UD1: Digestive System

homeostasis

The process by which the body maintains a stable internal environment despite changes in external conditions, crucial for proper functioning of the digestive system.

Our body maintains homeostasis through a 3 part mechanism

Sensor: detects change in the external environment

Effector: brings internal temp back to normal

Control Centre: activates effector based on info from sensor

6 essential nutrients

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

• Vitamins

• Minerals

Carbohydrates subunits

composed of monosaccharide subunits (monomers)

Lipids subunits

composed of Glycerol & Fatty Acid subunits

Proteins subunits

composed of amino acid subunits

Nucleic Acids subunits

composed of Nucleotide subunits

Assembling Macromolecules

Dehydration synthesis - removal of a water molecule (Needs enzymes)

Disassembling of Macromolecules

Hydrolysis - addition of a water molecule (Needs enzymes)

Carbohydrates

• (C + H + O)

• Main source of Energy

Monosaccharides

• Glucose

• Fructose

• Galactose

Disaccharides

• Maltose = Glucose + Glucose

• Sucrose = Glucose + Fructose

• Lactose = Glucose + Galactose

Polysaccharides

• Cellulose - forms structural material of plants

• Starch - storage form of carbs in plants

• Glycogen - storage form of carbs in animals

Lipids

• (C+H+O)

• Long term energy storage, forming cell membrane, protection of internal organs, insulation, and formation of hormones

• NON POLAR & insoluble in water

• Composed of glycerol molecule bonded to fatty acids (ex. monoglycerides = 1 fatty acid)

Saturated Fatty Acids

• contain only single bonds between carbon atoms

• usually from animal sources and solid at room temp

Unsaturated Fatty Acids

• have 1 or more double bonds between carbon atoms

• usually from plant sources and are liquid at room temp

Proteins

• (C+H+O+N)

• Transport, Blood clotting, immunity, enzymes, for chemical reactions, structure and support

• Composed of chains of amino acids joined by peptide bonds

Amino acids

• (C-H) + (Amino Group with Nitrogen) + (Acid group) + (R group 20 types)

• body can synthesize 11 amino acids the other 9 are called essential amino acids that come from food

Peptide

chain of several amino acids bonded together

Polypeptide

chain of peptides

Nucleic Acids

• (C+H+O+N+P)

• makes chemical code for DNA & RNA

DNA

deoxyribonucleic acid: codes for production of proteins

RNA

ribonucleic acid: helps in the assembly process of proteins

Nucleotides

• (5 Carbon sugar) + (Nitrogen base) + (Phosphate group)

• adenine

• guanine

• cytosine

• thymine

• create base pairs for DNA

• (c&g) (a&t)

Enzymes

• protein molecule that acts as a catalyst to speed up chemical reactions

• can be used over and over again

• enzymes have a specific shape of which substrate it can bind to

4 factors that affect enzymes

• Temp

• pH

• competitive inhibitors (molecules that attach to active site preventing substrate from binding)

• non competitive inhibitors (molecules that bind to a regulatory site changing the shape of enzyme preventing substrate from binding to active site)

• Factors that can DENATURE (loosing shape and function) the enzyme

Digestive system

Mechanical Digestion

• breaking down food into smaller pieces to increase surface area

• ex. chewing, churning in stomach, segmentation in small intestine

Chemical deigestion

• Enzymes are used to aid chemical breakdown of macromolecules to smallest subunits

Mouth

• Mechanical Digestion: chewing food

• Chemical Digestion: (CARBS only)

  • salivary amylase enzymes from salivary glands (pH-7)

  • breaks down complex carbs into polysaccharides

Esophagus

• passage way from mouth to stomach

• epiglottis covers trachea to prevent food and liquid from entering lungs

• uvala prevents food entering nasal passages

peristalsis

a wave like series of muscular contractions that moves the bolus

esophageal sphincter

controls entry to stomach

Stomach

• storage

• pH of 2

• mechanical digestion: churning

• chemical digestion: Proteins

  • Gastric juices that contain pepsinogen and HCL combine with food to create chyme

  • pepsin (pepsinogen in active form) breaks down proteins into polypeptides

• Ends with pyloric sphincter

Small Intestine

• inner surface covered with villi which contains thousands of microvilli that increase surface area

• Duodenum: ducts from the gall bladder and pancreas join to

• Jejunum: food is broken down and some absorption of nutrients

• Ileum: absorption of nutrients and pushes chyme into large intestine

Pancreas

• secretes bicarbonate ions neutralizes HCL making pH of small intestine 8

• Secretes enzymes

  • Carbohydrases: pancreatic amylase

  • Proteases: trypsin, chymotrypsin

  • Lipases

  • Nucleases

Liver

• produces bile salts that emulsify fats that break lipids into tiny droplets (mechanical digestion)

• Stores excess glucose in the form of glycogen

Gallbladder

Stores bile

Large intestine

• pass through the ileocecal sphincter

• water and salts are absorbed in the colon then feces is releaesd out da anuss hahahahah