Chapter Two : Transport

The main concepts of Chapter Two:
Transport in living organisms

1- In primitive plants raw materials and products of photosynthesis move from one cell to another by osmosis, diffusion and active transport.

2- In higher plants gases move by diffusion, mineral salts and soluble products of photosynthesis are transported through vascular tissues "xylem and phloem".

3- Xylem and phloem extend from the root, through the stem to the leaves.

4- Xylem transports water and mineral salts from the root to the leaves as well as it supports the plant.

5- The young dicot stem consists of the following tissues:
- epidermis
- cortex
- vascular cylinder which consists of
1- Pericycle 2- pith
3- Medullary rays 4- vascular bundels
Each vascular bundel consists of phloem - xylem - cambium

6- Stem cortex consists of collenchyma and parenchyma.

7- The Xylem tissue consists of cylindrical elongated cells called vessels and pentagonal or hexagonal tubes called trachieds.

8- Pith are unlignified sites found on the primary cellulose wall.

9- Xylem vessels and tracheids have lignin deposits which take the form of annular - spiral - reticulate and scalari form.

10- There are many different theories which explain the ascent of water in the plant; these theories are:
a- The root pressure theory.
b - Imbibition theory
c- Capillary theory
d- Cohesion - adhesion transpiration pull.

11- Exudation it is the natural phenomenon through which the water comes out if the stem is cut near the soil (root).

12- The embibition theory states that the colloidal nature of cellulose and lignin helps the walls of xylem to imbibe the water, this theory has a limited effect on the ascent of sap.

13- Water rises up through tiny tubes against gravity by capillarity, it has a limited effect on the ascent of sap.

14- Cohesion - adhesion and transpiration pull was explained by Dixon and Joly in 1895 it states that the ascent of water through xylem vessels depends upon three forces, cohesive force which is the strong mutual attraction between water molecules, adhesive force which is the attraction between water molecules and xylem molecules, which holds the water column against gravity; transpiration pull of the leaf which is the continuous process of transpiration in the leaves attracts or pulls the water column upwards.

15- The conditions that are necessary for the ascent of sap in xylem are:
- free of any gas babbles
- capillary tubes
- the wall should be of colloidal nature.

16- The phloem consists of sieve tubes, companion cell, and phloem parenchyma.

17- Cytoplasmic streaming is the circular movement of the cytoplasm inside the sieve tubes and the companion cells. It is affected by the amount of oxygen and the temperature.

18- The process of transport takes place in the human body through two systems which are:
a- The circulatory system.
b - The lymphatic system.

19- The circulatory system in man consists of the heart, the blood vessels and the blood.

20- The heart is a hollow muscular organ, it lies nearly in the middle of the chest cavity, it is enclosed by a pericardium membrane.

21- The heart consist of two thin walled upper chambers called atria and two thick walled lower chambers called ventricles.

22- The tricuspid valve between right atrium and right ventricle is made up of three flaps.

23- The Bicuspid valve (mitral) between left atrium and left ventricle made up of two flaps.

24- Blood vessels consists of:
a- Artries, b- veins, c- capillaries

25- Both artries and veins consists of three layers:
a- outer connective tissue
b - middle unstriated muscle fibers.
c- inner endothelium

26- Artries are more elastic than veins, they pulsate and buried deep in muscles.

27- Veins have internal valves to prevent the back flow of the blood.

28- The human blood is about 5.6 litre, it consists of plasma 54%, red blood cells, white blood cells and platelets.

29- Red blood cells are about 5 millions/mm³. They have the haemoglobin which combines with oxygen and carbon dioxide.

30- White blood cells which are about 7000/ mm³, they protect the body against infections diseases.

31- The red blood cells are produced from the bone marrow (every 120 days.)

32- The white blood cells are produced from the bone marrow and lymphatic nodes.

33- The blood plasma consists mainly of water, inorganic salts, proteins and other components.

34- Blood has many functions:
a- Transports digested food, oxygen, CO₂, nitrogenous compounds, hormones and enzymes.
b - It controls the metabolism process and keeps body temp. at 37 ^oC.
c- It regulates the internal environment.
d- It protects the body against microbes.
e- It stops bleeding by clot formation.

35- The rhythmic heart beats are spontaneous i.e. they originate from the cardiac tissue itself.

36- The sino - atrial node acts are pace - maker, it is joined to two nerves:
a- vagus nerve which slows down heart beats.
b - Sympathetic nerve which accelerates heart beats.

37- The number of heart beats is affected by some factors that it decreases during sleeping and increases during physical effort and in case of Joy.

38- Two sounds in the heart beats are distinguished:
1- long and low pitched due to the closure of the tricuspid and bicuspid valves.
2- Short and high pitched due to the closure of aortic and pulmonary valves.

39- There are three blood circulations:
A- pulmonary circulation which starts from right ventricle and ends at the left atrium.
B - systematic circulation which starts at the left ventricle and ends at the right atrium.
C - Hepatic portal circulation: when glucose and amino acids are absorbed by the villi and pour their contents into the liver cells.

40- The mechanism of blood clot.

41- Blood does not clot inside blood vessels because the liver secretes heparin which prevents the conversion of prothrombin to thrombin.

 

Chapter three

The main concepts of Chapter three:
Concept of Respiration

 

1- A T P molecule is built up of three subunits which are Adenine, Ribose and three phosphate groups.

2- One A T P molecule is hydrolyzed into A D P and about 7 - 12 k cal.

3- Oxidation of glucose can be summarized by the following equation:

4- Oxidation of glucose takes place into two stages:
A- Glycolysis in the Cytosol
B - Respiration which divided into:
- krebs cycle, - electron transport.

5- The mitochondria are the centers of respiration in the cell.

6- Oxidation is loss of electrons and reduction is the gain of electrons.

7- NAD⁺ is a co-enzyme which can receive a proton and two electrons to be reduced to NADH₂.

8- Co-enzyme FAD⁺ can receive two protons and two electrons to be FADH₂

9- Cytochromes are electron acceptors which are similar in structure and carry electrons at different energy levels.

10- Through krebs cycle acetyl COA joins krebs cycle where its coA-enzyme splits off to repeat its role, at the same time the acetyl group combines with oxaloacetic acid to form citric acid.

11- Krebs cycle does not need oxygen because all the electrons and protons are received by NAD⁺ and FAD⁺

12- Oxidative phosphorylation is a conversion process from ADP and phosphorus into ATP.

13- Through electron transport, 3 molecules of ATP are formed every time a pair of electrons is transferred through the entire carrier system.

14- Anaerobic respiration or fermentation is a process through which living organisms break down food molecule to release energy in the absence of oxygen or in low quantity.

15- Anaerobic respiration starts with glycolysis to form pyruvic acid which may be changed into ethyl alcohol in case of yeast fungus or lactic acid in case of animal muscles or several kinds of bacteria.

16- The released energy from aerobic respiration is 38 ATP while that of anaerobic respiration is only 2 ATP.

17- The respiration system in man consists of:
- Nose
- Pharynx
- Larynx
- Trachea
- Bronchi
- Bronchioli
- Air sacs.

18- It is better to breath through the nose because it contains hairs, blood capillaries and secretes mucus.

19- Alveoli have very thin walls surrounded with a network of blood capillaries to make gas exchange easier.

20- Alveoli bronchioli and capillaries together form the lung.

21- Diaphragm is a respiratory muscle that participates in the mechanism of respiration.

22- During inspiration, the rib muscles and diaphragm muscle contract, so the size of the chest cavity increases and the internal air pressure decreases so the outside air flows into the lungs.

23- During expiration, the rib muscles and diaphragm relax decreasing the chest cavity and increasing the internal pressure so the air is forced outside the lungs.

24- A part of air is always left inside the lung to warm the new coming air to make adhesion of the alveoli membranes with the walls of blood capillaries to ease gas exchange.

25- During each respiratory cycle the aeration of lungs not usually exceed 10% of its capacity, this ratio varies according to the rate of individual activity and depth of inspiration.

26- The respiratory system in man plays an important role in the excretion of water in the form of water vapour.

27- Man usually loses daily about 500 mL of water through his lungs out of 2500 mL of water that he lost daily.

28- Water inside alveoli helps to moisten the alveoli membrane and also necessary for dissolving oxygen and carbon dioxide, so the gas exchange occurs easily.

29- Respiration in plants may be aerobic respiration or anaerobic respiration.

30- In case of vascular plants, oxygen reaches the cell through various passage ways such as:
A- stomata of the leaf.
B- Through the phloem.
C_ Oxygen may enter the plant through the root.
D- green plant stem has stomata so oxygen may enter through them.
E - woody plant stem has lenticels or cracks through which oxygen may pass.

31- CO₂ which is resulted from respiration of the plant may be expelled out through:
A- Diffusion if plant cells are directly in contact with air.
B - Deep cells pass CO₂ to xylem and phloem to carry it to stomata
C- A part of CO₂ is used in photosynthesis.