B4.4 Biogenetics


Subcellular structure of a plant cell:

cytopasm- where the reactions happen

ribosomes- ribosomes make protein. protein is needed for many cell functions such as repairing damage or directing chemical processes.

cell membrane- controls what goes in and out 

cell wall- supports the cell

chloroplasts- where photosynthesis happens 

mitochondria- where respiration happens 

vacuole- stores cell sap - keeps the cell ridgid 

nucleus- controls the cell - stores genetic information


Image result for symbol equation for photosynthesis (http://4.bp.blogspot.com/-Yo0kkS3BY-w/Vk1kAowUvQI/AAAAAAAAAho/6uPL6fZUqPc/s1600/photosynthesisequation.gif)

Parts of a plant:

stem = carrys nutrients and water from the roots + holds the plant up

roots = absorbs water and nutrients

leaves = photosynthesis

flower = attracts insects for reproduction and pollenation

Tissues in the cross section of a leaf:

Image result for cross section of a leaf (http://www.funsci.com/fun3_en/guide/guide4/micro4_en_39.gif)

lower epidermis- covers the lower surface and protects them 

upper epidermis- covers the surface and protects them 

palisade mesophyll- contains lots of chloroplasts to carry out photosynthesis 

spongy mesophyll- contains some chloroplasts, but also has big air spaces and a large surface area to make diffusion of gases easier 

xylem and phloem- transport tissues, xylem carries water and dissolved mineral ions from roots up to the leaves, phloem carries dissolved food from leaves around the plants. 

stomata-takes in carbon dioxide and releases oxygen Image result for stomataguard cells open and close .

Hierachy of organisms: 

cells --> tissues ---> organ ---> organ system --> organism 


1. converted into insoluble starch for storage 

2.used to produce amino acids for protein synthesis 

3. used to produce fats and oils for storage 

4. used to produce cellulose to strengthen the cell wall

5. used for respiration for the plant 


1. large surface area- more sunlight absorbed for photosynthesis 

2. thin- chloroplasts are more accessible to the sun

3. veins (xylem and phloem)- a transport system to move food and water 

4. lots of chloroplasts- lots of photosynthesis

5.air spaces within the leaf- to allow easy gas exchange 


Cells in algae and plants are full of sub-cellular structures called chloroplasts, they contain a green substance called chlorophyll which makes the leaf green.

During photosynthesis the energy is transferred from the environment to the chloroplasts by light.


 Image result for photosynthesis plant

word equation: carbon dioxide + water --> glucose + oxygen 

symbol equation: 6Co2 + 6H2O = C6H12O6 + 6O2


Image result for endothermic reactions plant


  • oxygen is mainly released into the air which we then use for respiration
  • each year plants produce approximately 368000000000 tonnes of oxygen. 

Required Practical : Investigating the effect of a factor on the RATE of photosynthesis using an aquatic organism such as pondweed.

 rate- how much reactant is used or how much product we get in a certain period of time

Conclusion- we found that the further away the light was from the pondweed,


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