NUTR 210 Chapter 3

6 levels of organization of the organism

1) atoms linked by chemical bonds to form molecules

2) molecules form the structures that make up cells

3) groups of similar cells form tissues

4) organs are made of several types of tissue

5) group of organs that work together to perform a particular function forms an organ system

6) organ systems work together to ensure proper functioning of the organism

List the organ systems mentioned in lecture (11)

Nervous

Respiratory

Urinary

Reproductive

Cardiovascular/circulatory

Lymphatic/immune

Muscular

Skeletal

Endocrine

Integumentary

Digestive

Digestion

Process by which food is broken down into smaller pieces that can be absorbed by the body

What are the small units that can be absorbed (from each macronutrient)?

Sugars (from carbs)

Amino acids (from proteins)

Fatty acids (from lipids)

GI tract

Gastrointestinal tract (a.k.a. digestive tract; gut) = hollow tube that runs from the mouth to the anus (about 30 ft)

Lumen

Opening inside the GI tract through which material can pass

Mucosa and mucosal cells

Layer of tissue that lines the lumen (contains many mucosal cells)

• mucosal cells only live for 2-5 days

• new cells formed continuously to replace the previous

• the mucosa has high nutrient needs; one of the first parts of the body affected by nutrient deficiency

Transit time

Time it takes food to travel the length of the GI tract from mouth to anus

What are the accessory organs in the digestive system? Briefly describe what they do. (4)

Salivary glands–produce saliva (which have a starch-digesting enzyme)

Liver–makes bile (aids digestion and absorbtion of fat)

Gallbladder–stores bile and releases it into the small intestine when needed

Pancreas–releases bicarbonate to neutralize intestinal contents; enzymes that digest carbs, protein, fat

The two ways the mouth aids in digestion

Mechanical

• teeth crush and grind large pieces into smaller pieces

• saliva and beverages help moisten food so you can swallow

Chemical

• saliva is rich in enzymes that help break down carbs and fats at the chemical level

• starches and large fats are being broken down into smaller pieces

Digestive system secretions (3)

Mucus–viscous fluid secreted by glands to lubricate, moisten, and protect cells from harsh environments; secreted from mucosal cells lining the digestive tract

Enzymes–protein molecule that speeds up chemical reactions, helping break down larger molecules into smaller ones

Hormones–chemicals secreted from cells which travel through the bloodstream to signal to cells in another part of the body

What is an important enzyme in saliva? What is a non-digestive benefit of saliva?

Salivary amylase = begins chemical breakdown of carbohydrates

Saliva also helps wash away bacteria that can cause tooth decay (prevent cavities)

Name for a mouthful of food that has been swallowed

Bolus

What are the first parts of the body involved in swallowing? Functions?

Pharynx–short tube that connects the mouth with the esophagus

Epiglottis–the bolus closes off your epiglottus down so it can close off your air passages so you don’t choke while swallowing; after swallowing, returns to original position

Esophagus

Tongue

Name for the rhythmic muscle contractions that move bolus down the esophagus

Peristalsis

What controls the movement of food from the esophagus to the stomach?

Gastroesophageal sphincter

What does GERD stand for? What causes it? What is the momentary version of it called?

Gastroesophageal Reflux Disease (chronic)

Occurs with leakage past the gastroesophageal sphincter (back up)

Heartburn is the momentary version

What leaves the stomach to enter the small intestine through what sphincter? How does the stomach know to empty?

Chyme

Pyloric sphincter

Emptying of the stomach regulated by signals from the small intestines; affected by meal sizes

The three muscle layers of the stomach; what makes the last special?

Longitudinal

Circular

Diagonal–allows for the powerful contractions that churn and mix stomach contents

Functions of hydrochloric acid (3); what protects the stomach from it?

Kills potential pathogens, activates pepsin, inhibits amylase activity

Mucosa prevents HCl from burning the stomach

Steps in the regulation of stomach motility and secretion

1) before food enters stomach, the sensory anticipation of food causes the brain to send nerve signals that stimulate gastric secretions and increase rate of stomach motility

2) food entering stomach increases gastric secretions and motility further by stimulating local nerves, sending signals to the brain, and stimulating secretion of gastrin

3) food leaving stomach distends the small intestine, triggering hormonal and nervous signals that decrease stomach motility and slow secretion of gastric juice

Explain the lining of the stomach (parts of the anatomy)

Lining covered by gastric pits. Inside the pits are gastric glands, which are made up of different types of cells that the produce the mucus, hydrochloric acid, and inactive form of pepsin that make up gastric juice.

When is pepsin activated? Why must this happen?

Activated when protein comes into contact with the HCl in the stomach. This is necessary because protein cannot be broken down by salivary amylase in the mouth.

Where does the majority of digestion occur?

Small intestine

What covers the inner surface of the small intestine?

Villi–finger-like projections. Each villus contains a capillary and a lacteal (small lymph vessel).

• nutrients only have to cross the single-cell layer of the mucosa to reach the blood or lymph so it may be delivered to the rest of the body

What is each villus covered with?

Microvilli–tiny projections of the mucosal cell membrane. Some digestive enzymes produced by small intestine are located in the microvilli membrane, and some in the mucosal cells

What two things are added/secreted into the small intestine?

Pancreatic juice and bile

What does pancreatic juice consist of?

Sodium bicarbonate–neutralizes chyme; literally baking soda

Pancreatic amylase–converts polysaccharides into monosacch.

Pancreatic protease–converts polypeptides into amino acids

Pancreatic lipase–converts triglycerides into fatty acids and glycerol

What is the relationship between the liver and gallbladder?

Liver makes bile and the gallbladder stores it to later secrete it.

Bile

An emulsifier (breaks up fat droplets so lipases can access molecules and complete digestion)

Explain the absorption of carbs in the small intestine

• Pancreatic amylase digests starch into double sugars or short glucose chains

• Fiber passes to the large intestine as it cannot be digested by human enzymes

• Enzymes in the microvilli digest double sugars into single sugars which are then absorbed into the blood

Explain the absorption of long amino acid chains in the small intestine

• Pancreatic proteases (plus proteases in mivrovilli) digest them into amino acids and short amino acid chains

• Amino acids are absorbed into the mucosal cells where they are digested into single amino acids, which then pass into the blood

Explain the absorption of large lipid droplets in the small intestine

• Bile divides large fat globules; pancreatic lipases digest fat molecules into fatty acids

• Short chain fatty acids absorbed by the mucosal cells and pass directly into the blood

• Long chain fatty acids combine with bile to form small droplet that aid in the absorption of fatty acids and other fat-soluble substances into the mucosal cell

• Absorbed lipids are incorporated into transport particles that pass into the lymph; they enter the blood without first passing through the liver

Diffusion

Net movement of substances from an area of higher concentration to lower concentration

Simple diffusion

The unassisted diffusion of a substance across a cell membrane

Osmosis

The unassisted diffusion of water across a cell membrane

• from an area of lower concentration of dissolved substances to higher concentration of dissolved substances

Facilitated diffusion

Assisted diffusion of a substance across a cell membrane

• requires help from a carrier molecule

Active Transport

The transport of substances across a cell membrane with the aid of a carrier molecule and the expenditure of energy

• allows for transportation of substances from an area of lower concentration to higher

• (e.g. amino acids to be absorbed, even though they are present in higher concentrations in the mucosal cell than in the lumen)

What makes up the large intestine and how long is each part?

Colon (5 ft) and rectum (8 inches)

Key things that happen in the colon

Contributes to absorption of water and some vitamins and minerals

Peristalsis occurs more slowly here, which favors the growth of intestinal microbiota

Water, nutrients, and fecal matter may spend 24 hours in the colon

Primary function of the rectum

Stores feces

Feces (composed of?)

Undigested, unabsorbed matter, dead cells, secretions from the GI tract, water, and bacteria

Key events in the small intestine (3)

Sodium bicarbonate neutralizes chyme; baking soda

Pancreatic enzymes digest food

Bile breaks up fat

Metabolic pathway

The series of biochemical reactions needed to go from a raw material to the final product

• chemical energy is a form of energy stored in the bonds that hold molecules together

• when those bonds are broken, the energy that is released can be converted into a form that the body can use

What is the energy-carrying molecule that the body uses as fuel?

Adenosine triphosphate (ATP)–the bonds between the three phosphate groups are very high in energy, which is released when the bonds are broken

How do the two types of reactions relate to ATP?

Nutrients can be used in catabolic reactions to produce ATP

Nutrients can be used in anabolic reactions that utilize ATP to synthesize molecules needed by the body

Catabolic vs. anabolic reaction

Catabolic when aiming to break down one large molecule into smaller, simpler ones

• requires one molecule of water (uses one up; hydrolysis)

• releases ATP

Anabolic when aiming to build larger, complex molecules out of simpler ones

• requires ATP

• releases one molecule of water (called condensation)

LEOGER

Lose electron–oxidized

Gain electron–reduced

Oxidized

When a compound loses an electron or undergoes a chemical reaction with oxygen

Reduced

Refers to a substance that has gained an electron (think “reducing” the charge)

What is a free radical and why are they bad? How to neutralize?

An atom or molecule with one or more unpaired electrons; unpaired electron makes molecule unstable and destructive to nearby molecules

Neutralize with antioxidants! (Vitamin E can donate an electron to electron-scavenging molecules. Vitamin C can resupply the vitamin E.)

Function of microbes

Act on unabsorbed foods to produce nutrients used by the bacteria

Maintain mucosal layer lining the intestines

• serve as barrier

• modulate inflammation in gut

• prevent growth of disease-causing bacteria

Assist in maturation of immune system

Effects of a less diverse microbiota

Unable to maintain balance between beneficial and harmful bacteria

Implicated in development of intestinal diseases

Prebiotic

A substance that passes undigested into the colon and stimulates the growth and/or activity of certain types of bacteria

Probiotic

Live bacteria that, when consumed, live temporarily in the colon and confer health benefits on the host

Allergic reaction

When immune system produces antibodies to an allergen

Antibodies

A protein, released by a type of lymphocyte, that interacts with and neutralizes specific antigens

Antigens

A foreign substance that stimulates an immune response

Autoimmune disease

When the body’s immune system attacks its own tissues

Celiac disease

Immune response to gluten–triggers an immune response that damages the villi of the small intestine

Ulcer

Damage to the lining of the GI tract due to stomach acid or pepsin

Gallstones; how to treat?

Solid material accumulates in gallbladder/bile ducts and blocks bile

Usually treated by removing gallbladder, after which bile drips directly from the liver to the intestines

When does diarrhea occur

When substances move too quickly through the colon for water to be absorbed, or if water is drawn out from cells into the lumen of the intestine

Causes of constipation

Too little water, fiber, or exercise

• also decreased strength of large intestinal muscles, disease, or medications

How to reduce heartburn

Eating appropriate amounts

Taking breaks between meals

Staying upright after eating

Drinking water with/between meals

Delivering nutrients with cardiovascular and lymphatic system (3)

1) water-soluble nutrients absorbed into capillaries; fat-soluble nutrients absorbed into lacteals

2) blood from digestive system enters portal circulation to first travel to liver

3) liver detoxifies and nutrients can be sent to cells or stored

Pulmonary circuit

Heart pumps blood to lungs to remove CO₂ and pick up oxygen

Systemic circuit

Heart pumps blood to body and tissue cells to deliver oxygen and pick up CO₂

Tell the story of blood circulation (6)

1. oxygen poor blood that reaches heart gets pumped to lungs

2. capillaries in lungs pick up oxygen and release CO₂ to be exhaled

3. oxygen rich blood travels from lungs back to heart through veins

4. heart pumps blood to rest of body via arteries

5. capillaries in other areas of body distribute nutrients and oxygen to tissues and pick up CO₂

6. oxygen poor blood returns to heart via veins

Liver functions (3)

Gatekeeper between body and substances absorbed by intestines

• Determines whether nutrients are stored or delivered immediately

• Enzyme systems that protect body from toxins absorbed in the GI tract

• Role in synthesis and breaking down of amino acids, protein, lipids

Hepatic portal vein

Carries molecules from intestine to liver

Functions of lymphatic system (3)

Absorbs fat-soluble nutrients

Removes fluids from tissues to prevent swelling

Contains immune cells to fight infection

Ways that the body eliminates waste (4)

Feces–undigested food particles

Lungs–CO₂ and some water

Skin–minerals, some water, nitrogen-containing waste

Urine–metabolic waste, excess water, salts

What is required to create energy in the body and what is released after the conversion?

Cellular respiration uses oxygen to convert fatty acids, glucose, and amino acids into carbon dioxide, water, and ATP (for energy)

Process of producing ATP (3)

1) with oxygen [the big 3] are metabolized to produce a two-carbon molecule (acetyl-CoA)

2) acetyl-CoA enters citric acid cycle that produces two molecules of CO₂

3) most of the energy released from the big 3 are released to produce ATP; oxygen combines with hydrogen to form water

→ POP QUIZ what kind of reaction is this?