3.3 Organisms exchange substances with their environment - Digestion and Absorption Flashcards
What is the process of digestion?
Hydrolysis of large biological molecules into smaller molecules that can be absorbed across cell membranes.
Where does the digestion of carbohydrates begin?
In the mouth.
What are the two main enzymes involved in carbohydrate digestion?
- Amylases
- Membrane-bound disaccharidases.
What is the role of amylase in carbohydrate digestion?
It hydrolyses polysaccharides into the disaccharide maltose by hydrolysing glycosidic bonds.
Where is amylase produced?
- Pancreas
- Salivary glands.
What are the two membrane-bound disaccharidases mentioned?
- Sucrase
- Lactase.
What do sucrase and lactase hydrolyse into monosaccharides?
- Sucrose
- Lactose.
Fill in the blank: The digestion of carbohydrates is completed in the _______.
ileum.
What is the function of glycosidic bonds in carbohydrate digestion?
They are hydrolysed by enzymes to break down carbohydrates.
Which part of the digestive system follows the mouth in carbohydrate digestion?
Duodenum.
True or False: The ileum is where carbohydrates are first digested.
False.
List the glands that produce amylase.
- Parotid gland
- Sublingual gland
- Submandibular gland.
What is maltose?
A disaccharide produced by the hydrolysis of polysaccharides.
What are the three enzymes that hydrolyse proteins?
- Endopeptidases
- Exopeptidases
- Dipeptidases
These enzymes play different roles in the digestion of proteins.
What is the function of endopeptidases?
Hydrolyse peptide bonds between amino acids in the middle of a polymer chain.
Endopeptidases initiate the breakdown of protein by targeting internal peptide bonds.
What is the role of exopeptidases in protein digestion?
Hydrolyse peptide bonds between amino acids at the end of a polymer chain.
Exopeptidases act on the terminal ends of protein chains.
What do membrane-bound dipeptidases hydrolyse?
Peptide bonds between two amino acids.
Dipeptidases are crucial for the final stages of protein digestion.
Where does protein digestion start in the human body?
Stomach
The acidic environment of the stomach activates digestive enzymes.
In which part of the digestive system is protein digestion fully completed?
Ileum
The ileum is responsible for the absorption of nutrients after digestion.
Protein digestion continues in which part of the digestive system?
Duodenum
The duodenum receives enzymes from the pancreas that further digest proteins.
Fill in the blank: Proteins are large polymer molecules that can be _______ by three enzymes.
hydrolysed
Hydrolysis is the process of breaking down proteins into smaller peptides and amino acids.
What enzyme is responsible for the digestion of lipids?
Lipase
Lipase is produced in the pancreas.
What substance is produced in the liver that aids in lipid digestion?
Bile salts
Bile salts emulsify lipids to form tiny droplets.
What are the products of lipid digestion by lipase?
Monoglycerides and fatty acids
Lipase breaks the ester bonds in triglycerides.
What is the process called that increases the surface area of lipids for digestion?
Emulsification
Emulsification is achieved by bile salts.
What are micelles?
Tiny droplets formed from emulsified lipids
Micelles increase the efficiency of lipid digestion.
What are the two stages of lipid digestion?
- Physical (emulsification & micelle formation)
- Chemical (Lipase)
These stages enhance the digestion process.
Fill in the blank: Lipase hydrolyses lipids into _______ and fatty acids.
glycerol
Some monoglycerides may also be produced.
True or False: Bile salts are produced in the pancreas.
False
Bile salts are produced in the liver.
What is the role of bile salts in lipid digestion?
To emulsify lipids
This creates small droplets for enhanced lipase action.
What is the significance of increasing the surface area of lipids during digestion?
Enables faster hydrolysis by lipase
More surface area allows lipase to act more effectively.
What are micelles?
Water-soluble vesicles formed from fatty acids, glycerol, monoglycerides, and bile salts.
Bile salts make the fatty acids and micelles water-soluble.
What is the role of micelles in digestion?
They deliver fatty acids, glycerol, and monoglycerides to the epithelial cells of the ileum for absorption.
How do fatty acids and monoglycerides enter epithelial cells?
Via simple diffusion due to being non-polar and lipid-soluble.
What is formed when fatty acids link together?
Triglycerides.
Where does the absorption of digestion products occur in mammals?
Across the cells lining the ileum.
What structures increase the absorption surface area in the ileum?
Villi and microvilli.
What is the function of villi in the ileum?
To maximize absorption by increasing surface area.
What is the significance of the thin walls of the ileum?
They decrease the diffusion distance.
What maintains a steep concentration gradient in the ileum?
The network of capillaries surrounding the epithelial cells.
Fill in the blank: Micelles are formed from _______.
[fatty acids, glycerol, monoglycerides, bile salts]
True or False: Microvilli are larger than villi.
False.
What are lipids digested into?
Monoglycerides and fatty acids
What enzymes are involved in lipid digestion?
Lipase and bile salts
What are the tiny structures formed during lipid digestion called?
Micelles
How do fatty acids and monoglycerides enter epithelial cells?
By simple diffusion across the cell surface membrane
Where are triglycerides modified back after entering the epithelial cells?
Inside the endoplasmic reticulum and Golgi body
What are chylomicrons formed from?
Fatty globules combining with proteins
Where do chylomicrons enter after being extruded from the epithelial cell?
A lacteal (lymph capillary)
Fill in the blank: Fatty acids link to form _______.
Triglycerides
True or False: Micelles can easily diffuse into epithelial cells due to the non-polar nature of fatty acids and monoglycerides.
True
What transports chylomicrons away from the intestine?
Lymph in the lacteal
What is the primary purpose of co-transport in digestion?
To absorb glucose and amino acids from the lumen to the gut
What must be true for facilitated diffusion of glucose and amino acids?
Higher concentration of glucose and amino acids in the lumen compared to the epithelial cell
Why is active transport needed for glucose and amino acid absorption?
There is usually more glucose in the epithelial cells
What is the first step in the co-transport process of glucose and amino acids?
Sodium ions are actively transported out of the epithelial cell into the blood in the capillary
What effect does the active transport of sodium ions have on their concentration in the epithelial cell?
It reduces the sodium ion concentration in the epithelial cell
How do sodium ions move back into the epithelial cell?
They diffuse from the lumen down their concentration gradient
What type of protein do sodium ions diffuse through during co-transport?
Co-transporter protein
What additional molecules can be transported into the epithelial cell along with sodium ions?
Glucose or amino acids
How do glucose or amino acids move from the epithelial cell to the blood?
By facilitated diffusion
Fill in the blank: Sodium ions are actively transported out of the epithelial cell into the _______.
blood
True or False: Co-transport allows glucose and amino acids to be transported into epithelial cells against their concentration gradient.
True
What is the end result of digestion?
Digestion ends with the release of smaller biological molecules.
What are peristalsis and its role in digestion?
Peristalsis is the muscular contraction that moves food through the digestive tract.
What are the main types of enzymes involved in digestion?
Digestive enzymes include amylases, proteases, and membrane-bound lipases.
How are amino acids and glucose absorbed in the small intestine?
Absorption of amino acids and glucose is by co-transport.
What links digestion to biological molecules?
Digestion links to biological molecules through hydrolysis.
How does the absorption of lipids relate to cell organelles?
Absorption of lipids links to the function of cell organelles.
What is the connection between digestion and enzyme action?
Digestion links to enzyme action through the breakdown of food.
What types of transport are involved in the absorption of glucose and amino acids?
Absorption links to transport across membranes - active and co-transport.
Fill in the blank: Digestion links to _______ through hydrolysis.
[biological molecules]
True or False: Peristalsis is a chemical process involved in digestion.
False
What is required for facilitated diffusion of glucose and amino acids from the lumen to the gut?
A higher concentration of glucose and amino acids in the lumen compared to the epithelial cell
Why is active transport needed for the absorption of glucose and amino acids?
There is usually more glucose in the epithelial cells than in the lumen
What is the first step in the co-transport process of glucose and amino acids?
Sodium ions are actively transported out of the epithelial cell into the blood in the capillary
What effect does the active transport of sodium ions have on their concentration in the epithelial cell?
It reduces the sodium ion concentration in the epithelial cell
How do sodium ions move back into the epithelial cell?
By diffusing down their concentration gradient from the lumen
What type of protein do sodium ions diffuse through during co-transport?
Co-transporter protein
What additional molecules can attach to the co-transporter protein along with sodium ions?
Glucose or amino acids
What is the process by which glucose or amino acids move from the epithelial cell to the blood?
Facilitated diffusion
Fill in the blank: Sodium ions are actively transported out of the epithelial cell into the _______.
blood in the capillary
True or False: Sodium ions can diffuse into the epithelial cell against their concentration gradient.
False
List the key terms associated with the co-transport of glucose and amino acids.
- Epithelial cell
- Sodium ions
- Glucose
- Amino acids
- Concentration gradient
What is the primary function of digestion?
To break down food into smaller, absorbable components.
What are peristalsis and its role in digestion?
Peristalsis is the wave-like muscle contractions that move food through the digestive tract.
What are the types of enzymes involved in digestion?
Digestive enzymes include amylases, proteases, and lipases.
How are amino acids and glucose absorbed?
By co-transport mechanisms.
Fill in the blank: Absorption of lipids links to the function of _______.
cell organelles
How does digestion relate to biological molecules?
Digestion links to biological molecules through hydrolysis.
What links enzyme action to digestion?
The breakdown of food by enzymes.
What types of transport are involved in the absorption of glucose and amino acids?
Active transport and co-transport.
True or False: Digestion does not involve enzyme action.
False
What are the roles of digestive enzymes?
- Break down carbohydrates
- Break down proteins
- Break down lipids
What is hydrolysis in the context of digestion?
The chemical breakdown of a compound due to reaction with water.
List the main components involved in the process of digestion.
- Enzymes
- Muscle contractions
- Biological molecules
What is the significance of membrane-bound enzymes in digestion?
They help to digest nutrients directly at the site of absorption.
