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atom
smallest unit of matter; most are neutral
element
substance made from 1 type of atom
valence electrons
outermost electrons in atom that interact with other atoms, often losing, gaining, or sharing electrons in bonds
compound
substance formed by the chemical combination of more than 2 elements that are chemically bonded
chemical bonds
lasting attraction between atoms, ions, or molecules that enables them to form chemical compounds
ionic bonds
2 ions bond because of opposite charges
ion
molecule that has gained or lost an electron and has a charge
covalent bond
atoms share electrons
molecule
group of covalently bonded atoms
polar covalent bond
unequal share of electrons, leads to partial charges
nonpolar covalent bond
equal share of electrons
electronegativity
the pull on shared valence electrons
hydrophilic
water soluble (polar molecules and ionic compounds)
hydrophobic
avoids water (nonpolar molecules, fats & lipids)
metabolism
the sum of all reactions occurring in a cell or organism
catabolism
nutrients or cell constituents are broken down to release energy or components (hydrolysis)
anabolism
larger molecules built or made from 2 or more atoms, ions, or molecules (dehydration synthesis)
ATP
energy transfer molecule with 3 phosphates
ADP
the low energy version of ATP, has 2 phosphates
organic compound
molecule with chains or rings of carbon
macromolecule
large molecule
polymer
long molecule made of many similar building blocks
monomer
small building blocks making up polymers
carbohydrates
source of energy, water balance, secretion; sugar monomer; water soluble; CHO
lipids
energy storage, insulation, waterproofing, hormones; glycerol/fatty acid monomer; not water soluble; CH(O)
proteins
structures, reactions, transport, hormones, movement; amino acid monomer; sometimes water soluble; CHONS
nucleic acids
holds genetic information, makes proteins; nucleotide monomer; water soluble; CHONP
saturated fats
no double bonds between carbons, solid at room temperature
unsaturated fats
at least 1 double bond between carbons, liquid at room temperature
phospholipids
hydrophilic (polar) head and hydrophobic (nonpolar) tail
steroid
fused rings form of lipids used as hormones or in membranes
cholesterol
used for membranes, modified into other hormones and vitamin D
hormones
signal molecules that travel via blood
enzymes
catalyst; proteins that speed up chemical reactions
activation energy
amount of energy required to start a reaction
substrate
reactant that enzyme acts on and changes
denaturation
enzyme shape changes causing it to not work on a reaction
inhibition
slows and disrupts enzyme work
activation
improves enzyme work temporarily
buffers
materials that prevent pH changes; needed for pH homeostasis
coenzyme
helps enzyme work better; “on switch”
inhibitor
blocks enzyme from doing a reaction, “off switch”
reaction rate
how fast the enzyme changes the substrate
active site
specific region on enzyme where substrate binds and catalysis takes place
ingestion
taking in food to the digestive tract
digestion
breaking down food into simpler molecules
absorption
bring nutrients from digested material to the blood (or lymph) to be delivered to cells
elimination
removal of undigested materials from body via defecation
defecation
feces
secretion
release of enzymes and chemicals material to facilitate digestion, or hormones to regulate digestion
motility
muscular movement of materials through GI tract
regulation
coordinating digestive organ activity
alimentary canal (GI tract)
organs that digested food passes through, the “tube” for food; mouth, pharynx, esophagus, intestines, stomach
accessory organs
organs that contribute to the digestive process in the main alimentary canal organs; teeth, salivary glands, liver, gallbladder, pancreas
mechanical digestion
physical breaking down of food into smaller pieces to increase surface area of food for exposure to chemical digestion
chemical digestion
chemical reactions assisted by enzymes that break chemical bonds in the macromolecules to make them smaller (monomers) to be absorbed into blood
mucosa
protective inner layer that produces mucus (thick in the stomach) and provides a barrier against foreign particles and captures them in mucus and clears them out
submucosa
layer that is made of connective tissue and contains blood, nerves, and lymph vessels
muscularis
layer of smooth muscle that is important for peristalsis
serosa
outermost layer of the wall
mesentary
special peritoneal membranes that line the cavity and anchors digestive organs to the abdominal cavity
sphincter
muscular doorway between GI tract organs to control when things enter or exit
lower esophageal sphincter
(cardiac) prevents stomach acid from entering esophagus (involuntary)
pyloric sphincter
controls when stomach contents enter duodenum (involuntary)
anal sphincter
controls exit of feces from body (involuntary/voluntary)
mouth
used to take in food
mastication
chewing food and mixing in saliva and its enzymes (amylase and some lipase) from salivary glands
bolus
ball like mix of saliva and food that will be swallowed
pharynx
“throat” that leads from mouth and nose to esophagus or trachea
epiglottis
flap of tissue at end of pharynx/throat that blocks off trachea (windpipe) to make sure food goes into esophagus
esophagus
moves bolus of food from mouth to stomach
peristalsis
rhythmic wavelike contraction of muscles that helps push food forward in GI tract
segmentation
breaking of food by “swishing” from similar peristalsis-like contraction of muscles in GI tract
stomach
allows chemical and mechanical digestion through gastric juices and churning; can briefly store food from large meals
chyme
liquid mix of gastric juices and food (from bolus)
gastric juices
mix of enzymes, acids, and hormones made by stomach
hydrochloric acid
kills bacteria, creates acidic pH of 2-4, activates stomach enzymes
pepsin
enzyme made by stomach that digests proteins in the stomach
gastrin
hormone in stomach that regulates digestion
churning
strong movement of stomach contents by muscles
rugae
folds in the stomach that allow it to expand
small intestine
key organ that does majority of chemical digestion and nutrient absorption in the body
duodenum
initial segment of small intestine leading from stomach, receives enzymes and chemical from gallbladder and pancreas
villi
finger-like projections lining intestines that increase surface area for absorption into blood vessels
large intestine
absorbs remaining water and helps form feces, has bacteria that help release vitamins
feces
POOP
microbiome
beneficial bacteria communities that help release nutrients, such as vitamin K and B
appendix
contains bacteria that replenish intestinal flora
rectum
stores feces at the end of the large intestine
anus
opening allowing elimination of feces from body
fundus
dome shaped “hump” at the top of the stomach, located inferior to the diaphragm and to the left of the cardia
pylorus
funnel-shaped “end” of the stomach that connects the stomach to the duodenum
lumen
hollow space in the middle of an organ, lined by the mucosa in the GI tract
gastric pits
dots on the internal surface of the stomach, makes digestive gastric fluid
teeth
helps with mastication in mouth and used for grinding and tearing food
salivary gland
produces saliva that is secreted into mouth to soften food (amylase + very little and ineffective lipase)
amylase
starts breakdown of carbohydrate starches in the mouth and duodenum, produced by pancreas and salivary glands
lipase
digests lipids (fats) but needs bile, digests very little in mouth and mostly in duodenum, produced by salivary glands and pancreas
bile
critical secretion that helps emulsify fat; produced in liver and stored in gallbladder
emulsification
helps cut fat globs separate into smaller droplets so it can be accessed by digestive enzymes in the small intestine