Biology: Digestion and Nutrition

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Questions and Answers

What is the role of bile in the small intestine?

To aid in digestion and absorption of fats (correct)

To activate proteases

To destroy functional red blood cells

To neutralize acidic chyme

Where does most digestion occur in the small intestine?

Duodenum (correct)

Jejunum

Ileum

Stomach

What is the function of the epithelial lining of the duodenum?

To produce acidic digestive enzymes

To absorb fatty acids and monoglycerides

To produce alkaline digestive enzymes

To produce several digestive enzymes (correct)

What is the role of the pancreas in the small intestine?

To produce proteases trypsin and chymotrypsin Signup and view all the answers

What is the function of villi epithelial cells in the small intestine?

To absorb fatty acids and monoglycerides Signup and view all the answers

What is the role of chylomicrons in the small intestine?

To transport fatty acids and monoglycerides Signup and view all the answers

What is the main function of the jejunum and ileum in the small intestine?

Absorption of nutrients and water Signup and view all the answers

What is the role of the liver in the small intestine?

To produce bile Signup and view all the answers

Where does the breakdown of glucose polymers initiated by salivary amylase take place?

Mouth Signup and view all the answers

What is the function of mucus in saliva?

Lubricates food Signup and view all the answers

What is the role of the epiglottis during swallowing?

Blocks entry to the trachea Signup and view all the answers

What is the pH of gastric juice in the stomach?

Low, around 2 Signup and view all the answers

What is the function of pepsin in gastric juice?

Breaks down proteins Signup and view all the answers

What is the role of parietal cells in the stomach?

Secrete hydrogen and chloride ions Signup and view all the answers

What is the function of chief cells in the stomach?

Secrete pepsinogen Signup and view all the answers

What prevents chyme from entering the esophagus during digestion?

Sphincters Signup and view all the answers

What is the primary function of lysosomes in intracellular digestion?

To fuse with food vacuoles to release hydrolytic enzymes Signup and view all the answers

Which of the following is a characteristic of extracellular digestion?

The breakdown of food particles occurs outside of cells Signup and view all the answers

What is the primary function of the gallbladder in the mammalian digestive system?

To store and concentrate bile Signup and view all the answers

What is the difference between a gastrovascular cavity and a complete digestive tract?

The presence of an alimentary canal with two openings Signup and view all the answers

Which stage of feeding is characterized by the uptake of nutrients by cells?

Absorption Signup and view all the answers

What is the primary function of the salivary glands in the mammalian digestive system?

To produce digestive enzymes that break down carbohydrates Signup and view all the answers

Which of the following is a characteristic of intracellular digestion?

Food particles are engulfed by phagocytosis and broken down by hydrolytic enzymes Signup and view all the answers

What is the primary function of the pancreas in the mammalian digestive system?

To produce digestive enzymes that break down proteins and carbohydrates Signup and view all the answers

What is the primary mechanism by which sponges capture food particles?

Phagocytosis Signup and view all the answers

In cnidarians, where does digestion take place?

Gastrovascular cavity Signup and view all the answers

What is the common characteristic of animals with bilateral symmetry in terms of digestion?

Complete digestive system with an entrance and an exit Signup and view all the answers

What is unique about the digestive system of mammals?

Complex digestive system with a mouth, esophagus, stomach, small intestine, and large intestine Signup and view all the answers

What is the stage of feeding characterized by the breakdown of food into smaller molecules?

Digestion Signup and view all the answers

In which stage of feeding do cells absorb nutrients through endocytosis?

Absorption Signup and view all the answers

What is the process by which unused substances are discarded in sponges?

Exocytosis Signup and view all the answers

What is the mechanism by which enzymes break down food in cnidarians?

Exocytosis Signup and view all the answers

What is the primary function of energy in animals?

To support growth and maintenance Signup and view all the answers

Which of the following is NOT a macronutrient?

Vitamins Signup and view all the answers

What is the primary source of energy for herbivores?

Plants Signup and view all the answers

During which process do animals obtain energy?

Digestion Signup and view all the answers

What is the primary consequence of energy imbalance?

Health problems Signup and view all the answers

What is the role of omnivores in the energy cycle?

They obtain energy from plants and animals Signup and view all the answers

What is the primary function of the mucous cells in the stomach?

To produce mucus for protection from acid and enzymes Signup and view all the answers

What is the purpose of the neutralization reaction in the duodenum?

To neutralize the acidic pH from the stomach with basic alkaline secretions Signup and view all the answers

What is the primary function of the glycoproteins in saliva?

To provide lubrication and protection to the mouth and esophagus Signup and view all the answers

What is the primary role of the epithelial lining of the small intestine in relation to fat absorption?

To increase the surface area for absorption through villi Signup and view all the answers

What is the primary function of the triglycerides in fat absorption?

To be broken down into fatty acids and monoglycerides for absorption Signup and view all the answers

What is the primary function of the lacteal in fat absorption?

To transport absorbed fatty acids and monoglycerides to the bloodstream Signup and view all the answers

What is the primary function of the chylomicrons in fat absorption?

To package triglycerides, phospholipids, cholesterol, and proteins for transport Signup and view all the answers

What is the primary function of the bolus in the mouth?

To mix food with saliva for formation of a manageable food mixture Signup and view all the answers

What is the primary advantage of bulk feeding over particle feeding?

Getting a lot of energy in one act Signup and view all the answers

Which of the following animals uses a lure to attract prey?

Angler fish Signup and view all the answers

What is the primary function of tool use in animals?

To obtain food that would be difficult or impossible to obtain otherwise Signup and view all the answers

Which of the following groups of animals is known for their high hunting effectiveness?

African wild dogs Signup and view all the answers

What is the primary benefit of group feeding in animals?

Increased food capture efficiency Signup and view all the answers

Which of the following is an example of deception in feeding strategies?

Angler fish using a lure to attract prey Signup and view all the answers

What is the primary difference between bulk feeding and particle feeding?

The size of the food particles Signup and view all the answers

Which of the following is NOT an advantage of bulk feeding?

Increasing the speed of digestion Signup and view all the answers

What is the primary function of essential amino acids in animals?

To serve as building blocks for proteins Signup and view all the answers

What is the primary difference between complete and incomplete proteins?

The presence of all essential amino acids Signup and view all the answers

What is the primary function of vitamins in animals?

To facilitate chemical reactions Signup and view all the answers

What is the primary consequence of iron overload in animals?

Hemochromatosis Signup and view all the answers

What is the primary stage of food processing where nutrients are absorbed into the bloodstream?

Absorption Signup and view all the answers

What is the primary function of essential fatty acids in animals?

To serve as building blocks for lipids Signup and view all the answers

What is the primary difference between fat-soluble and water-soluble vitamins?

The ability to be stored in the body Signup and view all the answers

What is the primary consequence of a diet lacking essential nutrients?

Malnutrition Signup and view all the answers

What is the primary function of the large intestine in the digestive system?

Water absorption and waste elimination Signup and view all the answers

Which type of feeder is characterized by the consumption of large amounts of food at one time?

Bulk feeder Signup and view all the answers

What is the primary function of gastrin in the digestive system?

To prepare the stomach for digestion Signup and view all the answers

What is the primary function of the rumen in the digestive system of ruminants?

To break down undigested plant material Signup and view all the answers

What is the primary function of the cephalic phase of digestion?

To prepare the stomach for digestion Signup and view all the answers

What is the primary function of the hormone secretin in the digestive system?

To stimulate the release of pancreatic juices Signup and view all the answers

What is the primary function of the hormone CCK in the digestive system?

To stimulate the release of bile and pancreatic juices Signup and view all the answers

What is the primary function of the gut flora in the large intestine?

To break down undigested plant material Signup and view all the answers

What is the primary function of the hormone leptin in regulating body weight?

To reduce appetite Signup and view all the answers

What is the primary function of insulin in regulating glucose levels in the blood?

To convert glucose to glycogen Signup and view all the answers

Study Notes

Digestion and Nutrition

There are three types of nutrients: those that can be made in the body, those obtained only by eating plants, and those obtained only by eating animals.

Digestion Forms

Digestion involves four stages: ingestion, digestion, absorption, and elimination.
Intracellular digestion occurs when food particles are engulfed by phagocytosis, and then fuse with lysosomes containing hydrolytic enzymes.
Extracellular digestion occurs outside of cells, in compartments that are continuous with the outside of the animal's body, and can be found in animals with simple body plans.
More complex animals have a complete digestive tract or alimentary canal, which can have specialized regions for digestion and absorption.

Mammalian Digestive System

The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices.
Accessory glands include salivary glands, pancreas, liver, and gallbladder.
The small intestine is the longest section of the alimentary canal, and is the major organ of digestion and absorption.

Digestion in the Small Intestine

The small intestine is divided into three parts: duodenum, jejunum, and ileum.
The pancreas produces proteases trypsin and chymotrypsin that are activated in the duodenum.
Bile from the liver and gallbladder aids in digestion and absorption of fats.
The epithelial lining of the duodenum produces several digestive enzymes, and enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine.
Most digestion occurs in the duodenum, while the jejunum and ileum function mainly in absorption of nutrients and water.

Absorption of Fats

Villi epithelial cells absorb fatty acids and monoglycerides, and recombine them into triglycerides.
These fats are coated with phospholipids, cholesterol, and proteins to form water-soluble chylomicrons.
Chylomicrons are transported into a lacteal, a lymphatic vessel in each villus, and delivered to large veins that return blood to the heart.

Digestion in the Mouth

Salivary glands deliver saliva to lubricate food and initiate breakdown of glucose polymers.
Teeth chew food into smaller particles, and saliva contains mucus, a viscous mixture of water, salts, cells, and glycoproteins.
The tongue shapes food into a bolus and provides help with swallowing.

Digestion in the Stomach

Gastric juice has a low pH of about 2, which kills bacteria and denatures proteins.
Gastric juice is made up of hydrochloric acid (HCl) and pepsin, a protease that cleaves proteins into smaller peptides.
Parietal cells secrete hydrogen and chloride ions separately into the lumen of the stomach.
Chief cells secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in the stomach.
Mucus protects the stomach lining from gastric juice.

Types of Digestive Strategies

Digestive strategies involve four stages: ingestion, digestion, absorption, and elimination.

Sponges

Sponges are primitive animals with simple bodies made up of cells, but no tissues, organs, or organ systems.
They are filter feeders, using incurrent canals to bring in small particles of food, including decaying bodies.
Coanocytes capture food particles through phagocytosis, forming a food vacuole.
Enzymes in vesicles break down food into smaller molecules, which are then used by the cell or shared with other cells.
Unused substances are discarded through exocytosis, and metabolic wastes like CO2 diffuse through the plasma membrane.

Cnidarians

Cnidarians, like cnidarians and comb jellies, have extracellular digestion, where food is broken down outside of cells.
Ingestion occurs through a mouth, and digestion takes place in the gastrovascular cavity.
Enzymes are released into the cavity through exocytosis, breaking down food into smaller particles.
Cells lining the cavity absorb nutrients through endocytosis, and unused materials are discarded through exocytosis.

Bilaterally Symmetrical Animals

Animals with bilateral symmetry, like segmented worms, arthropods, and birds, have a complete digestive system with an entrance (mouth) and an exit (anus).
Ingestion occurs through the mouth, and digestion takes place in the digestive system, often with mechanical breakdown (e.g., chewing mandibles, gizzard).
Absorption occurs along the intestine, and excretion occurs through the anus.
Variations include a crop for storing food, a cloaca for reproductive and excretory systems, and structures like the gizzard for mechanical breakdown.

Mammalian Digestive System

Mammals have a complex digestive system, with a mouth, esophagus, stomach, small intestine, and large intestine.
Ingestion occurs through the mouth, and mechanical digestion occurs with teeth.
Chemical digestion occurs in the stomach with enzymes, and accessory glands aid in digestion.
Absorption occurs in the small intestine, and the large intestine recycles water before excretion through the anus.

Energy and Nutrition

Energy is vital for animals to survive, thrive, and maintain bodily functions
Animals obtain energy by consuming other organisms or plants, which provide energy for growth and maintenance

Macronutrients

Carbohydrates, lipids, and proteins are the three primary macronutrients essential for energy and growth
These macronutrients provide energy and support various bodily functions, including growth and maintenance

Energy Sources

Plants are the primary energy source for many animals, serving as a food source for herbivores
Herbivores, such as cows and deer, obtain energy by consuming plants
Carnivores, such as lions and tigers, obtain energy by consuming other animals
Omnivores, such as humans and bears, obtain energy by consuming both plants and animals

Digestion and Absorption

Digestion breaks down nutrients into smaller molecules, releasing energy for the body
Absorption involves the uptake of these molecules into the bloodstream, providing energy for the body
Energy is obtained from nutrient breakdown during digestion and absorption, supporting bodily functions

Importance of Energy

Energy is crucial for survival, growth, and maintenance of bodily functions
Energy is necessary for physical activity, supporting muscle movement and exercise
Energy imbalance can lead to health problems, such as obesity, diabetes, and malnutrition

Mammalian Digestive System

Mammals have fewer compartments in their digestive system compared to other vertebrates
The digestive system consists of the mouth, esophagus, stomach, and intestines (small and large) for digestion, absorption, and excretion

Mouth

The mouth is the first stage of digestion
Salivary glands produce saliva containing amylase, mucous, water, salts, and glycoproteins
Amylase breaks down polysaccharides into smaller polysaccharides and disaccharides
Mucous helps food move through the esophagus
Formation of bolus occurs in the mouth

Esophagus

The esophagus is responsible for the passage of food to the stomach
The epiglottis, a valve, prevents food from entering the respiratory tract

Stomach

The stomach has gastric pits, which are finger-like projections
Parietal cells in the stomach secrete hydrogen ions and chloride ions
Chief cells are the majority of cells in the stomach
Mucous cells produce mucus for protection
The stomach has a pH of 2 due to hydrochloric acid, which breaks down proteins and activates pepsinogen
Pepsin, a protease, breaks down protein molecules into smaller polypeptides

Small Intestine

The small intestine is the main place for chemical digestion
The small intestine is divided into three sections: duodenum, jejunum, and ileum
The duodenum is where food from the stomach mixes with digestive materials from the pancreas, liver, gallbladder, and small intestine lining cells
A neutralization reaction occurs in the duodenum (acidic pH 2 + basic alkaline secretions)
The pancreas produces a variety of enzymes, including protease, amylase, and lipase
Enzymes are activated in the duodenum
Bile, produced by the liver and stored in the gallbladder, is responsible for the digestion and absorption of fats
Epithelial cells lining the small intestine produce digestive enzymes, such as amylase and carboxy peptidase

Fat Absorption

Villi on epithelial cells increase the surface area for absorption
Triglycerides are broken down into fatty acids and monoglycerides
Absorption occurs into cells, where triglycerides are reformed and packaged into chylomicrons
Chylomicrons contain triglycerides, phospholipids, cholesterol, and proteins
Chylomicrons are released into lacteal, a lymphatic vessel, for transport to the blood and eventually to the heart and body parts

Feeding Strategies

Particle feeding: collecting small particles, often dead organisms, for essential nutrients.
Bulk feeding: consuming large items, such as prey, for a lot of energy.

Modifying Food Supply

Leaf-cutter ants: collecting leaves, carrying them underground, and allowing fungi to break down cellulose into protein-rich food.
Aphid-hurting ants: collecting aphids, protecting them from enemies, and benefiting from sweet, sugary secretions (honeydew).

Traps and Deception

Spiders: setting up webs, traps, and using deception to catch prey.
Ant lions: creating funnel traps in sand and sucking juices from trapped insects using modified mandibles.
Angler fish: using a lure on their dorsal fin to attract prey and swallowing them whole.
Deception: some animals use deception to attract prey, such as moths attracted to a spider's silk and pheromone imitation.

Tool Use

Chimps: using sticks to extract termites from mounds.
Egyptian vultures: using rocks to crack open ostrich eggs.
Tool use: using an object to obtain food that would be difficult or impossible to obtain otherwise.

Group Feeding

Advantages of group feeding: increased food capture efficiency, reduced search area, and lower risk of predation.
Examples of group feeding: lions, hyenas, wild dogs, dolphins, grey whales, and Harris hawks.
Strategies of group feeding: cooperation, communication, and coordination to hunt and catch prey.

Comparison of Hunting Effectiveness

Lions: 50% hunting effectiveness, often scavenging instead of hunting.
Hyenas: 70% hunting effectiveness, using coursing to chase and exhaust prey.
African wild dogs: 90% hunting effectiveness, using stamina to chase and exhaust prey.
Harris hawks: group hunting in the desert, using perched and flying birds to catch prey.

Animal Nutrition

Animals require energy, building blocks, and essential nutrients like vitamins and minerals to survive.
There are three types of animals: herbivores, carnivores, and omnivores, each with unique nutritional needs.

Protein Nutrition

There are 20 amino acids, with 9 essential amino acids that cannot be synthesized by animals.
Complete proteins (meat, eggs, cheese) provide all essential amino acids, while plant proteins are incomplete.

Lipid Nutrition

Animals can synthesize fatty acids, but must obtain essential fatty acids from their diet.
Essential fatty acids are unsaturated and cannot be synthesized by animals.

Vitamin and Mineral Nutrition

There are 13 vitamins, which are organic molecules required for chemical reactions.
Vitamins can be fat-soluble (stored in the body) or water-soluble (excess excreted).
Minerals are inorganic molecules required for various bodily functions.

Nutritional Deficiencies

Malnutrition occurs when the diet lacks essential nutrients.
Undernutrition occurs when the diet lacks sufficient energy or nutrients.
Examples of nutritional deficiencies: hemochromatosis (iron overload), neural tube defects (folic acid deficiency).

Digestive System

There are four stages of food processing: ingestion, digestion, absorption, and elimination.
Types of feeders: suspension feeders, substrate feeders, fluid feeders, and bulk feeders.

Mouth and Esophagus

Mouth: mechanical digestion (teeth, tongue) and salivary glands (saliva, amylase).
Esophagus: peristalsis (muscular contractions) and epiglottis (blocks trachea during swallowing).

Stomach

Gastric juices: hydrochloric acid, pepsin, and mucus.
Parietal cells produce hydrogen and chloride ions, and chief cells produce pepsinogen.

Small Intestine

Longest section of the elementary canal, where most digestion and absorption occur.
Pancreatic juices (enzymes, bicarbonate) and bile salts aid in digestion.
Villi increase surface area for absorption.

Large Intestine

Absorbs water and electrolytes, and houses gut flora for fermentation of undigested plant material.
Cecum is a specialized region for fermentation.
Colon, rectum, and anus are involved in waste elimination.

Ruminants and Digestion

Ruminants, such as cows, have a mutualistic relationship with microorganisms to break down undigested plant material.
The cow's digestive system involves the rumen, reticulum, omasum, and abomasum.

Feedback Circuits and Digestion

Feedback circuits regulate digestion and energy storage based on available food and nutrients.
The nervous system and endocrine system work together to control digestion.
Hormones regulate digestion, such as gastrin, secretin, and CCK.

Hormones and Digestion

Gastrin is released in the stomach to prepare gastric juices for digestion.
Secretin and CCK are released in the small intestine to break down food and neutralize acidic chyme.
CCK also helps to release bile to break down fats.

Energy Storage and Cellular Respiration

Excess energy is stored in the liver and muscle cells as glycogen.
Excess energy beyond that is stored in adipose tissue as fat.
Insulin and glucagon are hormones that help to regulate glycogen breakdown and glucose formation.

Glucose Regulation and Homeostasis

Insulin helps to convert glucose to glycogen when blood sugar levels are high.
Glucagon breaks down glycogen to glucose when blood sugar levels are low.
This feedback loop helps to maintain homeostasis of glucose levels in the blood.

Regulation of Body Weight

Hormones such as leptin, ghrelin, insulin, and PYY help to regulate appetite and body weight.
Leptin reduces appetite when present, but its decrease can increase appetite.
Ghrelin triggers hunger feelings, while insulin and PYY help to suppress appetite.

Evolution and Body Weight

The ability to maintain body weight is important for survival in times of famine.
Examples of species that have adapted to maintain body weight, such as the pygmy birds, demonstrate the importance of this trait in evolution.

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Description

This quiz covers the processes of digestion, nutrition, and absorption in living organisms. It includes stages of feeding, intracellular digestion, and sources of nutrients.