Overview of Photosynthesis Flashcards Preview

A- Level Biology - Photosynthesis > Overview of Photosynthesis > Flashcards

Flashcards in Overview of Photosynthesis Deck (35)
Loading flashcards...

Why is photosynthesis so important to us as humans?

They produce the oxygen we breathe by releasing it from the water molecules

Photoautotrophic organisms carry out photosynthesis

Light energy is absorbed by chlorophyll and converted into chemical energy

Biological molecules stored in plants and algae may be consumed by hetertrophs


What does life depend on?

Continous transfers of energy


What does this energy that eneters the organism depend on?

The type of nutrition

In plants, energy in light is absorbed by chlorophyll and then transferred into chemical energy of the molecules formed during photosynthesis. These molecules are used by the plant to produce ATP during respiration

Non-photosynthetic organisms feed on the molecules produced by plants and then use them to make ATP during respiration


Where is the site of photosynthesis?

Leaf is the main photosynthetic structure in the eukaryotic plants

Chloroplasts are the cellular organelles within the leaf where photosynthesis takes place


Why are leaves adapted to bring and remove waste products?

  • Leave bring: (Raw materials of photosynthesis
    • Water
    • Carbon dioxide
    • Light
  • Leaves remove its products
    • Oxygen
    • Glucose


Why is it important that leaves have a large surface area?

  • Absorbs as much sunlight as possible


Why is it important with the arrangement of leaves on a plant?

  • Minimises overlapping and avoids the shadowing of one leaf by another


Why is it important that leaves are thin?

  • As most light is absorbed in the first few micrometres of the leaf 
  • Keeps the diffusion distance for gases short


Why is it important a leaf has a transparent cuticle and an epidermis?

Let the light through to the photosynthetic mesophyll cells beneath


Why is it important that leaf has long, narrow upper mesophyll cells packed with chloroplasts?

They can collect sunlight


Why is it important that the leaves have numerous amount of stomata for gas exchange?

  • So that all mesophyll cells are only a short diffusion pathway from one


What do stomata open and close to?

In response to changes of light intensity


Why do leaves have many air spaces in the lower mesophyll layer?

Allow rapid diffusion in the gas phase of carbon dioxide and oxygen


Why do leaves have a network of xylem and phloem?

Brings water to the leaf cells - xylem

carries away the sugars produced during photosynthesis - phloem


What is the chemical equation of photosynthesis?


6CO2 + 6H2O -> (light) C6H12O6 + 6O2


What is the word equation for photosynthesis?

carbon dioxide + water -> glucose + oxygen


What is the problem with the chemical/word equation for photosynthesis?

It is oversimplified 

photosynthesis is a complex metabolic pathway involving many immediate reactions

it is a process of energy transferral in which some of the energy in light is conserved  in the form of chemical bonds.


Three main stages of photosynthesis simplified 

Stage 1 - capturing of light energy

Capturing of light energy by chloroplasts pigments such as chlorophyll


The three main stages of photosynthesis simplified 

Stage 2 - the light-dependent reaction

the light-dependent reaction in which some of the light energy is absorbed is converted into chemical bonds.

During this process, electron flow is created by the effect of light on the chlorophyll, causing water to spilt (photolysis) into protons and electrons, and oxygen.

The products are reduced NADP, ATP and oxygen 


The three main stages of photosynthesis simplified 

Stage 3 - the light-independent reaction

the light-independent reaction in which these protons (hydrogen ions) are used to produce sugars and other organic molecules


Where does photosynthesis occur in eukaryotic plant cells organelles?



What typically size is chloroplasts?

2 - 10 µm

However sometimes vary in shape and size

(usually disc shaped)


Do chloroplasts have a double membrane?



Structure of grana

There are stacks of 100 disc-like structures called thylakoids 

this is where the light-dependent reaction of photosynthesis takes place.

Within the thylakoids is a photosynthetic pigment called chlorophyll

Some thylakoids have tubualr extensions that join up with thylkaloids in thr adjacent grana. These are called intergranular lamellae 


Structure of stroma


  • It is a fluid-filled matrix where the light-independent stage of photosynthesis takes place
  • Within the stroma are a number of other structures such as starch grains



Diagram of chloroplast


What is granum?

A stack of thylakoid discs


What is plural of granum?

Grana (more than one stack)


How does water move through plant?

They use the xylem - cohesion tension theory

Adhesion - attracted to the interior of the capillary

Cohesion - between the water molecules

Tension - pull through the transpiration stream


Where do algae and plants carry most of their photosynthesis from?

In the ocean