BIOL216 Exam 4 - GI

metabolism

the biochemical reactions that allow a cell or organism to extract energy from its surroundings and use that energy for homeostasis, growth, and reproduction

organic molecule (functions)

• provide E

• building blocks for making complex biological molecules

monosaccharide

• smallest kind of sugar molecule, a simple sugar, a single unit sugar, building blocks of more complex sugar

• main fuel that cells use for cellular work

sugar

characterized by several hydroxyl groups (-OH) and a carbonyl group (>C=O); diff types are isomers

monsaccharides form…

rings, in aqueous solutions

disaccharide

two monosaccharides linked via dehydration reaction

• ex: sucrose, lactose, and maltose

sucrose =

glucose + fructose

lactose =

glucose + galactose

maltose=

glucose + glucose

polysaccharides

polymers of monosaccharides, long chains of sugar units

• ex: starch, glycogen, and cellulose

starch

long chain of glucoses, found in plants

glycogen

long chain of glucoses but with branches, found in animals

cellulose

long chain of glucoses but with different linkage, found in cell walls of plants (structural)

• most abundant organic compound on Earth

• forms cable-like fibrils in the tough walls that enclose plants

• major component of wood

• also known as dietary fiber

lipids

consists mainly of C and H atoms linked by nonpolar, covalent bonds — so, mostly hydrophobic and insoluble in water

• fats, phospholipids, steroids

fats

dietary fat, mostly composed of triglycerides

• made from glycerol + three fatty acids

function of fat

energy storage, cushioning, insulation

unsaturated fats

not fully saturated with H’s so has some double bonds that cause bend in FA chain

saturated

fully saturated with H’s

triglycerides with unsaturated fatty acids

• tend to be liquid at room temp (oil) b/c their shape makes it harder for them to stack

• lower melting point

• most plant, some fish triglycerides

triglycerides with saturated fatty acids

• tend to be solid at room temp because they can easily stack

• most animal triglycerides 

• high saturated FA diet → atherosclerosis

monounsaturated fats

single double bond in their fatty acids

polyunsaturated fats

have two or more double bonds in their fatty acid

• ex: trilinolein

plant fats

unsaturated (oils)

animal fats

saturated (lard…?)

atherosclerosis

plaque builds up in the walls of blood vessels → leads to heart attack/stroke

• plaque → reduced blood flow → heart attack/stroke

essential nutrients

• essential amino acids

• essential fatty acids

• essential minerals

  • vitamins

essential amino acids

methionine

tryptophan

leucine

phenylalanine

threonine

valine

isoleucine

lysine

vitamins

organic molecules required in small quantities that an animal can’t synthesis for itself

water-soluble vitamins

non-protein organic subunits that associate with enzymes to aid in catalysis

vitamin b2

riboflavin - converted into FAD to assist in catalysis

niacin

vitamin converted into NAD+ to assit in catalysis

fat soluble vitamins

have a variety of special roles

• ex: vitamin A = visual pigments

functions of minerals

ions: excitability of neurons, cardiac muscle contraction

• ex: Na+, K+

structural material

• ex: calcium in bones

parts of other molecules

• ex: iron in hemoglobin

mouth, pharynx, esophagus

food begins its travel through the digestive system here

stomach

stores food and continues digestion, muscular sac

• stretches to store food

• secretes mucus and gastric juice

small intestine

completes digestion and begins absorption of nutrients

• duodenum receives secretions from liver, gallbladder, and pancreas 

• produces enzymes that complete digestion of proteins, carbohydrates, and nucleic acids

• nutrients absorbed here are mostly processed in liver

large intestine

mainly absorbs water and mineral ions from digestive residues

• secretes mucus and bicarbonate ions

• concentrates undigested matter into feces

all mammals have…

mouth, pharynx, esophagus, stomach, intestine, anus

sphincter

rings of smooth muscle form valves between major regions of the digestive tract

mouth

entrance to system

• food is moistened and chewed

• polysaccharide digestion begins

pharynx

muscular contractions move food to esophagus using swallowing reflux

esophagus

muscular, mucus moistened tube moves food from pharynx to stomach

salivary glands

secrete saliva

saliva

contains lubricating mucus, amylase, lysozyme, and bicarbonate ions

amylase

starch digesting enzyme

lysozyme

enzyme that kills bacteria

rectum

stores feces

• distension stimulates expulsion of feces

liver

secretes bile and bicarbonate ions

bile

emulsifies fats

gallbladder

stores and concentrates bile secreted by liver

pancreas

secretes enzymes that break down all major food molecules and bicarbonate ions 

enzymes secreted by pancreas

proteases, amylases, lipases, nucleases

bicarbonate ions secreted by pancreas

neutralize (acidity) pH of chyme for optimal activity of amylase, proteases, lipase, nucleases

anus

end of digestive system

• opening through which feces are expelled

lower esophageal sphincter

between esophagus and stomach

pyloric sphincter

between stomach and small intestine

layers of vertebrate gut

mucosa, submucosa, muscularis, serosa

mucosa

lines inside of gut

• contains epithelial cells and glandular cells

epithelial cells in mucosa

absorb nutrients and seal off digestive contents from body fluids

glandular cells

secrete enzymes, mucus, pH regulation

submucosa

• made of elastic connective tissue

• neuron network: local control of digestive activity

• blood and lymph vessels

muscularis

formed by circular layer and longitudinal layers to push contents through gut 

oblique layer

layer of muscularis in only the stomach

serosa

outermost layer of the gut

• made of connective tissue that is continuous with mesentary

• secretes lubricating fluid to reduce friction between digestive organs and other organs

mesentary

tissue that suspends digestive organs in the abdomen

circular muscle

constricts gut diameter

longitudinal muscle

shortens and widens gut

peristalsis

coordinated contractions of circular and smooth muscles produce peristaltic waves that move digestive contents from mouth to anus

chyme

partially processed food during peristalsis

teeth

break food into smaller bits

bolus

food mass that is swallowed

epiglottis

flap of tissue at base of tongue that keeps food from going into the trachea

glottis

middle part of larynx - area where vocal cords are located

sealing nasal passages during swallowing

soft palate elevates to prevent food from entering nasal passage

sealing mouth during swallowing

tongue pressure seals back of mouth to prevent bolus from coming back up

sealing trachea during swallowing

larynx moves upward → pushes glottis against epiglottis to prevent bolus from entering trachea

gastric juice consists of…

• hydrochloric acid

• pepsin

• mucus (secreted by glandular cells)

• parietal cells

parietal cells

secrete H+ and Cl-

chief cells

secrete pepsinogen (precursor for pepsin)

• hydrochloric acid breaks pepsinogen down into pepsin

gastric pit

indentations in the mucosa layer of the stomach lumen

gastric pit cells

surface epithelial cells, mucous cells, chief cells, and parietal cells

gastrin

major hormone that regulates acid secretion in the stomach

gastrin

major hormone that regulates acid secretion in the stomach

• stimulated by stomach distension, presence of digested proteins

stomach environment

ph = 2; acidic and optimal for pepsin

• helps unfold proteins so they can be broken down

• kills unwanted bacteria

  • stomach’s mucus protects stomach wall from acidity and breakdown from pepsin

stomach’s digestive properties

• takes 1-6 hours to empty after a meal

• food is not moved along faster than it can be digested

fat’s digestive process

digested in small intestines and more slowly than other nutrients to ensure that further emptying of the stomach is prevented until fat is processed (regulates how fast food enters the small intestine)

what is digested in small intestine

proteins, polysaccharides, triglycerides, nucleic acids

proteins digested by

endopeptidases and exopeptidases

polysaccharides digested by

hydrolyzed by amylase, then disaccharides

triglycerides digested by

lipase

nucleic acids

hydrolyzed by nucleases (DNase, RNase)

small intestine role in digestive process

absorption of nutrients begins

• contains microvilli and intestinal villi for absorption

intestinal villi

folds in lining of small intestine, increase surface area for absorption

microvilli

projections of plasma membrane of epithelial cells to increase surface area of intestine for absorption

brush border

makeup of microvilli on surface of intestinal epithelial (mucosal) cell

lacteal

lymphatic vessels of the small intestine that absorb digested fats

how does the pancreas help the digestive process

secretes digestive enzymes and bicarb ions into ducts that empty into duodenum

pancreas releases basic fluid containing

• high concentration of bicarbonate ions

• trypsin

• chymotrypsin

• carboxypeptidase

• lipase

• amylase

• nuclease

glucagon

alphae cells

• released when glucose levels are low

• makes liver convert stored glycogen into glucose and release into bloodstream to raise glucose levels

insulin (beta cells)

• causes cells in liver, muscle, and fat tissue to take up glucose from the blood

• sends signal to store glucose as glycogen in liver and muscle, and to stop using fat as an energy source