2. Germination & Enzymes
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Do Now in your OneNote/Notebook:
Write down the things you think a seed absolutely needs to start growing.
Do Now in your OneNote/Notebook:
Write down where plants get WOW from.
What is germination?
GERMINATION is the life process in which a seed changes from being dormant to actively growing.
Before a seed germinates, it is called dormant. Dormant is not dead, it is not growing either.
When a seed is in the right conditions, chemical reactions will start happening inside the seed - the seed will stop being dormant.
The PLUMULE and RADICLE will start to develop. The energy in the COTYLEDON will start to be used to make this happen.
These chemical reactions are called germination!
What happens during germination?
Step 1: Water enters the micropyle, so the seed absorbs water and swells. This breaks the testa.
Step 2: The radicle grows using the energy inside the seed. It grows downwards to hold the plant in the ground and absorb water from the soil.
Step 3: The seed uses energy to grow the plumule which comes out of the seed and grows upwards. It is trying to get sunlight so the new plant can do PHOTOSYNTHESIS.
Germination is finished when the plant has used up all the energy inside the seed and the plant begins to do photosynthesis.
Seeds need WOW to germinate - Water, Oxygen, Warmth!
To germinate, all seeds need:
Water - needed for the chemical reactions of germination, because the chemical reactions can only take place in solution when molecules are free to move.
Oxygen - needed for the seed to carry out aerobic cellular respiration. Respiration releases energy from GLUCOSE in the cotyledon, allowing the seed to grow the radicle and plumule.
Warmth - to speed up the chemical reactions of germination. These chemical reactions depend on ENZYMES, which only work in warm conditions.
Enzymes & Temperature
What is an Enzyme?
An enzyme is a type of protein that has a specific size and shape.
Each enzyme can only carry out one job. Some enzymes break big molecules into small molecules and some enzymes join small molecules together to make big molecules. Enzymes are NOT multifunctional.
Each enzyme has its own unique shape that whatever it is going to break apart or join together fits into.
What do enzymes do to make seeds germinate?
To make a seed germinate it needs GLUCOSE. The cotyledon is made of STARCH, which is lots of glucose joined together.
An enzyme called AMYLASE breaks apart the starch to release glucose. This glucose is then used during respiration and energy is released. The energy is used to grow the radicle and plumule.
The chemical reactions that take place during the process of germination are controlled by enzymes.
Germination, Warmth and Enzymes:
Enzymes have a temperature at which they work best at. More chemical reactions will take place at this temperature. That means more seeds will germinate at this temperature.
At low temperatures the enzymes work very slowly. The force of the collision between substrate and enzyme is to low/slow. The chemical reactions of germination will take place, but too slowly for germination to be successful.
High temperatures cause the ACTIVE SITE in the enzyme to change shape. This means there will be no working enzymes to control the chemical reactions of germination. Germination will not happen.