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Biology IB HL - 6.1 Digestion Part 4
This flashcard deck covers key concepts related to digestion in the Biology IB HL curriculum, focusing on the structure and function of the digestive system, absorption mechanisms, and transport processes.
What is the role of tight junctions?
They keep digestive fluids separated from tissues and maintain a concentration gradient by ensuring one-way movement
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Key Terms
Term
Definition
What is the role of tight junctions?
They keep digestive fluids separated from tissues and maintain a concentration gradient by ensuring one-way movement
What is the role of microvilli?
Microvilli borders significantly increase surface area of the plasma membrane (>100×), allowing for more absorption to occur
What may be embedded upon microvilli?
The membrane will be embedded with immobilised digestive enzymes and channel proteins to assist in material uptake
What type of organelle do epithelial cells of intestinal villi have a lot of?
Epithelial cells of intestinal villi will possess large numbers of mitochondria to provide ATP for active transport mechanisms
Why do intestinal cells have a lot of mitochondria?
ATP may be required for primary active transport (against gradient), secondary active transport (co-transport) or pinocytosis
What is pinocytosis?
Pinocytosis (‘cell-drinking’) is the non-specific uptake of fluids and dissolved solutes (a quick way to translocate in bulk)
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| Term | Definition |
|---|---|
What is the role of tight junctions? | They keep digestive fluids separated from tissues and maintain a concentration gradient by ensuring one-way movement |
What is the role of microvilli? | Microvilli borders significantly increase surface area of the plasma membrane (>100×), allowing for more absorption to occur |
What may be embedded upon microvilli? | The membrane will be embedded with immobilised digestive enzymes and channel proteins to assist in material uptake |
What type of organelle do epithelial cells of intestinal villi have a lot of? | Epithelial cells of intestinal villi will possess large numbers of mitochondria to provide ATP for active transport mechanisms |
Why do intestinal cells have a lot of mitochondria? | ATP may be required for primary active transport (against gradient), secondary active transport (co-transport) or pinocytosis |
What is pinocytosis? | Pinocytosis (‘cell-drinking’) is the non-specific uptake of fluids and dissolved solutes (a quick way to translocate in bulk) |
How will liquids be absorbed by pinocytosis? | These materials will be ingested via the breaking and reforming of the membrane and hence contained within a vesicle |
During absorption, where must digested food molecules go? | During absorption, digested food monomers must pass from the lumen into the epithelial lining of the small intestine |
What is the only option of where the digested food monomers may go and why? | Tight junctions between epithelial cells occlude any gaps between cells – all monomers must cross the membrane |
Do all monomers travel the same way during absorption? | NO| Different monomers undertake different methods for crossing the apical and basolateral membranes |
What 4 ways may digested food monomers move across a membrane? | secondary active transport; facilitated diffusion; osmosis; simple diffusion |
How does secondary active transport work? | A transport protein couples the active translocation of one molecule to the passive movement of another (co-transport) |
What is transported via secondary active transport? | Glucose and amino acids are co-transported across the epithelial membrane by the active translocation of sodium ions (Na+) |
What is the role of facilitated diffusion? | Channel proteins help hydrophilic food molecules pass through the hydrophobic portion of the plasma membrane |
Where are channel proteins usually located? | Channel proteins are often situated near specific membrane-bound enzymes (creates a localised concentration gradient) |
What is transported by facilitated diffusion? | Certain monosaccharides (e.g. fructose), vitamins and some minerals are transported by facilitated diffusion |
What is absorbed via osmosis? | Water molecules will diffuse across the membrane in response to the movement of ions and hydrophilic monomers (solutes) |
Where does the absorption of water and dissolved ions occur? | The absorption of water and dissolved ions occurs in both the small and large intestine |
How does simple diffusion function? What travels via simple diffusion? | Hydrophobic materials (e.g. lipids) may freely pass through the hydrophobic portion of the plasma membrane |
How are lipids transported once absorbed? | Once absorbed, lipids will often pass first into the lacteals rather than being transported via the blood |
What does endocytosis involve? | method of bulk transport
Endocytosis involves the invagination of the plasma membrane to create an internal vesicle containing extracellular material |
What does vesicle formation during endocytosis require? | Vesicle formation requires the breaking and reforming of the phospholipid bilayer and hence is an energy-dependent process |
In the intestines where does endocytosis usually occur? | In the intestines, vesicles commonly form around fluid containing dissolved materials (pinocytosis – cell ‘drinking’) |
What is the purpose of pinocytosis? | Pinocytosis allows materials to be ingested en masse and hence takes less time than shuttling via membrane proteins |
In what forms can starch be found? | Starch can exist in one of two forms – linear chains (amylose) or branched chains (amylopectin) |