Theme B: B3 Organisms - B3.2 Transport

Question 1

coronary arteries

Answer 1

arteries that supply blood to cardiac muscle. it feeds oxygen and nutrients directly into the muscle tissue of the heart.

Question 2

plaque

Answer 2

the build up of cholesterol and other substances in the lumen of the arteries. the restriction in blood flow causes an occluison. plaque build up is progressive amd can severely decrease the artery’s blood flow. if the occulded artery s a coronary artery, it may result in a heart attck becasue the cardiac muscle in one of more areas of the heart will be deprived of oxygen.

Question 3

cohesion-tension theory

the tension force generated by transpiration.

Answer 3

In order to bring water and dissolved minerals up from the roots, a plant relies on a tension force generated by transpiration.

Transpiration is the evaporation of water from leaves through open stomata. The water is located in the air spaces created by the spongy mesophyll layer of the leaf. The loss of water by transpiration causes water to be pulled through the cell walls of nearby xylem tissue by capillary action.

This creates tension (a negative pressure) at the upper end of each xylem tube. The tension results in the movement of water up the xylem, and the entire column of water moves up because of cohesion. This upwards movement of water with dissolved minerals is called the cohesion-tension theory.

Question 4

formation of xylem tubes

Answer 4

• Imagine many cylinder-shaped plant cells stacked up on each other to make a long tube.
• When alive these cells would have had complete cell walls, plasma membranes and typical plant cell organelles.
• Now imagine that all of these cells die leaving behind only their thick cylinder-shaped cell walls.
• Even the end walls where the cells were joined to each other in the tube completely or partially degenerate.

Question 6

lignin

Answer 6

The dead xylem tubes have cell walls fortified with lignin for strength. The lignin provides resistance to collapse of the tubes because of the tension created by transpiration. The partial or total lack of cell walls between adjoining cells of the xylem tube allows unobstructed water flow upwards. Xylem also has small pits (microscopic holes) in its sidewalls that allow the easy flow of water in and out as needed.

Question 7

Dicotyledonous

Answer 7

Dicotyledonous is one of the two categories of flowering plants: monocotyledons are the other category.

Question 8

the 5 dicotyledonous stem tissues and their functions

Answer 8

1) epidermis: prevents water loss and provides protection form microorganisms
2) cortex: an unspecialised cell layer that sometimes store food reserves
3) xylem: transport tubes that bring water up form the roots
4) phloem: transports carbohydrates, usually from leaves to other parts of the pant
5) vascular bundle: contains multiple vessels of both xylem and phloem

Question 9

tissues in a dicotyledonous root

Answer 9

1) Epidermis: Grows root hairs that increase the surface area for water uptake
2) Cortex: An unspecialized cell layer that stores food reserves
3) Xylem: Transport tubes for water and minerals, starting in the roots
4) Phloem: Transport tubes that receive sugars from leaves
5) Vascular bundle: The area in the centre of the root containing xylem and phloem

Question 10

tissue fluid

Answer 10

In order for cells to chemically exchange substances with blood, there has to be a fluid between the cells and blood. That fluid is called tissue fluid. Think of tissue fluid as the solution that bathes all cells.

tissue fluid is contsntaly renewed by being released from the side of a capillary bed closest to the arteriole.

Question 11

pressure filtration

Answer 11

within the capillary bed, blood pressure is highest at this end and the release of tissue fluid is called pressure filtration.

Question 12

difference in pressure within the capillary bed

Answer 12

The pressure at the arteriole end of the capillary bed is high enough to open gaps between the cells that make up the wall of the capillary.

At the other end of the capillary bed is the smallest of all veins, a venule. Pressure at this end of the capillary bed is relatively low because it is further away from the direct pulse of the heart. This lower pressure of the capillary bed nearer the venule allows much of the tissue fluid to drain back into the capillaries.

Question 13

chemical makeup of blood plasma and tissue fluid

Answer 13

The chemical makeup of blood plasma and tissue fluid is very similar, because of the largely unregulated passage of substances through very porous capillary membranes and gaps under arteriole pressure.
* Red blood cells and large proteins do not exit the capillaries, and thus remain in the blood stream, because they are too large to exit through the capillary walls.
* Some white blood cells are able to squeeze through capillaries into tissue fluid.