D1 A. Digestive System Flashcards
Nutrient
A substance that provides nourishment essential for growth and the maintenance of life
Essential Nutrients
- Carbohydrates (sugar)
- Lipids (fats)
- Proteins
- Vitamins
- Minerals
- Nucleic Acids
Water is not a nutrient even though its essential for life
True or False
Starch is a type of carbohydrate
True
True or False
When fats are digested, amino acids are formed
False
True or False
Enzymes speed up the rate of digestion
True
True or False
The large intestine is longer than the small intestine
False
True or False
Proteins are made up of amino acids
True
True or False
Proteins are our main source of energy
False
Dehydration Synthesis Reaction
- The creation of larger molecules from smaller monomers
- Water is released
- Also known as condensation reaction
Hydrolysis Reaction
- A chemical reaction where water molecules break larger molecules (polymers) into smaller ones (monomers)
Metabolism
The totality of chemical reaction that occur in a cell/organism
- Provide energy
- Enable synthesis to make new materials
Anabolism
Anabolic reactions build up complex molecules from simple ones
- Formation of macromolecules from monomers
- Condensation reactions
Catabolism
- Breaks complex molecules into simpler ones
- Releases monomers
- Hydrolysis reactions
Organic Compounds
- Carbon-containing molecules
Exceptions: Carbonate and oxides of carbon such as carbon dixoide
Carbohydrates
- Fast energy nutrient
- Largest component in most diets
- Get these from plants → cannot produce them ourselves
Carbohydrate Structure
- Single sugar (monomers) or chain of many sugar units (polymers)
- Classified by the number of sugars they contain
- Chemical Formula: Usually at a ratio of 1C: 2H : 1O
- “ose” suffix
Monosaccharides
- Simple sugar (single sugar units); one sugar ring
- 3-6 carbons
* Glucose
* Fructose
* Galactose
Isomers
- Same chemical formula, but different arrangements of atoms
Disaccharides
- 2 sugar rings / monosaccharides together
- Formed via dehydration synthesis
- Water molecule is formed from 2 monosaccharides
- Glycosidic bond is formed
- Break disaccharide bond via hydrolysis (opposite)
- Water molecule is used to break bond
- Maltose: 2 sugar units
- Sucrose: 1 glucose + 1 fructose
- Lactose: 1 glucose + 1 galactose
Polysaccharides
- Carbohydrates fromed from many monosaccharide subunits
Polysaccharides
Cellulose
- Cellulose: Polysaccharide that makes up plant cell walls (glucose)
- Different bonding that starch and glycogen
- Composed of B-glucose subunits (linear arrangement)
Polysaccharides
Glycogen
- Glycogen: polysaccharides used in animals to store carbs (glucose)
- Energy storage in humans and animals
- Composed of a-glucose subunits (branched orientation)
Polysaccharides
Starch
- Starch: Energy storage used in plabnts. Exists in form of amylose or amylopectin
- Amylose: 1000 or more glucose subunits; unbranched polymer of glucose
- Composed of a-glucose subunits (linear)
- Amylopectin: 1000-6000 glucose subunits
- Composed of a-glucose subunits (branched)
Lipid Function
- Storage of energy (triglycerides)
- Hormonal roles (e.g. steroid hormone)
- Insulation (e.g. sphingolipids)
- Protection of internal cavities (e.g. fats and waxes)
- Structral components of cells (e.g. phospholipids)
Lipid Structure
- Non-polar
- Composed of 2 structural units; glycerol and fatty acids
- Combined via dehydration synthesis to form an ester bond
Triglycerides
- Long-term energy source
- Glycerol + 3 fatty acids
- Removal of water during synthesis
- Oils: Triglycerides that are liquid at room temp
- Unsaturated fat: Some double bonds between carbon atoms
- 1 double bond → monounsaturated
- 2 or more double bonds → polyunsaturated
- Reactive; more easily broken down
Fatty Acids
Fats - Usually solid at room temperature
Saturated Fatty Acid - Only single bond between carbon atoms
- Strong bonds; hard to break down
- COOH is a carboxylic acid
- It’s linear shape (14-20 carbons) makes the structure of a fatty acid an acid
- Single bonds between carbons, double bonds between carbon and oxygen
Structural Isomers
Cis Isomer
- H atoms are on same side
- Double bond creates kink
- Are loosely packed (liquid)
- Occurs commonly in nature
- Generally good for health
Structural Isomers
Trans Isomer
- H atoms on different sides
- No kink in chain is created
- Are tightly packed (solid)
- Common in processed food
- Generally bad for health
Phospholipids
- Phosphate group bonded to glycerol and 2 fatty acids
- Negatively charged P replaces one of the fatty acids
- Head (phosphate + glycerol): Polar end = soluble in water
- Tail (fatty acids): Non-polar = insoluble in water
Waxes
- Long-chain fatty acids joined to long-chain alcohols or to carbon rings
- Insoluble in water
- Waterproof coating on plant leaves, animal feather, fur
Energy Storage - Lipids vs. Carbohydrates
Storage
- Carbohydrate - Short term
- Lipid - Long term
Osmotic effect
- Carbohydrate - More effect on cell
- Lipid - Less effect on cell
Digestion
- Carbohydrate - Readily digested
- Lipid - Less easily digested
ATP yield
- Carbohydrate - Lower (rougly half)
- Lipid - Higher (roughly x2)
Solubility
- Carbohydrate - Water soluble (monomers)
- Lipids - Not water soluble
Body Mass Index
BMI = Mass in kg / (height in m)2
- Value between 18.5 - 24.9 is healthy
Protein Functions
- Defense (antibodies)
- Movement
- Catalyst (enzyme)
- Signalling (hormone)
- Structure (mechanical support)
- Transport (carrier/channel proteins, hemoglobin)
What are proteins made out of
- Amino acids
- Carbon
- Oxygen
- Hydrogen
- Nitrogen
- Sulfur
How many differen amino acids are there
20:
9 ESSENTIAL, 11 NON-ESSENTIAL
What determines type of protein
Order and # of proteins
Polypeptide
Chain of amino acids
Protein levels of structure
Primary
- Unique sequence of amino acids in the chain
- Determines secondary structure
Protein levels of structure
Secondary
- Formed by hydrogen bonds between peptide chains (between backbone, not R group)
- H bond can pull chain into alpha helix and beta pleated sheets
Types of interactions
Hydrophobic interactions
These amino acids orient themselves towards the center of polypeptide to avoid the water
Types of interactions
Disulphide Bridge
The amino acid cysteine forms a bond with another cysetine through its R group
Types of interaction
Hydrogen Bonds
Polar “R” groups on the amino acids form bonds with other Polar R group
Types of interactions
Hydrophillic Interactions
These amino acids orient themselves outwards to be close to the water
Types of interactions
Ionic Bonds
Positively charged R groups bond together
Types of interactions
Van der Waals
- Weak interactions between hydrophobic side chains
- Increases stability
- Responsible for folding
Types of interactions
Covalent Bonds
- Disulfide bonds
- Form disulfide bridge - Strong links
Protein levels of structure
Teriary
- Depends on 1o and 2o structures
- Additional bending/folding due to interactions between R groups of amino acids
Fibrous Protein
- Has a structural role
- Insoluble in water
Globular Protein
- Has a functional role
- Soluble in water
Protein levels of structure
Quaternary
- Large, globular proteins
- 2 or more polypeptide chains (same or different)
2: dimer
4: tetramer - Some polypeptides do not have a quaternary structure
Why do proteins fold
To be more stable
Denaturation
Uncoil, assume new shape = change in biological property
- When the influencing factor is removed, the protein will assume its original shape
2 key coniditons that can denature proteins
- Temperature - Can disrupt bonds that hold proteins together
- pH - Can alter charge of protein, and change its solubility/shape
Coagulation
Permanent change
- E.g. Boiling an egg = Change in protein shape
Genome
All the genes of a cell, tissue, or an organism
Proteome
All the proteins produced by a cell, tissue or organism
- Individuals have a unique proteome
- Variable because only some cells produce specific proteins
- Human proteome = 100 000 proteins
- Small differences in DNA = differences in proteome
Cholestrol
- Type of lipid found in cell membranes
- Used to synthesize hormones
- Lipoprotein = protein + lipid
- HDL = High Density Lipoprotein (good) (bring LDL to liver to be broken down)
Nucleic Acid
- Hereditary material
- Composed of nucleotides
Enzymes
- Most reactions are not spontaneous
- Add thermal energy to system = increase kinetic energy = faster, more collision = more likely for reaction to occur
- Enzymes work at low temp.
- 3D proteins that act as catalysts
- Increase reaction probability
- Often end with -ase
Catalysts
- A substance that increases the rate of chemical reaction without being changed itself or become part of the product
- Each enzyme usually controls just one reaction
Activation Energy
- The energy that must be supplied to cause a reaction
- Enzymes lower the necessary energy of activation
4 Steps of Enzyme Action
- Subrate binds with enzyme
- Enzyme undergoes confirmational change
- Substrates converted to products
- Products are relased
Lock & Key Model
- Enzymes act as keys to lock or unlock substrates
- Substrate: Reactants in an enzymatic reaction
- Active Site: Region on enzyme where substrates attach
Induced Fit Model
- Replaced lock and key model
- The enzyme (active site) changes shape to fit between site and substrate
- Increases rate of chemical reaction
Particle Collision Theory
- The frequency of collisions determines the rate of enzyme activity
- If you increase the probability of collisions occuring, then you increase the frequency of enzyme activity
Factors helping ezyme combine with substrate
Coenzymes
Molecule that assists an enzyme to complete a reaction (organic), synthesized from vitamins
Factors helping enzyme combine with substrate
Cofactors
Inorganic enzyme helpers
Factors affecting enzyme activity
Temperature
- Increase temp. → increase activity, to a point
- Too low of temp. → not enough energy for reaction to occur
- Enzyme is denatured at high temps.
Factors affecting enzyme activity
pH
- Changing pH changes charge/solubility or shape of enzyme
- Decreases ability to bind to the substrate
- Optimal pH = peak enzyme activity and enzyme specificity
Factors affecting enzyme activity
Substrate Concentration
- The greater the number of substrate molecules = the greater the chance of successful collisions
- Plateau because all active sites are occupied
Factors affecting enzyme activity
End Product Concentration
- As enzymes work, they produce an end product
- Some are able to affect another enzymes activity and thus cause feedback inhibition
- Some are poisonous to enzymes in high concentrations
- The substrate can bind to the active site
- Final product attaches to the regulatory site and changes the shape of the enzyme so the substrate cannot bind
Factors affecting enzyme activity
Competitive Inhibitors
- Molecule so close to enzyme’s substrate that it competes for the active site
- Inhibitor binds to enzyme and will not allow product to be produced
Factors affecting enzyme activity
Non-competitive inhibitors - allosteric activity
- A chemical binds to a regulatory site causing the active site to change shape
- Enzyme that shapes due to a chemical binding to the regulatory site = allosteric activity
- Sometimes this can cause feedback inhibition (shut off activity)
- Sometimes this can cause a reaction to proceed (precursor activity)
Regulatory of Enzyme Activity - Allosteric Activity
Negative Feedback / Feedback Inhibition
- Occurs when an end product can bind to an enzyme and become a noncompetitive inhibitor slowing the rate of reaction of an enzyme
Regulatory of Enzyme Activity - Allosteric Activity
Precursor Activity
- Substrate molecules accumulate → substrate molecules attach to the regulatory site of an enzyme in a pathway → improves fit between enzyme and substrate → increases reaction rate
Digestion
- Process where food is broken down into nutrients your body can use as energy
- Beings in your mouth, finishes at the terminal ileum
Mechanical Digestion
Cutting/crushing of food into smaller pieces
Chemical Digestion
Breakdown of food using enzymes
Peristalsis
Rhythmic muscle contraction of longitudinal muscles
- Occurs in: Esophagus, Stomach, Intestines, Rectum
Segmentation
Rhythmic muscle contractions of circular muscles. Moves food back and forth (mixes food)
4 Main components of digestive process
- Ingestion (taking in nutrients)
- Digestion (breakdown of complex organic molecules → smaller components by enzymes)
- Absorption (transport of digested nutrients to body cells)
- Egestion (Removal of food waste from body)
Roles of saliava
- Contains amylase to breakdown starch
- Lubricates mouth/throat
- Protects teeth from cavity causing bacteria
Oral Cavity
- Salivary glands secrete saliava (begins chemical digestion)
- Tongue determines which food needs to be further processed
- Taste buds communicate which food needs to be processed further
- Moves food and helps shape it into a bolus
- When swallowing - pushes bolus to back of oral cavity and pharynx
Esophagus
- Flexible tube that leads to stomach
- Secretes mucus
- Passes through the diaphragm to connect with stomach at the lower esophageal sphincter which regulated entry
Stomach
- At the left side of the abdodmen
- Secretes gastric juices
- Stores food, continues digestion but does absorb a few compounds
- Has a lining of a layer of mucus which protects it from being digested by pepsin
Pyloric Sphincter
Moves food and stomach acid → small intestine
Chyme
Ingested food and digestive juice
Stomach - Mechanical Digestion
Crisscrossed muscle layers that create chruning and mixing motions
Gastrin
A hormone that stimulates release of HCL
HCL
- Secreted from parietal cell
- Can convert pepsinogen → pepsin
Pepsin
Begings to hydrolyze protein into smaller polypeptides by breaking peptide bonds; works in acidic conditions
Stomach - Peptic Ulcer
- Ulcers are open sores that form in stomach/duodenum
- When the mucus layer is reduced, stomach acid can damage the tissue
Small Intestine
Responsible for:
- Breaking down food
- Absorbing nutrients
- Solidifying waste
3 Sections:
- Duodenum
- Jejenum
- Ileum
Small Intestine
Duodenum
- Chyme leaves the stomach and enters the duodenum
- Low pH of chyme stimulates hormone secretion
- Secretin causes release of NaHCo3 (sodium bicarbonate) from the pancreas
- NAHCo3 nuetralizes gastric fluid → raising pH to 8
- Amino acids and fatty acids in chyme releases CCK
- CCK stimulates pancreas to release pancreatic enzymes
- CCL stimulates gallbladder to contract and release bile
Duodenum response to lipids
- Secretes enterogastrone hormone
- Inhibits secretion of gastric juices by stomach
- Slows down peristalsis; causing food to move slowly
- Thus, increased time for fat digestion
Accessory Organs
Food does not pass directly through these organs, but they still contribute to digestion
- Salivary glands
- Pancreas
- Liver
- Gallbladder
Pancreas
Endocrine Cells (produces hormones)
- Insulin (decrease blood glucose)
- Glucagon (increase blood glucose)
Exocrine Cells (produce gastric juice) - main digestive enzymes
- Pancreatic amylase
- Proteases
- Pancreatic lipase
Liver Functions
- Makes bile
- Cleans toxins out of blood
- Removes old blood cells
- Stores glycogen/vitamins
- Converts glycogen (starch) to sugar
- Breaks down fatty acids
Bile
- Stored in gallbladder
- Not an enzyme; it is an emulsifier
- Involved in physical digestion
- Contains bile salts which aid in fat digestion
- When fats are in stomach, signal hormone CCK → blood → gallbladder → trigger gallbladder to release bile salts
Small intestine secretions
- Lining of duodenum can also secrete digestive enzymes
- Peristalsis moves mixture of chyme and digestive juices through intestine
- Most digestion complted in duodenum
At the end of digestion
- Carbohydrates hydrolyzed to monosaccharides
- Proteins break down into individual amino acids
- Fats hydrolyzed by lipase into glycerol and fatty acids
Small intestine secretions
- DNA will also be digested in the enzymes via nucleases
- Will result in nucleotides that cells use to replicate their own DNA
Absorption in the small intestine
- Jejenum and ileum main absorption of nutrients and water into circulatory and lymphatic system
- Large folds in lining have fingerlike projections called villi
- Each villi has microvilli
- Increases absorption even more
How do the circulatory, lymphatic, and digestive system interact
Each villus has a small lymph vessel and a network of capillaries
Lacteal
Absorbs fatty acids and glycerol
Capillary
Absorbs nucleotides, amino acids, monosaccharides
Epithelial cells are connected by ____ ____
Tight junctions
- Creates impermeable barrier between the body tissues and digestive juices in the lumen
Villi Functions
MR SLIM
- Microvilli (increases SA:V)
- Rich capillary network (transports digested products)
- Single-layer epithelium (minimises diffusion distance)
- Lacteals (absorbs lipids into the lymphatic system)
- Intestinal glands (exocrine pits release enzymes)
- Membrane proteins (facilitates transport of products)
Methods of membrane transport
- Co-transport (active)
For: Glucose, Amino Acids - Facilitated Diffusion
For: Monosaccharides - Osmosis
For: Water - Simple Diffusion
For: Triglycerides
Protein Digestion/Absorption
Secondary Active Transport
Glucose and amino acids are co-transported with sodium ions
Protein Digestion/Absorption
Facilitated Diffusion
Monosaccharides, vitamins and minerals are transported by channel proteins
Protein Digestion/Absorption
Simple Diffusions
Hydrophobic and lipophilic substances (fats) may freely cross the membrane
Protein Digestion/Absorption
Bulk Transport
- Vesicles form around fluid containing dissolved materials
- Pinocytosis takes less time than shuttling materials via membrane proteins
Lipid Digestion/Absorption
Lipids are insoluble in water and need to be complexed with proteins in order ot be transported in the blood
- Lipid globules are emulsified by bile salts before being chemically digested by pancreatic lipases
- Components are combined with protein to form chylomicrons which are transported to the liver
- Liver converts chylomicrons into soluble lipoproteins
Carbohydrate Digestion/Absorption
- Starch is main polysaccharide in human diets
- Starch is digested via amylase into smaller subunits
- Glucose monomers are used for cell respiration or processed and stored in the liver as glycogen via glycogenesis (liver)
Protein Digestion/Absorption
Protease
- Proteases are secreted in an inactive form so they don’t synthesize the cells that digest them
- Activated by specific enzymes or chemical agents (low pH)
Large Intestine Function
- Absorb water (mineral and salts)
- Decompose leftover organic material with help of bacteria
- Produce vitamin K and B and folic acid required for red blood cell production
- Stores, eliminates solid waste
Large Intestine
Bowel Movement
- Buildup signal CNS which promts movement
- Stinky because of bacteria
- Removes toxic wastes from body
- Not enough cellulose (fibre) = less movement
Large Intestine
- At the end of the small intestine, undigested material pass through the ileocecal sphincter into larger intestine
- Large intestine is wide and short
Three sections:
- Ascending
- Transverse
- Descending
