the products of one reaction serve as the reactants in the next reaction.

What are the three main macronutrients?

Carbohydrates, proteins, and lipids.

How are carbohydrates and proteins absorbed into the body immediately after digestion in the small intestine?

They are absorbed directly into the bloodstream at blood capillaries.

How are lipids absorbed into the body immediately after digestion in the small intestine?

Lipids are absorbed into the lymphatic system via lymphatic capillaries called lacteals first, and then transported to the bloodstream later.

Besides producing energy or being used for anabolic processes, what are other possible fates of absorbed macronutrients?

They can be converted to one another (e.g., sugars to fats), or used for less common functions like making membrane phospholipids or hormone precursors.

Which type of vitamin, water-soluble or lipid-soluble, can readily become toxic in high doses?

Lipid-soluble vitamins (ADEK).

What is the primary site of absorption for most nutrients in the body?

The small intestine (mostly duodenum).

Which organ has high metabolic needs, depends mostly on glucose, and does not store any nutrients?

The brain.

Which organ releases hormones like insulin and glucagon to control when nutrients are stored and released?

The pancreas.

What is the primary site for the storage of excess nutrients, specifically glycogen?

The liver (skeletal muscle also stores glycogen).

Which tissue stores more excess nutrients as fat (triglycerides)?

Adipose tissue.

What is cellular respiration?

Cellular respiration is a metabolic pathway that breaks down organic molecules (catabolism) to make ATP, often referred to as glucose oxidation.

What is the first stage of cellular respiration, which breaks down carbohydrates in the cytoplasm and does not require oxygen?

Glycolysis.

What is the net gain of ATP from glycolysis?

A net gain of 2 ATP.

If oxygen is not present, what is formed as a byproduct of glycolysis, and how much ATP is ultimately produced?

Lactic acid is formed, and very little ATP is ultimately formed.

Where do the Krebs cycle and oxidative phosphorylation occur within the cell?

In the mitochondria.

Does the Krebs cycle require oxygen?

Yes, it requires oxygen (aerobic).

What is a byproduct of the Krebs cycle?

Carbon dioxide (CO2).

What is produced as a byproduct during oxidative phosphorylation and the electron transport system?

Water (H2O).

What is the total ATP yield from a single molecule of glucose if oxygen is present during aerobic cellular respiration?

36-38 ATPs.

What enzyme breaks down complex dietary carbohydrates like starch into smaller sugars before absorption?

Amylase (salivary/pancreatic).

What is glycogenesis?

Glycogenesis is the synthesis of glycogen.

Is glycogenesis an anabolic or catabolic process?

Glycogenesis is an anabolic process.

Where is glycogen primarily stored in the body?

Skeletal muscle (75%) and liver (25%).

Is glucose catabolism (breakdown to ATP, water, and CO2) an anabolic or catabolic process?

These processes are catabolic.

What is glycogenolysis?

Glycogenolysis is the breakdown of glycogen back to glucose.

Is glycogenolysis an anabolic or catabolic process?

Glycogenolysis is a catabolic process.

Can skeletal muscle release its stored glucose back into the bloodstream for use by other body tissues?

No, skeletal muscle uses its own stored glucose but does not share it with the body.

What is gluconeogenesis?

Gluconeogenesis is the process where glucose is formed in the liver from amino acids and fatty acids, often during starvation or low-carbohydrate diets.

What two substances are responsible for breaking down triglycerides into fatty acids and glycerol prior to lipid absorption?

Bile acids (salts) for emulsification and pancreatic lipase.

What are chylomicrons?

Chylomicrons are bubbles of lipids with a protein coat, which allow dietary lipids to be transported in the blood after absorption at the intestine.

Compared to carbohydrates, how much more energy per gram do lipids produce when catabolized for ATP?

About 3X more energy per gram.

Is lipogenesis (the process of storing fat) an anabolic or catabolic process?

Lipogenesis is an anabolic process.

What is a ketogenic diet, and how does it affect the body's metabolism?

A ketogenic diet typically consists of 75% fat, 20% protein, and 5% carbohydrates, causing the body to shift most catabolic processes to burning mostly fats and producing ketone bodies for energy, especially for the CNS.

What clinical condition can arise if ketone bodies are produced excessively, leading to an alteration of the body's pH?

Ketoacidosis.

Where does dietary protein digestion begin?

In the stomach, with pepsin and pancreatic enzymes breaking proteins into peptides.

What is anabolism of proteins called?

Proteogenesis.

How are excess amino acids stored in the body?

Excess amino acids are converted to glucose or triglycerides, not stored as proteins.

What is the process called when the amine group is removed from amino acids prior to catabolism?

Deamination.

What toxic substance is produced during deamination, and how is it processed in the body?

Ammonia (toxic) is produced and then converted to urea (less toxic) in the liver, which is subsequently excreted in urine by the kidneys.

What is the normal homeostatic range for blood glucose that must be maintained for the brain?

70 - 100 mg/dl.

Which hormone is released from the pancreas during the absorptive (fed) state when glucose levels are high, shifting the body towards anabolic reactions?

Insulin.

In the absorptive state, if there are excess carbohydrates, proteins, or lipids, what process occurs for storage in adipose tissue?

Lipogenesis, where they are stored as triglycerides.

Which hormone is released from the pancreas during the postabsorptive (fasted) state when blood glucose drops, shifting the body towards catabolic reactions?

Glucagon.

During the postabsorptive state, how does the liver maintain blood glucose levels for the brain?

Through glycogenolysis, breaking down stored glycogen and releasing glucose into the blood.

During periods of starvation (long periods without glucose), what alternative energy source can the liver produce from excessive fat breakdown for the CNS?

Ketone bodies (ketogenesis).

What major body component is ultimately broken down for gluconeogenesis after weeks of starvation?

Skeletal muscle protein.