Chapter 9 Flashcards
Define nutrient
a chemical that must be obtained by an organism from its environment in order to survive
Food for Growth and Maintenance
- carbohydrates
- proteins
- lipids
- water
- vitamins
- minerals
Broken down into simpler molecules that are used to build and repair bone, muscle, cells, and tissues.
Food for Energy
- all organisms need chemical energy
- humans obtain chemical energy carried in animal and plant-based foods
- cells in the body use chemical energy to fuel biological processes
Define metabolism
a set of chemical reactions that occur in living organisms that are necessary to maintain life
Define catabolism
the metabolic reactions that break down larger molecules into smaller subunits
Define anabolism
the metabolic reactions that use energy to produce larger molecules from smaller subunits
Metabolic rate
the rate at which the body converts stored energy into working energy
Factors that affect metabolic rate
- body size
- physical activity
- sex
- age
- hereditary factors
Measuring energy
1 calorie = 4180 J
Define macronutrients
a substance required in relatively large amounts by living organisms
- carbs, lipids, proteins, water
Define micronutrients
a chemical element or substance required in very small amounts by living organisms
- vitamins, minerals
Macronutrients: carbohydrates
- when we digest carbohydrates, they are broken down into simple sugar (monosaccharides)
- made up of C, H, O
- main energy source
- foods high in carbs are vegetables, fruits, potatoes, grains
3 types - Monosaccharides (ie. glucose)
- Disaccharides (ie. sucrose, table sugar)
- Polysaccharides (ie. cellulose, starch)
Macronutrients: protein
- when we digest proteins, they are broken down into amino acids
- made up of C, H, O, N
Functions - building blocks of cells
- involved in movement and biochemical reactions
- hormones
- enzymes
20 different types of amino acids - 12 non essential (can be made by the body)
- 8 essential (ie. through food)
Foods high in protein are meat, eggs, cheese, nuts
Macronutrients: lipids
- when we digest triglycerides (fats and oils), they are broken down into fatty
- made up of C, H, O
Functions - secondary source of energy after carbohydrates
- helps with absorption of vitamins
- insulation for the body
- some types of hormones
Saturated vs. Unsaturated fats
Saturated fats
- usually solid at room temp
- considered to be less healthy
- ie. butter
Unsaturated fats
- usually liquid at room temp
- considered to be more healthy
- ie. vegetable oil
Macronutrients: water
- the body is made up of 50-60% water
Functions - required to make cytoplasm of cell
- perform chemical reactions
- blood volume
- regulates blood temperature
- keeps skin moist
Replace water lost through: - urine
- sweat
- respiration
Micronutrients: vitamins
Fat-soluble (vitamins A, D, E, K)
- these vitamins can be stored in the body’s fatty tissues for future use
- not easy to eliminate excess from the body
Water soluble (vitamin B, C)
- cannot be stored in the body
- excess quantities can be excreted in urine
Most vitamins are from food, but vitamins A, D, and K, can be produced in our bodies
Vitamin A, D, K
Vitamin A
- the body can convert a chemical called beta-carotene into vitamin A
Vitamin D
- formed in the skin when skin is exposed to sunlight
- can produce enough vitamin D from 10-15 minutes of sunshine
Vitamin K
- is synthesized by a special bacteria found in the large intestine
Micronutrients: minerals
- minerals are naturally occurring elements that the body uses to carry out metabolic processes and to build or repair tissues
- An element required by the body in small amounts
- Ca, P, Na, Fe are prominent in our bodies (ie. Ca and P for bone formation, Fe for hemoglobin)
- F, Zn, Cu are present in our bodies in trace amounts
Specialized digestive systems: simple animals
gastrovascular cavity - a simple, sac-like digestive cavity that has only one opening where food goes in and wastes are expelled
- chemicals released into the cavity to break down food
- nutrients are absorbed by cells that line the cavity
- digestion continues in the cells
- nutrients diffuse from these cells to other cells of the body
ie. flatworms and jellyfish
Specialized digestive systems: complex animals
- Digestive tract with two openings, one for food and one for waste
- organized into specialized regions that enable the breakdown and absorption of food
Human Digestive System (4 main steps)
Gastrointestinal (GI) tract - the passageway or tube that extends from the mouth to the anus where the process of digestion takes place
1. Ingestion - the taking into the body of sources of nutrients, must be broken down in order for cells to use
2. Digestion - the breakdown of complex food molecules into smaller molecules
Chemical digestion - occurs in the mouth, stomach, and small intestine; chemicals mix with food to break them down into nutrients that could be absorbed
Physical digestion - occurs in the mouth and stomach; solid food is shredded, torn, ground, and mixed to break down food into smaller pieces, increasing the surface area for chemical digestion
3. Absorption - nutrients move from the intestine to the bloodstream
4. Egestion - removal of the waste food materials through the rectum and anus
Physical digestion in the mouth
- food is broken down into smaller pieces by the teeth
- type of teeth an animal has relates to its diet
1. Incisors - used for cutting
2. Canines - used for tearing
3. Premolars - used for grinding
4. Molars - used for crushing
Chemical digestion in the mouth
The presence of food in the mouth triggers the salivary glands to secrete saliva (made up of 90% water, electrolytes, enzymes, mucus)
- Enzymes (chemicals that increase the rate of reactions in living things, such as breaking down food)
ie. amylase is an enzyme that breaks down starch into disaccharides
Swallowing Reflex
- Mucus is a protective secretion that acts as a lubricant and helps with swallowing by moistening food into a ball - bolus)
- The tongue lifts the bolus to the roof of the mouth and pushes it to back of the mouth
- Epiglottis is the flap of tissue at the base of the tongue that keeps food from going into the trachea (windpipe) during swallowing
Esophagus
- an organ consisting of a muscular tube that passes food from the pharynx to the stomach
- bolus of food stretches the walls of the esophagus, activating smooth muscles to undergo wavelike contractions called peristalsis
Stomach (4 layers)
Mucosa - secretes gastric juice
Sub-mucosa - connective tissue that contains networks of nerves and blood vessels
Muscularis - consists of smooth muscle to churn and mixes the contents of the stomach
Serosa - holds the stomach in place and secretes a lubricating fluid that eliminates friction between organs
Sphincters (3 types)
-The muscle that controls the movement of food in the GI tract
1. Upper esophageal sphincter is located at the top of the esophagus
2. Gastroesophageal sphincter is located where the esophagus joins the stomach
3. Pyloric sphincter is located where the stomach joins the small intestine (duodenum)
Physical digestion in the stomach
- J-shaped, muscular organ
- Muscles in the wall of the stomach churn the food to continue physical digestion
Chemical Digestion in the Stomach
- Proteins are partially digested in the stomach and continue digesting the small intestine
- Lipids and carbohydrates are not chemically digested in the stomach
- the nerves in the sub-mucosa initiate the release of a hormone called gastrin into the bloodstream
- gastrin causes the cells of the mucosa to release gastric juice
made up of mucus, acid, and digestive enzymes
Mucus- coats the stomach to protect it from acid and enzymes
Acid- hydrochloric acid (HCl)
- low pH (2.0-3.0) kills microorganisms
- stops amylase from working
- activates pepsinogen–>pepsin
Bolus becomes chyme (semi-liquid mixture of food and gastric juice)
Function of Small intestine
where most digestion and absorption of nutrients takes place
- chemical digestion of carbs, lipids, and proteins
- absorption of nutrients into blood vessels
Chemical digestion in the small intestine
- the pyloric sphincter controls the passage of food from the stomach into the small intestine
- the slow release of chyme into the small intestine prevents overloading and allows time for thorough digestion
- most of the enzymes required for digestion are added to the duodenum
- requires input from accessory organs (pancreas, liver, gallbladder)
Pancreas
- when chyme enters the duodenum, a hormone called cholecystokinin (CCK0 is secreted by special cells in the duodenum and released into the bloodstream
- CCK signals the pancreas to secrete digestive enzymes that are needed for protein (trypsin), carbs (amyalse), and lipid (lipases) digestion
- CCK also signals the stomach to slow down the speed of digestion so that fats can be properly digested
Secretin
- Chyme has a pH of 2-3
- low pH triggers prosecretin from the epithelial cells of the duodenum to be converted into active form of the hormone, secretin
- stimulates the pancreas to release bicarbonate ions (HCO3) to neutralize the acidic chyme in the duodenum and raise the pH 9
- protects the small intestine from stomach acids
Trypsin
- Pepsin is inactivated in basic environment
- To continue protein digestion
Inactive form trypsinogen (from pancreas) through enterokinase to active form trypsin
Amylase
- Amylase (From pancreas) continues the digestion of starch/disaccharides into monosaccharides
Lipases
Lipases (from pancreas) break down lipids –> fatty acid molecules
- fats in chyme are present as large globules and need to be broken down for lipases to chemically digest the lipids
Liver and Gallbladder
Liver - produces and secretes bile
Bile - a substance that emulsifies globules of fats, breaking them into tiny droplets called micelles.
- This gives the lipases a much greater surface area to chemically digest the lipids, and the rate of lipid digestion increases.
Gallbladder – stores bile produced by the liver
Villus
a small, fingerlike projection of the small intestine mucosa
