6.1 - 6.2 Inquiry into Biology (Bio 20)

Homeostasis

* The dynamic constancy of the internal environment
* is a dynamic equilibrium (always fluctuating)
* if the part of our body is concerned w/ reproduction it is most likely concerned w/ homeostasis
* to maintain a constant internal environment our body has sensors that measure each condition. the sensors constantly monitor these conditions and relay them to a control centre (often a region of the brain or spinal cords but can also be endocrine glands)
* the control centre receives messages from several sensors and then determines whether the value of the condition is deviating from the set point.
* when deviation occurs (stimulus), the integrating centre sends a message to increase or decrease the activity of particular effectors
* effectors are usually muscles or glands and can change the value of the condition in question back to the “set point” (response)
* negative feedback loops maintain a state of homeostasis by correcting deviations form a set point.
* ie) a sensor detects a change that disrupts a balanced state and signals a control centre. the control centre then activates an effector which reverse the change and restores the balanced state

Nucleic Acids

function:

1) direct cell growth & department of cells

2) expression and transfer of genetic code

subunit: nucleotides (4 different types)

types of nucleic acids:

* RNA: ribonucleic acid - involved in the making of proteins
* DNA: deoxyribonucleic acid: in the nucleus, contains genetic info for building cells/protein

Lipids

function:

1) phospholipid bilayer (cell membrane)

2) energy storage → butter, oil, lard (fats&oils)

3) steroids → form sex hormones (estrogen&testosterone)

subunit: 3 fatty acids & glycerol

saturated fatty acids: do not have any double bonds between any carbons (solid at room temp)

unsaturated fatty acids: at least one double bond between the carbons (liquid at room temp)

* add drop on paper and if it doesn’t absorb completely and is translucent then lipids are present

Proteins

function:

1) used in muscle, transport, (carrier proteins), antibodies, etc…

2) make up most cellular structures

subunit: amino acids

* 20 amino acids; 11 are synthesized by the body but 9 must come from your diet
* add biuret reagent (blue) and if colour changes to violet proteins are present and if it changes to pink peptides are present

Carbohydrates

* types of carbohydrates

1) monosaccharides: one simple sugar, eg. glucose

2) disaccharides: two simple sugars, eg. maltose

3) polysaccharides: many linked simple sugars
* starches: energy in plants
* glycogen: animals energy
* cellulose: used iin the cell wall of plant cells
* add iodine solution and if sample changes to blue/black carbohydrates are present
* subunits: sugars, polymers of glucose
* function: energy storage
* eg. of macromolecules: suagrs, starches, and glycogen

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Vitamins & Minerals

* are not macromolecules
* are essential tot he structure and function of all cells
* only needed in small amounts
* vitamins: organic compounds. functions include - coenzymes, used for tissue development, & growth
* minerals: inorganic compounds, functions include - chemical reaction, bones, hemoglobin, & hormones

Sugars (mono/disaccharides)

* add benedict’s solution to the sample
* green: very low
* yellow: low
* yellow/orange: moderate
* orange: high
* red/orange: very high

Dehydration Synthesis

* removes water from 2 or more subunits to make a macromolecule
* to form a bond between subunits, an ‘H’ and an ‘OH’ are removed from the subunits to form water, & the subunits bond together
* Removes H2O and H2O is a product

Hydrolysis

* breaks the covalent bonds in macromolecules by adding water
* a molecule of H2O us added, one ‘H: bonds to one subunit & ‘OH’ bonds to another

Simple Sugars & Polysaccharides

simple sugars: a carbohydrate molecule with three to seven carbon atoms (and the corresponding # of hydrogen and oxygen atoms) - this is called a monosaccharide and a disaccharide is two of these

polysaccharides: a complex carb that consists of many linked simple sugars

* starches (energy in plants)
* glycogen (energy in animals)
* cellulose (used in the cell wall)

Macromolecules

a large, complex assembly of organic molecules; four categories of macromolecules are carbs, lipids, proteins, and nucleic acids

Peptide bonds

bond between the amino group of one amino acid and the carboxyl group of another protein

Catalysts

A chemical that speeds up a chemical reaction but is not used up in the reaction.

* does not increase temperature and can be recovered unchanged when the reaction is complete
* function by lowering the amount of energy needs to initiate a reaction.

Enzymes

A protein molecule that acts as a catalyst to increase the rate of a reaction is called an enzyme.

* enzymes have a 3d shape that is specific to the kind of reactant with which it can combine
* the enzyme physically fits with a specific substrate-its reactant molecule.

Accessory Organs

Structures that aid digestion but don’t contain food

* Salivary Glands


* Liver
* Gall Bladder
* Pancreas

The Digestive Tract

Organs that contain the food

* Mouth
* Esophagus
* Stomach
* Small Intestine
* Large Intestine
* Rectum
* Anus

Salivary Glands

* secrete starch-digesting enzymes
* produce saliva → a mix of water & enzymes = amylase (starch → smaller carbs)
* the water in the saliva moistens food and activates taste buds
* amylase: (enzyme) polysaccharides into disaccharides

Mouth

* teeth + tongue = mechanical digestion
* bolus: a mix of food and saliva

Esophagus

* long muscular tube, the bolus stretches the esophagus; stimulates peristalsis (wave-like) muscular contractions .: pushes the bolus towards the stomach

Stomach

* muscular bag, rhythmic contractions. mixes bolus w/ stomach acid + enzymes (gastric juices) creating CHYME
* lined w/ mucus (or mucous) protecting it from the gastric juices

Small Intestine

* complete digestion
* pH of 9
* 90% of absorption → villi and microvilli, which increase surface area
* contains 3 sections
* duodenum: digestion & absorption
* jejunum: absorption
* ileum: absorption
* Secretin: (hormone) - stimulates the pancreas and gall bladder
* Enterkinase: converts trypsinogen into trypsin

\-secretes enzymes that digest macromolecules; absorbs hydrolyzed molecules into bloodstream

Large Intestine

* approx. 1.5m in length w/ a wider diameter
* function: concentrate and eliminate waste by

1) absorbing H20 + salt into the blood

2) bacteria: use waste material to make vitamins (K + B12); break it down further

3) form and expel feces (cellulose & fibre)

\-absorbs water and salts; passes remaining undigested material and some water out of the body

Rectum

* Can hold on to the feces when you pass gas
* stores waste prior to elimination

Anus

* Releases the feces, controlled by the 2 sphincters (one can be consciously control and one is controlled by the nervous system)
* Holds rectum closed; opens to allow elimination

Pancreas

\-Releases bicarbonate ions (HCO3), neutralizes the gastric juices and increases the pH and also has lots of enzymes

\-Manufactures enzymes to digest macromolecules; secretes bicarbonate to neutralize stomach acid that enters the small intestine

* releases pancreatic juices into the small intestine
* pancreatic juices include:
* Bicarbonate Ions: neutralizes
* Lipase: (enzyme) - breaks down fats
* Trypsinogen: becomes trypsin peptides into shorter chains of amino acids
* Erepsin: short chains of amino acids into amino acids
* disaccharase: disaccharides into monosaccharides

Gall Bladder

Stores bile and releases it into the small intestine

Liver

* stores glycogen
* secretes bile salts
* emulsifies fats/lipids: taking large fat droplets and breaking it into smaller droplets; to increases surface area
* Release bile which emulsifies fats (physical digestion)

Pharynx

opening at the back of the mouth to the trachea (wind pipe) & esophagus

Epiglottis

closes the trachea when swallowing food

Salivary Amalyse

* Salivary amylase is a glucose-polymer cleavage enzyme that is produced by the salivary glands.

Bile

Bile is a fluid that is made and released by the liver and stored in the gallbladder. Bile helps with digestion. It breaks down fats into fatty acids, which can be taken into the body by the digestive tract.

Gastrin

* a hormone
* in the stomach
* secreted by the stomach into the blood to stimulate the release of gastric juices and muscle contractions

Protease

* in the small intestine

Carbohydrase

* sucrase
* maltase
* lactase
* in the small intestine

CCK

Esophageal & Pyloric Sphincter

* esophageal sphincter is a door way that comes b4 the stomach
* pyloric sphincter comes after the stomach

Appendix

* ? may have good bacteria or involved with immune system

Mechanical & Chemical Digestion

Mechanical: physical breakdown (eg. chewing)

Chemical: chemical breakdown (ie. hydrolysis)

Gastric Juices

* HCL: kills any microbes; activates pepsinogen
* Pepsinogen: reacts w/ the HCL to become pepsin
* Pepsin: enzyme (protein → peptides)
* Rennin: coagulate milk protein (slows down the movement)

Salivary Amylase

* enzyme acts in the mouth
* pH = 7
* substrate (food) digested: starch and glycogen
* products of digestion: maltose (disaccharide)
* origin of enzymes: salivary glands

Pancreatic Amylase

* enzyme acts in the small intestine
* pH = 8
* substrate (food) digested: starch and glycogen
* products of digestion: maltose
* origin of enzymes: pancreas

Carbs (sucrase, maltase, lactase)

* enzymes act in the small intestine
* substrate (food) digested:
* sucrase - sucrose
* maltase - maltose
* lactase - lactose
* products of digestion:
* sucrase - glucose + fructose
* maltase - glucose
* lactase - glucose + galactose
* origin of enzymes: small intestine

Pancreatic lipase

* enzymes act in the small intestine
* pH = 8
* substrate (food) digested: lipids
* products of digestion: fatty acids and glycerol
* origin of enzymes: pancreas

Proteases (pepsin, trypsin, chymotrypsin)

* where enzyme acts:
* pepsin - stomach (pH = 1-2)
* trypsin & chymotrypsin - small intestine (pH = 8)
* substrate (food) digested:
* pepsin - protein
* trypsin & chymotrypsin - peptides
* products of digestion:
* pepsin - peptides
* trypsin & chymotrypsin - smaller peptides
* origin of enzymes:
* pepsin - stomach
* trypsin & chymotrypsin - pancreas

peptidases

* enzymes act in the small intestine
* pH = 8
* substrate (food) digested: peptides
* products of digestion: smaller peptides and amino acids
* origin of enzymes: pancreas and small intestine

Nucleases

* enzyme acts in the small intestine
* pH = 8
* substrate (food) digested: nucleic acids
* products of digestion: nucleotides and components
* origin if enzymes: pancreas

Nucleosidase’s

* enzyme acts in the small intestine
* pH = 8
* substrate (food) digested: nucleotides
* products of digestion: bases, sugars, and phosphates
* origin of enzyme: small intestine

Small Intestine (macromolecules)

* Complex Carbs: Polysaccharides and Disaccharides (Carboghydrases: pancreatic amylase, sucrase, maltase, and lactase)\] → Monosaccharides
* Proteins: Smaller peptides {Proteases: trypsin & chymotrypsin} → Peptides {Peptidases} → Amino acids
* Fats: fat droplets {bile} → fat droplets(emulsified) {Lipases} → Glycerol and fatty acids
* Nucleic Acids: DNA and RNA {Nucleases} → Nucleotides {Nucleosidase’s} → Nitrogen-containing bases, sugars, and phosphates

Organic Molecules

* always contain carbon and hydrogen
* the chemistry of carbon accounts for the formation of the very large variety of organic molecules found in living things

Enzyme Function

Factors affecting enzyme activity

Absorption of Glucose in the SI

starch (polysaccharide) → enzyme → disaccharide → enzyme → glucose (monosaccharide) → active transport into cells on intestinal wall → blood vessel

* starts in the mouth w/ salivary amylase
* hydrochloric acid denatures so digestion stops
* chyme enters small intestine & pancreatic amylase completes digestion of starch in2 disaccharides
* other carbohydrases hydrolyze the disaccharides in2 monosaccharides
* monosaccharides absorbed via active transport in2 villi to enter blood stream then to the liver then to all body cells

Absorption of Amino Acids in the SI

Proteins → enzymes → peptides → amino acids → active transport into cells of intestinal wall → blood vessel

\[using protein enzymes\]

* in the stomach, pepsin breaks proteins into polypeptides
* the polypeptides are broken down by trypsin and chymotrypsin which hydrolyze the peptide bonds between amino acids resulting in short peptide chains
* peptidases split the peptide chains into single amino acids
* amino acids are absorbed via active transport into the villi of the small intestine
* the blood stream carries the amino acids to the liver

Absorption of Lipids in the SI

fat → bile → emulsification into triglyceride → enzymes → glycerol & fatty acids → diffusion → triglycerides → protein-coated triglycerides → lymph vessel

\[using lipase enzymes\]

* fats arrive in the small intestine which triggers bile to emulsify them into a fine suspension
* emulsification is a physical process bc the bonds that join glycerol & fatty acids are not hydrolyzed
* lipase breaks down fats into glycerol and fatty acids and absorbed by the villi by diffusion
* triglycerides are reassembled and coated w/ proteins to make them soluble by entering lymph vessels
* lymph vessels: drain near the heart into the blood stream to be distributed to body cells

Regulation of the Digestive System

* coordinated by nervous system (sight + smell) and endocrine system (hormones)
* when food enters your stomach, it secrete gastrin, stomach releases gastric juices and start muscle contractions
* when stomach pH decreases you stop releasing gastrin (negative feedback loop)
* when the chyme enters the small intestines, duodenum releases secretin, CCK, and GIP; act on the stomach to stop contractions
* CCK: stimulate pancreatic secretions & gall bladder
* secretin: will stimulate bicarbonate ions from the pancreas