
Chapter One : Nutrition
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Unit Two - Two Terms |
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Unit Three - Two Terms |
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Unit Four (cancel) - Two Terms |
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Chapter One : Nutrition
The
main concepts
Chapter 1: Nutrition
1-
Nutrition is the study of food and various modes of feeding in living
organisms.
2- Living organisms may be :-
- Autotrophic
[photoautotrophs or chemoautotroph.
- Heterotrophic
3-
Autotrophic nutrition in green plants includes:-
- Absorption
of water and salts.
- Photosynthesis.
4- The
different tissues of the root are:-
- Epidermis
- Cortex
- Endodermis
- Vascular cylinder which consists of
pericycle- xylem - phloem - pith .
5- The root hairs are
well adapted to their function that: -
- They have thin walls
- They are large in number
- The solution in their
vacuoles is more concentrated. ,BR> - They secrete a viscous
substance.
6- Diffusion:
It is the movement of a
substance from highly concentrated medium to a lower concentrated
one.
7- Osmosis:
It is the diffusion of water from
a diluted medium of high water concentration to another of lower
water concentration through a semipermeable membrane.
8-
Permeability:-
It is the ability of cell walls and cell
membranes to pass substances through them.
9- Imbibition:
It is the ability of solid particles especially colloidal ones
to absorb liquids and increase in volume.
10- The
absorbed water passes through the root cells until it reaches xylem
vessels in three pathways:
A- Cell walls by imbibition.
B-
Through the cytoplasm and plasmodesmata.
C- Cell sap by
osmosis.
11- The root hairs of desert plants (xerophytes)
reaches 50 - 200 atmospheres while that of the ordinary plants
(mesophytes) ranges from 5 to 20 atmospheres.
12- The
endodermis has a major role in controlling the passage of both water
and solutes to the xylem vessels that the cells that face the phloem
are completely thickened with suberin, while those facing the xylem
which we call passage cells have impermeable ribbon of suberin called
casparian strip.
13- Essential elements for green plants
are divided into:
A- Macro - nutrients N, P, K, Ca, Mg, S, Fe
B- Micro-nutrients:
Mn, Zn, B, Cl, Cu, Mo, I, Al which
act as co-enzymes that they activate enzymes.
14- Active
transport:
It is the passage of any substance through the cell
membrane against concentration gradients, with the help fo chemical
energy released during aerobic respiration.
15- Cation
exchange.
The root cells may get rid of some positive ions like
Na+
and replace them by K+
ions this is done according to the cell needs.
16-
Photosynthesis is important because it provides food for all living
organisms, gives oxygen, some plant fibers are used in some
industries as well as fossil fuels were originated from plants.
17-
The raw materials required for photosynthesis:
a- water as a
source of Hydrogen.
b- nitrates, sulphates, phosphates are
needed to convert carbohydrates into proteins.
c- phosphorus to
build A T P.
d- Magnesium for chlorophyll synthesis.
e-
Iron as co-enzyme.
18- Products of photosynthesis:
a-
monosaccharide "glucose"
b- Oxygen.
19-
The rate of photosynthesis can be determined by two ways.
a- By
measuring the amount of starch built in a unite time.
b- By
counting the number of oxygen bubbles evolved.
20- The
normal rate of photosynthesis is gram / hour / meter square of the
green leaf.
21- The chloroplasts are the sites of
photosynthesis.
22- Each chloroplast is enclosed by a
thin double membrane, disc-shaped structures called grana are
embedded in the stoma.
23- There are 4 main Pigments
inside the hollow of the grana, these are chlorophyll A and B,
Xanthophyll and Carotine.
24- The chemical structure of
the chlorophyll is N4
MG
25- Plant leaves are well adapted for their function,
that, they are arranged in a parallel way, the blade is thin and
flattened, the blade is supported by a mid rube as well as protective
hairs may grow on the surface of some plant leaves and their tips.
26- The plant leaf consists of three main tissues:
a-
The epidermis "upper and lower"
b- The mesophyll
"palisade and spongy"
c- The vascular tissue "xylem
and phloem"
27- Van Neil studied photosynthesis is
both green and purple bacteria.
28- Green and purple
bacteria use H2S
31-
Water is the source of oxygen released from photosynthesis
34-
Photosynthesis includes two main stages.
A- Light reactions in
which the light is the limiting factor, through which light is
absorbed by
A- Chlorophyll A and energy which is released from
its electrons are used to split water into oxygen and hydrogen and
the rest is used to convert
to
store energy.
B - Dark reactions:
In which CO2
is reduced by hydrogen (NADPH2
) with the help of energy stored in A T P to form monosaccharide
glucose these reactions are controlled by temperature and enzymes.
35- Digestion is the change of large molecules polymers
into smaller one monomers by hydrolysis.
36- Enzymes are
protenic substances that act as catalyst which activate a particular
chemical reaction.
37- Enzymes are highly specific, some
have a reversible action, some are secreted in inactive form, and
each enzyme has a certain pH to work or to be active.
38-
The digestive system in man consists of two main parts:
A - The
alimentary canal which starts with the mouth and ends with anus.
B
- Associated or accessory glands which produce digestive juices that
help in digestion.
39- The different organs of the
alimentary canal are:
- The mouth
- The pharynex
-
The oesophagus
- The stomach
- The small intestine
-
The large intestine which ends with anus.
40- Digestion
takes place in three organs:
A- Mouth [Buccal digestion]
B-
Stomach [gastric digestion]
C- small intestine [intestinal
digestion ].
42-
There are two main types of glandular cells in the stomach:
HCl
creates an acidic medium which stop the action of ptyalin, activates
gastric enzymes as well as kills harmful bacteria.
B - Cells
secrete gastric enzymes (Pepsin).
43-
44-
Secretin hormone stimulates the pancreas to secrete sodium
bicarbonate also it activates the liver cells to secrete the bile.
45-
46-
47-
48-
49-
50-
Peptidases are a group of enzymes which catalyze the hydrolysis of
polypeptides into amino acids.
51-
52-
53-
54-
Absorption is the transfer of digested food to the blood and lymph by
diffusion or active transport.
55- The inner lining of
the ileum of the small intestine has tiny finger like projections
called villi, through them absorption happens.
56- The
absorbed food passes through two main routs:
A- fatty acids,
glycerol together with vitamins A, D, K pass through lymphatic route.
B - Water, mineral salts , glucose, amino acids together with
vitamin B, pass through blood route.
57- Wastes are
finally expelled out as feaces through the anus by means of strong
muscular contraction of the rectum together with the relaxation of
the anal sphincter.