3.3-4(P2) Digestion&Absorption/MT in Plants Flashcards
We do we need to digest polymers?
To break them down into monomers
So we can absorb them into our cells either physically or chemically
What is physical digestion?
Teeth - mastication
Stomach - churns food
What is chemical digestion?
Large insoluble molecules broken down into small soluble molecules by enzymes in the process of hydrolysis
Describe general break down to absorption?
Bolus - food blob
Chyme - liquid, broken down in stomach
Any chyme not absorbed in the small intestine will be sent to the large intestine
What substrate does amylase catalyse to form what product?
Site of production and digestion?
Substrate: starch
Products: maltose
Site of production: salivary glands and pancreas
Site of digestion: mouth and duodenum
What substrate does maltase catalyse to form what product?
Site of production and digestion?
Substrate: maltose
Products: glucose
Site of production: epithelial lining of ilium
Site of digestion: epithelial lining of ilium
What substrate does sucrase catalyse to form what product?
Site of production and digestion?
Substrate: sucrose
Products: glucose and fructose
Site of production: epithelial lining of ilium
Site of digestion: epithelial lining of ilium
What substrate does lactase catalyse to form what product?
Site of production and digestion?
Substrate: lactose
Products: glucose and galactose
Site of production: epithelial lining of ilium
Site of digestion: epithelial lining of ilium
What substrate does lipase catalyse to form what product?
Site of production and digestion?
Substrate: triglyceride
Products: glycerol and 3 fatty acid chains
Site of production: pancreas
Site of digestion: duodenum
What substrate does endopeptidase catalyse to form what product?
Site of production and digestion?
Substrate: polypeptides
Products: polypeptides and dipeptides
Site of production: stomach and pancreas
Site of digestion: stomach and duodenum
What substrate does exopeptidase catalyse to form what product?
Site of production and digestion?
Substrate: polypeptides and dipeptides
Products: dipeptides and amino acids
Site of production: pancreas
Site of digestion: duodenum
What substrate does dipeptidase catalyse to form what product?
Site of production and digestion?
Substrate: dipeptides
Products: amino acids
Site of production: epithelial lining of ilium
Site of digestion: epithelial lining of ilium
What is the difference between endopeptidase and exopeptidase?
Endopeptidase - works in the middle of a polypeptide chain
Exopeptidase - works at the end of a polypeptide chain
What is used to increase efficiency in absorbing products of digestion?
Villi and microvilli are present in the small intestine
What are some adaptations of villi?
Large SA created by microvilli
Steep concentration gradient from Constant blood flow - O2 being used up in aerobic respiration (internal medium)
Chyme moving through the small intestine (external medium)
Short diffusion distance as one cell thick and a large network of capillaries directly next to the villi
How are amino acids absorbed into the blood from cells?
Co transport
Sodium is actively transported out of the cell (potassium is brought in) leading to a decrease in sodium concentration in the cell
Facilitated diffusion of sodium into the cell also brings amino acids in
As the amino acid concentration increases in the cell it will diffuse out into the blood
What is the micelles role in the absorption of lipids?
Fatty acids and monoglycerides leave micelles which enter an epithelial cell
Fatty acids link to form triglycerides
In the Golgi apparatus fatty globules combine with proteins to form chylomicrons
Chylomicrons leave the epithelial cell into a lacteal or lymph capillary
The lymph capillary transports the chylomicrons from the intestine
Describe the path of water and molecules into tissue and tissue fluid?
Blood has a high hydrostatic pressure: high O2, H2O, glucose, salts and proteins
High pressure forces all but proteins, WBC and RBC into the fluid as they are too big to pass out
Small molecules called ultrafiltration leave the blood
Now blood has a lower water potential as water moved out
Describe the path of water and molecules out of the tissue and tissue fluid?
Via osmosis the water moves back into the blood as the hydrostatic pressure is lower than the osmotic pressure in the fluid
CO2 now diffuses into the blood
Excess fluid drains out of the over flow tap (lymph vessel) which rejoins the blood near the vena cava
What are some fluid related diseases?
Oedema - fluid retention causing swollen tissue (more noticeable in legs because of gravity)
Kwashiorkor - malnutrition from lack of protein (pot belly look as oedema in abdomen)
Elephantiasis - oedema from infection of parasitic worm in lymph vessel (blocks drainage tap)
Why does a lack of protein in kwashiorkor lead to an abdominal oedema?
Less protein in the blood means the osmotic concentration gradient is smaller therefore less water will move out of the cell
How is water absorbed into root hair cells?
Water moves in via osmosis as there is a higher water potential outside the cell and lower inside due to the vacuole (sugary cell sap)
Short diffusion distance as it’s a think cellulose cell wall
SA:V ratio is large as the root hair cell is long and thin
Mineral ions moved in by active transport lower the water potential further drawing more water in
What is an apoplastic and symplastic pathway?
Apoplastic - constant stream of water molecules moving through the cell wall
Symplastic - water molecules moving through the cytoplasm through many plasmodesmata
How does water move through a leaf?
Evaporation of water via the stomata pulls more water through from the xylem (steep concentration gradient)
How does water move through a plant?
Transpiration
Water is PULLED due to evaporation out the stomata
Water is PUSHED from the root pressure building up as more water is take in via osmosis
What factors effect the rate of transpiration?
High wind - maintains concentration gradient carries moisture from immediate air
High temperature - provides kinetic energy for particles to evaporate quicker
Low humidity- dry conditions keeps concentration gradient as less water around the leaves
What is translocation?
Sugars made in the leaves need transporting to other regions of the plant
Describe the first 2 stages of translocation?
Sucrose that is made via photosynthesis from glucose creates a high concentration gradient so the sucrose will diffuse from the source (leaf) into a companion cell adjacent to phloem
The sucrose is moved via co-transport with hydrogen ions into the phloem sieve tubes - lowering the water potential inside the phloem which draws water in from the xylem to the phloem via osmosis
Describe the middle stages of translocation?
Water now in the phloem creates a high hydrostatic pressure in upper regions of the phloem so the sucrose solution moves down the pressure gradient
Sucrose at sink cells (destination) is used in respiration - sucrose is moved in via active transport as it is quicker than relying on diffusion allowing the transport to be constant
Describe the last stage of translocation?
As the water potential of respiring cells is low (due to the sucrose that has been actively transported in) water moves in
Therefore the pressure in the phloem at the sink is always lower than at the source ensuring the constant movement of substances down the phloem tube
What is used to measure uptake of water?
Calculation?
Potometer
Speed of air bubble x cross sectional area of capillary tube
What is the reservoir used for in a potometer?
To make repeat measurements by forcing the bubble back to the right
In a potometer why is rate of water uptake not equivalent to rate of transpiration?
Plant retains some water for photosynthesis
Plant releases some water via respiration
