Digestion Flashcards
What are essential vs non-essential nutrients?
Essential: Nutrients that cannot be synthesized by the body and have to be included in the diet.
Non: Can be synthesized by the body, must not be ingested
6 classes of nutrients
Carbohydrates
Protein
Fat
Vitamin
Mineral
Water
What are vitamins?
+Eg
Organic molecules with complex chemical structures that are often essential
eg. Vitamin B, D etc
What are minerals? What are they important for? What if you don’t get enough of them?
Chemical elements and inorganic substances that are essential nutrients.
They are important for structures such as teeth, bones
Worsened bone mineralization
What are conditionally essential nutrients?
When technically organic compounds produced by the body are sufficient, however, due to disorders (such as cardiovascular disease), their biosynthesis is inadequate.
What is the human digestive system?
A group of organs that work together to digest and absorb nutrients. Their structure allows it to move, digest , absorb and egest food.
What is the alimentary canal?
The tube includes the mouth, esophagus, stomach, small intestine, and large intestine. The whole digestive tube.
What is the role of the mouth?
Mechanical digestion and some chemical digestion of carbohydrates
What is the esophagus?
A tube that carries food from mouth to stomach
What is the simple role of the liver?
It secretes bile
What is the main role of the large intestine?
Absorbs water from indigestible food and carries the water from the body.
Where does the most digestion and absorption of nutrients occur?
The small intestine
What is the role of the small intestine?
Absorbing nutrients and digestion
What does the pancreas do?
It makes bile and helps digest fats.
What is the duodenum?
The beginning part of the small intestine.
Where does mechanical digestion of food and some chemical digestion take place?
The stomach
What happens in the stomach?
Mechanical digestion of food and some chemical digestion.
What comes before the anus?
The rectum
What doesn’t have to be digested?
Minerals, vitamins, and water. THey can be directly absorbed
What has to be digested?
Large, insoluble polymer molecules:
Carbohydrates, lipids, proteins, nucleic acids.
What is digestion?
Breaking down food via chemical and enzymatic action in the alimentary canal.
What is absorption?
When digested food is moved from the digestive system to the bloodstream (the whole body).
This occurs in the small intestine.
What happens in the small intestine?
Digested food is absorbed into the bloodstream so that nutrients can be transported through the whole body.
What is assimilation and where does it occur?
In the small intestine, nutrients are absorbed through the cell tissues. Over time fragments of these nutrients form more complex substances.
What is egestion?
The discharge of undigested/waste material
What do digestive enzymes do? Give an example
Catalyze the hydrolysis of insoluble food molecules to soluble end products. They SPEED UP
- REDUCE ACTIVATION ENERGY
Sucrose is broken down into glucose and fructose by the enzyme sucrase
What is it called when the active site of an enzyme slightly shifts to fit the substrate?
Induced fit.
Explain the second step in enzyme function (substrate is already bound to the active site.
Amino acids bind to the substrate and distort bonds, starting the reaction.
What is the composition of an enzyme and the substrate called?
Substrate enzyme complex.
What is hydrolysis?
The splitting of molecules via the addition of water. Polymers are turned into monomers
What is the monomer of starch?
glucose
What is the monomer of lipids?
fatty acid + glycerol
What is a gland?
An organ which synthesizes a substance meant for release
What are the two types of glands?
Exo and endocrine glands
What do endocrine glands secrete? Where do they secrete into?
Hormones
into the bloodstream.
What do exocrine glands secrete? Where do they secrete into?
“other stuff”
- oil
- sweat
enzyme
INTO DUCTS
What is an acinus?
A cluster of exocrine glands
- they form hollow spheres
Multiple acini are found in
One gland
1 acinus is the fundamental unit of a gland
What is a lumen in terms of acini?
The hollow space within an acinus
What is a duct?
The tube passage for secreted material
In an acini, where are vesicles found?
Within secretory cells
What are vesicles?
Small membrane-bound sacs. They store and transport molecules for secretion
What is the function of the blood vessel along the acinus?
It provides cells with nutrients to function but also deposits waste material
What is the function of the basement membrane?
It provides support to cells.
It limits contact between cells
It acts as a filter (allows only H20 and small molecules to pass)
What does an Acinus look like? Name the structures.
What is exocytosis?
When molecules are released from cells via the fusion of the cell membrane and that of the vesicle. The cell membrane expands.
What do acini cells have a lot of
Golgi- for packaging excretory material
Mitochondria- for protein synthesis/ cell activity
Rough ER- protein synthesis
What do digestive glands secrete a lot of?
Digestive juices (mostly enzymes in water)
What is the nuclear envelope connected to?
The rough ER
Step by step explanation of the endomembrane system
1) Proteins and membranes made from the rough ER flow transport vesicles to the Golgi
2) The golgi pinches off transport vesicles and gives rise to lysosomes and vacuoles
3) The lysosome is available for fusion with another vesicle for digestion
4) Transport vesicle carries proteins to the plasma membrane for secretion
5) The plasma membrane expands by fusion of vesicles, proteins are secreted from cell
What does the pancreas secrete?
“pancreas juice” which is enzymes, water and bicarbonate
into the small intestine
What does the stomach secrete?
gastric juice (Pepssin, HCl, water)
What does the liver secrete?
Bile, which is then stored in the gall bladder
What does salivary gland juice consist of?
Water, salts, amylase mucus
What is mechanical digestion?
When muscle contractions break apart and mix foods, exposing the food to gastric juices better later.
Bolus becomes chyme
What is a larger food mass turned into a smaller food mass?
Bollus to chyme
What is chemical digestion?
Ezymes and HCl digest chyme
What type f muscular contractions help digest food?
Peristalsis
What does the stomach digest?
Proteins
By what is the production of pepsin stimulated?
Presence of gastrin in blood
Why is HCL favorable for the stomach?
PH of 2
Controls pathogens in digested food
helps dissolve food
kills microorganisms
What protects the stomach lining?
Mucus
Who discovered digestion in the stomach?
Beaumont
How did Beaumont discover digestion in the stomach?
Through observing an open wound after a gunshot. He extracted food every 2-3 days and introduced food to the stomach to see the effects.
What is the secretion of food controlled by?
Nervous and hormonal mechanisms
Step by step of the secretion of digestive fluids.
1) The stomach is stretching because food has entered it
Stretch receptor proteins are activated
2) Stomach sends receptor proteins to brain (medulla oblongata)
“im stretching”
3) The brain sends a nerve signal back to the stomach “you’re stretching”
4) In response to nerve signals, the endocrine glands in the heart release the hormone gastrin into the blood
5) gastrin moves through the blood into the stomach
6) When gastrin is in the stomach, the exocrine glands secrete gastric juice
What type of proteins are enzymes?
Globular proteins
What does amylase do
Polysaccharides to monosaccharides
What does nucleases do?
Nucleic acids to nucleotides
What does Lipase do?
Lipids to fatty acids
What do proteases do? Give an example
Proteins to mino acids, pepsin
They are pepsin and trypsin
What is trypsin produced in?
pancreas exocrine glands
What are trypsin and pepsin produced as?
Inactive precursors. They are chemically altered after secretion (mixing with stomach acid) to prevent self-digestion of cells which create proteases
4 layers of the stomach lining
Mucosa, Submucosa, curcular muscle cells, Longitudal muscle cells, Serosa
What are stomach ulcers?
Sores in the stomach lining which happen when digestive juices(pepsin and HCl) eat away tissue where mucus layers have been eroded via H. pylori
Which bacteria is linked to stomach ulcers and cancers?
H. Pylori
What does H. pylori secrete that breaks down mucus?
Mucinase
How are ulcers/ H. pylori related to stomach cancer?
If the right bacteria is consumed via food and infects the exposed tissue, mutations in the DNA can occur.
In what part of the small intestine does digestion occur?
duodenum
How do antibiotics stop infection from H.pylori?
“proton pump inhibitors”
They stop HCl production through inhibiting the H+ and K+ pumps.
How are stomach ulcers treated?
antibiotics
In what part of the small intestine does absorption of nutrients occur?
ileum
What muscle makes food move along the gut?
longitudal and circular muscle
Which intestine has villi?
Small intestine- illeum
What are villi
Small folds in the intestinal lining. They are part of the mucosa layer.
ONE CELL LAYER
What is the function of villi?
Increasing surface area for nutrient absorption
Features of a villi
1 cell thick of epithelial cells and close to blood
Has a capillary bed in center that absorbs glucose and amino acids
Has a lacteal that absorbs and transports fatty acids
What is part of the villi?
Microvilli on epithelial cells
What are features of epithelial cells?
They have pinocytotic vesicles(outside to inside)
Cell junctions which give them strength and makes them impermeable to small unwanted molecules
Lots of mitochondria to fuel the active transport pf molecules to the cell from the lumen of the small intestine
What is the overall lining of villi called?
The brush border which have enzymes embedded in their membranes
They dont “flush away” after a mean
What is used to break down clumps of lipids(fats)
Bile
They are needed because lipase cannot break down the clumps
Explain the breakdown of fats via bile
Bile surrounds clumps of fats and breaks them down into smaller chunks, increasing the surface area of lipase action
What is absorption and give the 3 steps
The transport of molecules from the intestine into the blood stream
small intestine
Capillary
tissue cells
Explain simple diffusion and which molecules use it
Lipids and hydrophobic molecules do this
They pass through the hydrophobic layer of epithelial cells, are then divided by bile salts and made even smaller by lipase
Explain facilitated diffusion and which molecules use it
Transport which is facilitated by channel proteins through a fructose channel
Fructose and some other molecules use this
Explain active transport and which molecules use it
This requires ATP and molecules move against their concentration gradient
Glucose
Amino Acids
Na+
Ca+
Ions
Explain endocytosis and which molecules use it
Larger molecules use this and it is when the membrane of the epithelial cells engulf them
