3.3-4(P2) Digestion&Absorption/MT in Plants

Question 1

We do we need to digest polymers?

Answer 1

To break them down into monomers

So we can absorb them into our cells either physically or chemically

Question 2

What is physical digestion?

Answer 2

Teeth - mastication

Stomach - churns food

Question 3

What is chemical digestion?

Answer 3

Large insoluble molecules broken down into small soluble molecules by enzymes in the process of hydrolysis

Question 4

Describe general break down to absorption?

Answer 4

Bolus - food blob
Chyme - liquid, broken down in stomach
Any chyme not absorbed in the small intestine will be sent to the large intestine

Question 5

What substrate does amylase catalyse to form what product?

Site of production and digestion?

Answer 5

Substrate: starch

Products: maltose

Site of production: salivary glands and pancreas

Site of digestion: mouth and duodenum

Question 6

What substrate does maltase catalyse to form what product?

Site of production and digestion?

Answer 6

Substrate: maltose

Products: glucose

Site of production: epithelial lining of ilium

Site of digestion: epithelial lining of ilium

Question 7

What substrate does sucrase catalyse to form what product?

Site of production and digestion?

Answer 7

Substrate: sucrose

Products: glucose and fructose

Site of production: epithelial lining of ilium

Site of digestion: epithelial lining of ilium

Question 8

What substrate does lactase catalyse to form what product?

Site of production and digestion?

Answer 8

Substrate: lactose

Products: glucose and galactose

Site of production: epithelial lining of ilium

Site of digestion: epithelial lining of ilium

Question 9

What substrate does lipase catalyse to form what product?

Site of production and digestion?

Answer 9

Substrate: triglyceride

Products: glycerol and 3 fatty acid chains

Site of production: pancreas

Site of digestion: duodenum

Question 10

What substrate does endopeptidase catalyse to form what product?

Site of production and digestion?

Answer 10

Substrate: polypeptides

Products: polypeptides and dipeptides

Site of production: stomach and pancreas

Site of digestion: stomach and duodenum

Question 11

What substrate does exopeptidase catalyse to form what product?

Site of production and digestion?

Answer 11

Substrate: polypeptides and dipeptides

Products: dipeptides and amino acids

Site of production: pancreas

Site of digestion: duodenum

Question 12

What substrate does dipeptidase catalyse to form what product?

Site of production and digestion?

Answer 12

Substrate: dipeptides

Products: amino acids

Site of production: epithelial lining of ilium

Site of digestion: epithelial lining of ilium

Question 13

What is the difference between endopeptidase and exopeptidase?

Answer 13

Endopeptidase - works in the middle of a polypeptide chain

Exopeptidase - works at the end of a polypeptide chain

Question 14

What is used to increase efficiency in absorbing products of digestion?

Answer 14

Villi and microvilli are present in the small intestine

Question 15

What are some adaptations of villi?

Answer 15

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

Question 16

How are amino acids absorbed into the blood from cells?

Answer 16

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

Question 17

What is the micelles role in the absorption of lipids?

Answer 17

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

Question 18

Describe the path of water and molecules into tissue and tissue fluid?

Answer 18

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

Question 19

Describe the path of water and molecules out of the tissue and tissue fluid?

Answer 19

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

Question 20

What are some fluid related diseases?

Answer 20

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)

Question 21

Why does a lack of protein in kwashiorkor lead to an abdominal oedema?

Answer 21

Less protein in the blood means the osmotic concentration gradient is smaller therefore less water will move out of the cell

Question 22

How is water absorbed into root hair cells?

Answer 22

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

Question 23

What is an apoplastic and symplastic pathway?

Answer 23

Apoplastic - constant stream of water molecules moving through the cell wall

Symplastic - water molecules moving through the cytoplasm through many plasmodesmata

Question 24

How does water move through a leaf?

Answer 24

Evaporation of water via the stomata pulls more water through from the xylem (steep concentration gradient)

Question 25

How does water move through a plant?

Answer 25

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

Question 26

What factors effect the rate of transpiration?

Answer 26

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

Question 27

What is translocation?

Answer 27

Sugars made in the leaves need transporting to other regions of the plant

Question 28

Describe the first 2 stages of translocation?

Answer 28

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

Question 29

Describe the middle stages of translocation?

Answer 29

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

Question 30

Describe the last stage of translocation?

Answer 30

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

Question 31

What is used to measure uptake of water?

Calculation?

Answer 31

Potometer

Speed of air bubble x cross sectional area of capillary tube

Question 32

What is the reservoir used for in a potometer?

Answer 32

To make repeat measurements by forcing the bubble back to the right

Question 33

In a potometer why is rate of water uptake not equivalent to rate of transpiration?

Answer 33

Plant retains some water for photosynthesis

Plant releases some water via respiration