Digestion & Metabolism Flashcards
What is digestion?
The process of breaking down food into absorbable nutrients.
What is metabolism?
Utilizing nutrients from digestion to generate cellular energy.
What is the sequence of energy processes after digestion?
Digestion -> Absorption -> Metabolism
What is a calorie?
The amount of energy needed to raise the temperature of 1 gram of water by 1°C.
What is the “Eat or Exercise Activity Thermogenesis”?
Energy expended through physical activity, which can be increased by exercise.
What is the “Thermic Effect of Food”?
The energy required to digest food. Protein digestion requires more energy.
What is Basal Metabolic Rate (BMR)?
The amount of energy expended while at rest. It can increase in heat.
What are some factors affecting BMR?
BMR varies by individual, is correlated with body size, is higher in men, and decreases with age.
What is the digestive system responsible for?
Breaking down food into absorbable nutrients: amino acids, lipids, mono/disaccharides, vitamins.
What are the key steps in digestion?
- Mouth
- Stomach
- Small intestine
What happens in the mouth during digestion?
Chewing (mechanical digestion) and saliva secretion (chemical digestion).
What are the key components of saliva?
Amylase, lingual lipase (for lipids), lysozyme, IgA, epithelial cells, biomarkers.
What is the role of the epiglottis?
A cartilage flap that prevents food from entering the trachea during swallowing.
What is the function of the esophagus?
A muscle-lined tube that helps food travel to the stomach in just a few seconds.
What happens in the stomach during digestion?
Both chemical and mechanical digestion. The stomach holds food for 1-4 hours.
What enzymes are involved in stomach digestion?
Hydrochloric acid and pepsin (breaks down proteins).
How long can the stomach hold food and what is its pH?
The stomach holds food for 1-4 hours, and its pH is around 1-3, aiding in digestion and killing bacteria.
What are the three salivary glands?
Parotid, submandibular, and sublingual glands.
What is the role of the salivary glands?
They secrete saliva, which aids swallowing and begins chemical digestion.
What is the function of the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles?
They are involved in the mechanical breakdown of food by chewing.
What is the role of the tongue in digestion?
The tongue helps in swallowing and the mechanical breakdown of food.
Why is the pH of saliva important?
The near-neutral pH (~6.7) helps prevent tooth decay and acts as a buffer.
What does the stomach’s acidity do?
It helps break down proteins and kills most bacteria and viruses.
What are the layers of muscles in the stomach?
The stomach has three muscle layers that are cross-layered, aiding in food breakdown.
What is the function of hydrochloric acid in the stomach?
It activates enzymes like pepsin and helps digest proteins.
How much food can the stomach hold?
The stomach can hold about 1.5 liters of food.
What is the role of the pancreas in digestion?
The pancreas produces hydrochloric acid and digestive enzymes (like pepsin) that are secreted into the stomach.
What are the main functions of saliva in digestion?
Saliva helps with swallowing, begins chemical digestion (especially with enzymes like amylase and lingual lipase), and kills pathogens.
What is the difference between mechanical and chemical digestion?
Mechanical digestion involves physically breaking down food (e.g., chewing), while chemical digestion involves enzymes breaking down food on a molecular level.
What do gastric glands produce in the stomach?
They produce a thick mucosal layer that protects the stomach lining.
What does the mucosa of the stomach contain, and what is its function?
The mucosa contains sodium bicarbonate, which acts as a buffer (similar to what antacids are made of).
What is the primary function of the stomach in digestion?
The stomach is mainly involved in breaking down food, with minimal absorption.
What are villi, and where are they found?
Villi are tiny hair-like structures in the small intestine that help increase surface area for absorption.
How long is the small intestine?
The small intestine is the longest part of the digestive tract, about 22 feet long.
Why is the surface area of the small intestine so large?
The villi in the small intestine greatly increase the surface area, making it roughly the size of a tennis court.
How many sections does the small intestine have, and do they have different purposes?
The small intestine has 3 sections, each with slightly different purposes.
What is the first section of the small intestine called?
The first section is called the duodenum.
What unique characteristic does the duodenum have?
The duodenum receives bile from the liver, gallbladder, and pancreas and helps neutralize stomach acid.
Where does most enzymatic digestion occur?
Most enzymatic digestion occurs in the duodenum
What is the duodenum important for in terms of nutrient intake?
The duodenum is important for sensing nutrient intake
What happens to peptides and fats in the duodenum?
Peptides are broken down, and fats are converted into smaller droplets by bile salts.
What are the 2nd and 3rd sections of the small intestine?
The jejunum and ileum.
What are the key differences between the jejunum and ileum?
They have subtle anatomical differences but overlap in their functions.
What happens in the jejunum and ileum in terms of digestion?
More food breakdown occurs, and there is a lot of absorption.
How are sugars and amino acids absorbed in the jejunum and ileum?
Sugars and amino acids are transported into cells by transporters.
How are lipids absorbed in the jejunum and ileum?
Lipids can move across the membrane but enter the lymphatic system instead of the hepatic system.
What does the gastric mucosa contain to protect the stomach lining?
Sodium bicarbonate, which acts as a buffer.
Why is sodium bicarbonate important in the stomach?
It buffers the stomach’s acid, helping protect the stomach lining from the acidic environment.
What happens to food in the stomach?
The stomach mainly breaks down food, with minimal absorption.
Where can lipids enter the bloodstream?`
near the jugular via thoracic duct
The large intestine is about how many feet long?
5ft
what is the primary function of the large intestine?
to absorb water
What is the function of chylomicrons?
They transport lipids around the bloodstream and deliver fats to cells for maintenance.
What happens to chylomicrons after transporting fats?
They are converted into other types of lipoproteins.
How does the liver use triglycerides from chylomicrons?
The liver uses triglycerides for anabolism.
What are lipoproteins?
Fat globules that transport lipids through the body.
What is catabolism?
A set of metabolic pathways that break down molecules to release energy or prepare them for anabolic reactions.
What is anabolism?
A set of metabolic pathways that build molecules from smaller units, requiring energy (endergonic process).
Why is the liver important in metabolism?
It regulates metabolism and anabolism, performing over 500 chemical reactions and producing/storing glycogen.
What are some ways energy is used around the body?
Cellular regeneration
Maintaining cellular integrity
Ion gradient
mRNA synthesis
Anabolism
Heat from ETC
Muscle movement
What is the primary role of chylomicrons in lipid transport?
They carry dietary lipids, especially triglycerides, from the intestines to cells and the liver.
How do cells use the fats transported by chylomicrons?
Cells use them for energy, membrane maintenance, and storage.
Q: What happens to chylomicron remnants after fat delivery?
They are taken up by the liver and repackaged into other types of lipoproteins.
What are the main types of lipoproteins?
Chylomicrons, VLDL (very low-density lipoproteins), LDL (low-density lipoproteins), and HDL (high-density lipoproteins).
What is the difference between LDL and HDL?
LDL delivers cholesterol to cells and can contribute to plaque buildup, while HDL removes excess cholesterol and carries it to the liver for disposal.
Q: What is the primary function of triglycerides in metabolism?
They serve as a major energy storage form and can be broken down for ATP production.
How does the liver contribute to lipid metabolism?
It processes lipids, converts excess carbohydrates into fats, and synthesizes lipoproteins.
What is the role of glycogen in metabolism?
It is a stored form of glucose in the liver and muscles, used for quick energy release when needed.
What is ATP, and why is it important?
ATP (adenosine triphosphate) is the main energy currency of the cell, fueling biochemical reactions.
How does the electron transport chain (ETC) contribute to metabolism?
The ETC generates ATP and produces heat as a byproduct, helping regulate body temperature.
Why is anabolism considered an endergonic process?
It requires energy input to build complex molecules from smaller ones
What is the primary difference between catabolic and anabolic pathways?
Catabolic pathways break down molecules and release energy, while anabolic pathways build molecules and require energy.
How does metabolism support muscle movement?
ATP fuels muscle contraction and relaxation, allowing movement and physical activity.
What role does metabolism play in maintaining cellular integrity?
It provides energy for repairing cell membranes, producing proteins, and sustaining organ function.
