Are you what you eat? Flashcards
What is an Enzyme?
- A protein catalyst that increases the rate at which a chemical reaction proceeds, without the enzyme being permanently changed.
- Highly specific – Active site on an enzyme can only bind to specific reactant.
- Many different enzymes needed in the body for different chemical reactions.
What does lipase, protease, amylase breakdown?
- Lipase- enzyme that breaks down lipids
- Protease- breaks down proteins
- Amylase- breaks down carbohydrates
What is Enzyme Action?
The enzyme brings the two reacting molecules together. After the reaction, the unaltered enzyme can be used again.
What is the Digestive Tract called?
Digestive tract: also called alimentary tract.
What are Accessory Organs?
Accessory organs: Primarily glands, secrete fluids into tract.
What are the organs of the Digestive System?
- Oral cavity (mouth) with salivary glands.
- Pharynx (throat).
- Oesophagus
- Stomach
- Small Intestines (duodenum, ileum, jejunum) with liver, gall bladder & pancreas as accessory organs.
- Large Intestine including cecum, colon, rectum & anal canal.
- Anus
What are the functions of the Digestive System?
- Ingestion: Introduction of food into stomach (via mouth).
- Mastication: Chewing. Chemical digestion requires large surface area so breaking down large particles mechanically facilitates chemical digestion.
- Secretion: Lubricate, liquefy, digest (e.g. Mucus: secreted along entire digestive tract, lubricates food, coats and protects lining).
- Digestion: Mechanical and chemical digestion of food into nutrients.
- Absorption: Movement of nutrients out of digestive tract into cells.
- Elimination: Waste products removed from body; faeces. Defecation.
What is the Histology of the Digestive System?
- Mucosa: innermost layer, secrets mucus.
- Submucosa: connective tissue layer, contains blood vessels, nerves etc.
- Muscularis: 2/3 muscle layers, movement & secretion.
- Serosa / Adventitia: outermost layer, connective tissue, stability.
What is Peritoneum?
The walls & organs of the abdominal cavity are lined with serous membranes.
What is the Visceral Peritoneum & Parietal Peritoneum?
- Visceral Peritoneum-Covers organs.
- Parietal Peritoneum-Covers interior surface of body wall.
What is Mesenteries?
Mesenteries-Peritoneum (epithelial tissue) which connects organs together. Routes by which vessels & nerves pass from body wall to organs.
What is Greater & Lesser Omentum?
- Greater Omentum-Connects stomach to transverse colon.
- Lesser Omentum-Connects stomach to liver & diaphragm.
What does the Oral Cavity do in Digestion?
- Digestion begins in the oral cavity (mouth).
- Hard Palate: Hard bone, anterior.
- Soft palate: Soft muscle, posterior.
- Tongue
- Teeth
- Masticate (chew) food and turn it into a bolus.
What are the sets & types of teeth?
-Two sets:
Primary, Milk- Childhood
Permanent or Secondary- Adult (32)
-Types: Incisors, canines, premolars, molars
What do the Salivary Glands do in Digestion?
- Salivary glands (green) – produce & secret saliva into the oral cavity.
- Saliva – protects oral cavity, moistens, lubricates and digests food.
- Amylase – enzyme found in saliva that breaks down carbohydrates into smaller sugars.
- Lysozyme – antibacterial enzyme
What doe the Pharynx connect to and what does Uvula do?
-Pharynx (throat) – connects oral cavity to the oesophagus.
oUvula (soft palate) prevents food/drink from entering the nasopharynx.
What is the Oesophagus and what does the Epiglottis do?
-Oesophagus – tube that connects pharynx to stomach. 25cm long, lies posteriorly to the trachea.
oEpiglottis prevents food/drink from entering the trachea.
What are the phases of Swallowing?
- Voluntary phase: Tongue pushes bolus to back of oral cavity towards pharynx (oropharynx).
- Pharyngeal phase: Soft palate (Uvula) close off the nasopharynx. Bolus touches receptors on oropharynx and swallowing reflex moves bolus down pharynx and into oesophagus. Epiglottis covers trachea.
- Oesophageal phase: bolus is moved down oesophagus towards stomach by peristalsis.
What is Peristalsis and the process?
- Process by which food moves through the gut. Waves of smooth muscle relaxations & contractions.
1. A wave of smooth muscle relaxation moves ahead of the bolus, allowing the digestive tract to expand.
2. A wave of contraction of the smooth muscle behind the bolus propels it through the digestive tract.
What does the Stomach do in Digestion?
- Located in abdomen. ‘holding point’ for food.
- Food comes from the oesophagus and the stomach mixes it (churns) into chyme (thick liquid).
- Produces mucus, hydrochloric acid, protein digesting enzymes (pepsin).
- Contains a thick mucus layer that lubricates and protects epithelial cells on stomach wall from acid pH 2-3.
What are the openings in the stomach?
- Gastroesophageal (cardiac): to oesophagus
- Pyloric: to duodenum
What are the parts of the stomach?
- Cardiac
- Fundus
- Body
- Pyloric: antrum and canal
What are the layers of the stomach?
-Visceral peritoneum or serosa
-Muscularis: three layers
o Outer longitudinal
o Middle circular
o Inner oblique
-Submucosa
-Mucosa
-Rugae: folds in stomach wall that allow stomach to stretch after eating
What are the movements if the stomach?
- 3 muscular layers enable churning of food. Make Chyme.
- Combination of mixing waves (80%) and peristaltic waves (20%)
- Both oesophageal and pyloric sphincters are closed.
- Stomach empties every 4hrs (6-8 after a fatty meal)
What does the Small Intestine do in Digestion?
- Very long ~6m, small diameter.
- Large surface area for efficient absorption of nutrients.
What are the divisions of the small intestine?
oDuodenum- first 25 cm beyond the pyloric sphincter.
oJejunum- 2.5 m.
oIleum- 3.5 m.
What do the folds do in the small intestine and what helps this occur?
- ‘Folds’ increase surface area of small intestine 600-fold. Increase absorption.
1. Plicae circulares: Circular folds in the wall of the small intestine
2. Villi: Folds of the mucosa that contain capillaries and lacteals.
3. Microvilli: Small folds on epithelial cell surface.
What does the Duodenum do in the Small Intestine?
- Chyme mixes with various digestive enzymes.
- Liver / gall bladder: Bile enters via the common bile duct, emulsifies fats.
- Pancreas: enzymes enter via the pancreatic duct.
What does the Liver do in Digestion?
Makes bile ~100ml/day. Stores glucose (as glycogen) and lipids for energy. Detoxification.
What does the Gallbladder do in Digestion?
Stores concentrated bile.
What does the Pancreas do in Digestion?
Produces digestive enzymes. Produces insulin and glucagon for blood sugar homeostasis.
What does the Large Intestine do in Digestion?
- Absorption of water.
- Extends from ileocecal junction to anus.
- Consists of cecum, colon (ascending, transverse, descending, sigmoid), rectum, anal canal.
- Bacteria / microbes synthesise vitamin B & K.
o18-24hr transit time; chyme -> faeces.
o1500 mL chyme enter the cecum, 90% reabsorbed yielding 80-150 mL of faeces.
oDefecation reflex
Where does Digestion occur in the body?
-Digestion – mouth, stomach, small intestine.
Breakdown of food molecules for absorption into circulation.
oMechanical: breaks large food particles too small.
oChemical: breaking of covalent bonds by digestive enzymes.
What does Absorption do in the body?
-Absorption – nutrients from the small intestine, water from the large intestine.
oMolecules are moved out of digestive tract and into circulation for distribution throughout body.
Why are chemicals take into the body?
- Produce energy.
- Provide building blocks to build other molecules.
What are the classes of nutrients?
carbohydrates, proteins, lipids, vitamins, minerals, water
What are the major organic nutrients?
- Carbohydrates, proteins & lipids are major organic nutrients (organic =contains carbon).
- Need large amounts of carbs, proteins, lipids & water
- Only need small amounts of vitamins & minerals
- Taken into body without being digested
What are essential nutrients?
Essential nutrients – are chemicals that must be taken into the body, because we can’t make them ourselves.
-Include some amino acids/fatty acids/carbs, water, most vitamins & minerals
Give examples of the nutrient. classes.
- Carbohydrates – mono / di / polysaccharides - plants, vegetables
- Lipids – triglycerides - oils, dairy, animal fat, eggs
- Proteins – chains of amino acids - meat, fish, poultry
- Vitamins – organic molecules (vit A,B,E) – animal and plants products
- Minerals – inorganic nutrients (calcium, iron) – animal and plant products
- Water
What are the recommended amounts for carbs, proteins & lipids?
-Carbohydrates
o 45-65% of daily intake of kilocalories
-Lipids
o 20-35% or less of total daily kilocalories
-Proteins
o 10-35% of total kilocalories per day
-60% 30% 10% (Carbohydrates>Lipids>Proteins)
-Consider personal needs & source.
What are Carbohydrates as a Nutrient in the body?
-Most come from plants (exception lactose from milk)
-Contain carbon (C), hydrogen (H) and oxygen (O) = CHO.
-2H and 1O for every C (the 2H: 1O ratio is same as for water).
Carbo = carbon; hydrate = water/hydrated
-Large molecules are made up of small building blocks
oMonosaccharides (mono = 1, saccharide = sugar)
Examples of Monosaccharides
o Glucose (blood sugar) o Fructose (fruit sugar) o Galactose (milk sugar)
Examples of Disaccharides
- Sucrose (table sugar) = glucose + fructose
- Lactose (milk) = glucose + galactose
- Maltose = glucose + glucose
Examples of Polysaccharides
-Long chains - 3000+ monosaccharides
-Glycogen
oAnimal polysaccharide
oGlucose molecules
oStored in humans in liver & muscle
-Starch & cellulose
oPlant polysaccharides
oHumans break down starch
-energy
oHuman can’t break down cellulose
-dietary fibre
How are Carbohydrates absorbed in the body?
- Polysaccharide chain e.g. glycogen. Digested by saliva in oral cavity & pancreatic amylase in duodenum.
-Disaccharide chain e.g. sucrose. Digested by sucrase in the intestine.
Monosaccharide chain e.g. glucose. Glucose absorbed into blood via villi / microvilli in intestine. Transported to liver via hepatic portal vein.
How are Carbohydrates used in the body?
- Glucose= produce ATP
- Excess glucose= glycogen and stored in muscles and liver cells.
- Excess beyond storage is converted to fat.
- Sugars also become part of DNA, RNA, and ATP, glycoproteins, glycolipids.
What do Proteins contain?
Contain carbon (C), hydrogen (H) and oxygen (O), nitrogen (N), sometimes sulphur S(S).
What are Amino Acids?
- Amino acids are the basic building blocks
- Each amino acid has an amine group (NH2), a carboxyl group (COOH), a hydrogen and a side group.
- Side group is what is different between amino acids.
- Amino acids link together to form peptides and proteins.
- Amino acids are not stored in the body.
What are Essential & Non-Essential Amino Acids?
- Essential amino acids, can’t be produced by body so must be obtained from the diet, e.g. histidine, isoleucine (9 in total).
- Non-essential amino acids are still required by our body, but these we can synthesize from essential amino acids.
What is the function of Proteins?
-Regulate body functions. oGlobular proteins – haemoglobin oStructural - muscle proteins or CT oCell membrane transport oEnzymes oHormones oAntibodies
What are Complete & Incomplete Proteins + examples?
-Complete protein – food that contains enough of all 9 essential amino acids.
oMeat, fish, poultry, milk, cheese eggs
-Incomplete protein
oLeafy green vegetables, grains, legumes –have to mix these to get all the amino acids.
How are Proteins Absorbed in the body?
- Protein (long chain of amino acids) digested by pepsin in stomach.
- Polypeptides digested by trypsin in duodenum.
- Peptides and individual amino acids are absorbed into the blood via villi / microvilli in intestine.
What are Lipids composed of?
- Protein (long chain of amino acids) Digested by pepsin in stomach.
- Polypeptides digested by trypsin in duodenum.
- Peptides and individual amino acids are absorbed into the blood via villi / microvilli in intestine.
What are Triglycerides?
-Glycerol + 3 fatty acids
-Fatty acids
oDifferent lengths (e.g. 14 or 18 C atoms.
What are Saturation, Saturated, Unsaturated, Trans Fats?
Saturation – how many H atoms on each chain.
Saturated– animal fats, e.g. beef, pork, milk, cheese, butter.
Unsaturated – contains one or more double bonds in the carbon chain, so there is less H atoms, more relaxed structure (liquid at RT).
Trans fats – unsaturated fats that are artificially altered to be more saturated (CVS risk).
How are Lipids absorbed?
- Lipid (triglycerides) digestion begins in the duodenum.
- Bile from the gall bladder emulsifies lipids.
- Lipase from the pancreas causes further breakdown
- Short chain fatty acids (monoglycerides) are absorbed into the lymphatic system via lacteals.
- Lipids are stored in the adipose tissue and liver until needed.
How are Lipids used in the body?
- Triglycerides: used to produce ATP (excess stored in adipose or liver).
- Cholesterol: found in liver & egg yolks or manufactured by body. Component of plasma membranes modified to form bile salts.
- Phospholipids: major components of plasma membranes, myelin sheath, part of bile.
- Eicosanoids: derived from fatty acids. Involved in inflammation, blood clotting, tissue repair, smooth muscle contraction.
How is Water Absorbed in the body?
- Approximately 9L of water enters the digestive tract each day.
- 99% of water entering the intestine is absorbed.
- Water can move across the intestinal wall in either direction if required.
- Ions: sodium, potassium, calcium, magnesium, phosphate are actively transported.
What are Vitamins?
- Organic molecules in very small quantities in food.
- Essential for normal metabolism and can’t be produced by the body.
- No one food provides all necessary vitamins
- Some vitamins produced by intestinal bacterial e.g. vitamin K
- Vitamins can be fat soluble (A, D, E, K) or water soluble (B and C vitamins)
What happens when the body has too much Vitamins?
- Vit C – stomach inflammation; diarrhea.
- Vit A – toxic during pregnancy
- Vit D - alter calcium metabolism
What are Vitamin Deficiencies?
- Vit D – rickets
- Vit C–scurvy
- Vit B1 (thiamine) – beriberi
What are Minerals?
-Inorganic nutrients
oMajor minerals >100 mg/day
-Calcium, magnesium, sodium, potassium • Trace minerals < 100 mg/day selenium, zinc, copper.
-Components of co-enzymes, some vitamins, haemoglobin, organic molecules.
What are the functions of Minerals?
oMembrane potential & action potentials
oAdd mechanical strength to bones & teeth
-Available from both plant and animal-based foods.
What are Mineral Deficiencies?
- Iron – anaemia
- Potassium – muscle weakness, abnormal heart function
- Iodine - goitre
