Proteins, Digestion And Absorption Flashcards
How do all digestive enzymes function?
All digestive enzymes function by hydrolysis.
Why is more than one enzyme usually required to hydrolyse a large molecule.
Enzymes = specific, so therefore, more than one enzyme is needed to hydrolyse a large molecule.
Usually one enzyme hydrolyses large molecule into sections.
These sections = then broken down further by one or more additional enzymes into smaller molecules.
Why does the stomach not have villi or microvilli?
Villi/microvilli increase surface area for maximum absorption but in the stomach, food molecules haven’t yet been hydrolysed into soluble material so there is no use in villi/microvilli in the stomach.
What are the 2 stages of digestion?
Physical breakdown.
Chemical digestion.
What happens in the physical breakdown stage of digestion?
Large food is broken down into smaller pieces by structures like teeth - ingestion of food = possible + = a larger surface area for chemical digestion.
Food is churned by stomach wall for further break down.
What happens in the chemical digestion stage in digestion?
Hydrolyses large molecules into smaller molecules by enzyme which function by hydrolysis (adding water to split molecules up).
One enzyme hydrolyses a large molecule into smaller parts which many other enzymes act on.
What are the 3 most important types of digestive enzymes?
Carbohydrases. (Carbohydrates –> monosaccharides)
Lipases. (Lipids –> Glycerol + fatty acids)
Proteases. (Proteins –> amino acids)
How are lipids digested?
Lipids = broken up into micelles first by bile salts in process called emulsification - increases SA so lipase action = sped up.
Lipases hydrolyse ester bond in triglycerides to form monoglycerides (single glycerol molecule + one fatty acid) + fatty acids.
Where are bile salts produced?
Liver.
How are carbohydrates digested?
Amyloses hydrolyses alternate glycosidic bonds of starch molecule = maltose produced = hydrolysed to form alpha glucose by maltase produced in the lining of the ileum.
What is diffusion’s role in absorption?
Carbohydrates + proteins = digested continuously. Greater conc. of glucose/amino acids in ileum than blood, .: they move down conc. gradient by facilitated diffusion from ileum -> blood.
How is the diffusion gradient maintained in absorption?
Blood constantly circulated by heart. Glucoses absorbed by cells continuously - need it for respiration. Maintain conc. gradient between ileum + blood, .: rate of diffusion increases.
What is active transport’s role in absorption?
Diffusion = conc. either side of ileum are equal. Active transport ensures all available glucose + aa are absorbed. So are absorbed from ileum by co-transport as sodium ions are drawn out by sodium-potassium pump.
How does the sodium-potassium pump work?
- Sodium ions actively transported out of epithelial cells by sodium-potassium pump.
