Unit 3 Biology IGCSE O level

PLANTS AND FOODS

Staple die

They all contain starch, which is the main storage of carbohydrate made by plants

Starch

which is a good way of storing carbohydrate because it is insoluble, compact and can broken down easily

Testing level for starch

1.a beaker of water is set up on a tripod and gauze and the water is heated until it boils

2.a leaf is removed from the [plant and killed by placing into the boiling water(for 30 seconds)

3.then the leaf is placed in a boiling tube containing ethanol, and tube is placed into a beaker of hot water to remove most of the chlorophyll from the leaf

4.when the leaf is turned colorless or pale yellow, removed and washed with cold water

5.then spread out on the tile and covered the iodine solution

6.the leaf contain starch will turn dark blue black color means which has plenty of starch

what is starch?

It is only made in the parts of the chlorophyll.. It is composed of long chains of glucose

Three important facts about starch production by leaves

• it uses carbon dioxide from the air

• it needs light

• it needs chlorophyll in the leaves

Oxygen

which is essential to the existence of the most living thing on earth

Does the plants made starch directly?

No, but it starts produces glucose, which is then joined together in chains to form starch molecules

Carbohydrate

which is made of many sugar sub-units is called polysaccharide

Photosynthesis

Plants use the simple organic molecules carbon dioxide and water in the presence of chlorophyll and light, to make glucose and oxygen(which also convert light energy into chemical)

Th role of green pigment, chlorophyll

to absorb light energy needed for the the photosynthesis to take place

Respiration

which is carried out by both animals and plants, release energy(but not light) from the breakdown of glucose

other need facts for photosynthesis

• leaves need to be large surface area to absorb light, many chloroplasts contain many chlorophyll

• need to release oxygen and water vapor from the leaf cell

leaf stalk

which can grow to allow the blade of the leaf to be angled to receive the maximum amount of sunlight

the two outer layer of cells

1.upper epidermis

2.lower epidermis

the two outer layer

which have few chloroplasts and covered by thin layer of a waxy material called the cuticle

cuticle

reduces the water loss by evaporation, and acts as a barrier to the entry of disease-causing microorganisms such as bacteria or fungi

the lower epidermis

which has many holes or pores called stomata

upper epidermis

contains few or no stomata

Stomata

• allow carbon dioxide to diffuse into the leaves to reach the photosynthesis tissues

• also allow oxygen and water vapor to diffuse out

the stomata formed

as a gap between two highly specialised cell called guard cell, which can change their shape to open or close the stomata

mesophyll

• located in the middle of the leaf are two layer of photosynthesis

Palisade mesophyll

below the upper epidermis, this is a tissue of long, narrow cell each containing thousand of chloroplasts, it is the main site of photosynthesis

where is the palisade mesophyll cell locate?

They are close to the source of light, and upper epidermis is relatively transparent, allowing the light to pass through to the enormous number of chloroplast which lie below

Spongy mesophyll

Spongy Mesophyll

below the palisade layer is a tissue mase of more rounded , loosely packed cells, with air space between them. They also form photosynthesis, but have fewer chloroplasts than the palisade cell

Function of spongy mesophyll

the main gas exchange surface of the leaf, absorbing the carbon dioxide and releasing oxygen and water vapour.(the air space allow these gases to diffuse in and out of the leaf)

Xylem

Water and mineral ions are supplied to the leaf by vessels in a tissue

Function of xylem

forms a continuous transport system through out the plant. Water is absorbed by the root and passes up through the stem and through veins in the leaves in the transpiration steam

phloem

The products of photosynthesis, such as sugar are carried away from the mesophyll cells by another transport system

Function of phloem

supplies all other parts of the plant, so that tissues and organ that can’t make their own food receive products of photosynthesis

veins

which contains both xylem and phloem tissue, and branch again and again to supply all other parts of the leaf

Effect of photosynthesis

plants supply animals with two of their essential need, food and oxygen, (as well as removing carbon dioxide from the air

function of living cells

including plant cells, respire all the time and they need oxygen for this. When the light intensity is high, a plant carries out photosynthesis at a much higher rate than it respires.

factor effecting rate of photosynthesis

1.light intensity

2.carbon dioxide concentration

3.temperature

glucose

it is a single sugar unit (a monosaccharide)

monosaccharide

also known as fructose which is found in fruit

disaccharide sucrose

which is the main sugar carries in the phloem.

polysaccharide

disaccharide can also changed into another polymer, the polysaccharide is called cellulose, which form plant cell walls

carbohydrate

all of the sugar unit are carbohydrate. plant cell can also convert into lipids(fats and oil)

function of lipids

they are needed for the membrane of all cells , and are also an energy store in many seeds and fruits, such as peanuts, sunflower seeds and olives

carbohydrate and lipids both contain

only three elements ,carbon, hydrogen and oxygen

nitrate ions

which are absorbed from the soil water, along with other minerals such as phosphate, potassium and magnesium ions

Phosphate

needed for the plants cells to make many important compounds, including DNA

Potassium ions

they are required for the enzymes in respiration and photosynthesis to work, and magnesium forms a part of the chlorophyll molecule

uses of nitrate

making amino acids, proteins, chlorophyll, DNA and many other compounds

Deficiency symptoms for deficiency of nitrate

limited growth of plants ,older leaf turn yellow

uses of phosphate

making DNA and many other compounds; part of the cell membrane

deficiency symptoms for deficiency of phosphate

poor root growth : younger leaves turn purple

uses of potassium

need for enzymes of respiration and photosynthesis to work

deficiency symptoms for potassium

leaves turn yellow with dead spot

uses of magnesium

part of chlorophyll molecules

deficiency symptoms for magnesium

leaves turn yellow

omosis

is the name of the process by which water move into and out of the cell

where is the osmosis happen?

happen when the material called partially permeable membrane separates two solution

Visking tubing

is a artificial partially permeable membrane and it is also use in kidney dialysis machines

function of Visking tubing

has microscopic holes in it, which let small molecules like water pass through but is not permeable to some larger molecules, such as the sugar sucrose

osmosis in other word

there is a greater diffusion of water molecules from the more dilute solution to the more concentrated solution

water potential

how ‘free’ the water molecules are to move

osmosis in cells

the cell surface membrane of both animal and plant cell are partially permeable so is the inner membrane around the cell’s sap vacuole

structure of the plant cell

around the plant cell is the tough cellulose cell wall which keep the shape of the cell and can resist change of the pressure inside the cell

sap vacuole

contain many dissolved solutes, such as sugars and ions

function of osmosis in plants cell

if the plant cell is put into the water or dilute solution , the content of the cell have low water potential than external solution ,so the the cell will absorb water by osmosis

turgid

the cell then swells up and the cytoplasm pushes against the cell wall .A plant cell that has develop an internal pressure like this

flaccid

the cell decrease in volume and the cytoplasm no longer pushes against the cell wall

Plasmolysed

the cell contents shrink so much that the membrane and cytoplasm split away from the cell wall and gaps appear between the wall and the membrane

turgor(the statement a plant is in when its cells are turgid)

is very important to plants

function of tiny roots hair

the regions just behind the growing tips of the roots of a plant are covered in thousand of tiny roots hairs

tiny roots hair

they are the main sites of water absorption by the roots, where the hair greatly increase the surface area of the root epidermis

transpiration

the losses of water vapour from the leaves

transpiration steam

causes the water to be pulled up the xylem in the stem and roots in a continuous flow

transpiration stem has more than one important function

1. supplies water for the leaf cells to carry out photosynthesis

2. carries mineral ions dissolved in the water

3. provides water to keep the plant cells turgid

4. allow evaporation from the leaf surface , which cools the leaf , in a similar way to sweat cooling the human skin