[11.1] overview of photosynthesis Flashcards
1
Q
what is the purpose of a leaf’s adapations?
A
- to bring together the raw materials of photosynthesis: water, carbon dioxide and light
- to remove the products of pts: oxygen and glucose
2
Q
what are the leaf’s adapations?
A
- large SA to absorb as much sunlight as possible
- arrangement of leaves on plant that minimises overlapping so avoids the shadowing of one leaf by another
- thin, as most light is absorbed in first few micrometres of the leaf and diffusion distance for gases is kept short
- transparent cuticle and epidermic that let light through to the photosynthetic mesophyll cells beneath
- long, narrow upper mesophyll cells packed with chloroplasts that collect sunlight
- numerous stomata for gas exchange so all mesophyll cells are only a short diffusion pathway from one
- stomata that open and close in response to changes in light intensity
- many air spaces in lower mesophyll layer to allow rapid diffusion in the gas phase of carbon dioxide and oxygen
- a network of xylem that brings water to the leaf cells
- phloem that carries away the sugars produced during pts
3
Q
what are the 3 main stages of photosynthesis?
A
- capturing of light energy by chloroplast pigments such as chlorophyll
- light-dependent reaction
- light-independent reaction
4
Q
define wavelength
A
distance between a point on one wave and the same point on the next wave
5
Q
define frequency
A
number of waves produced by a source in each second
6
Q
how do chlorophyll molecules embed themselves in the PLB of the thylakoid membrane and why?
A
- at an angle so they can absorb more light
- chain sits on thylakoid membrane
- head remains on surface of membrane
7
Q
describe the structure of chlorophyll
A
- head is porphyrin ring, similar to haemoglobin
- contains Mg²⁺ in the head
8
Q
what is the purpose of photosynthetic pigments?
A
to absorb and capture light eneter
9
Q
what are the 5 main photosynthetic pigment?
A
- chlorophyll a (blue-green pigment)
- chlorophyll b (yellow-green pigment)
- carotenoids: xanthophyll (yellow) and carotene (orange)
- phaetophytin (grey pigment)
10
Q
why are the pigments coloured?
A
- because they absorb particular wavelengths of light and reflect others
- proportions of other pigments account for varying shades of green found between species of plants
11
Q
what regions of the colour spectrum do chlorophylls and carotenoids absorb?
A
- chlorophylls: red and blue-violet
- carotenoids: blue-violet
12
Q
describe engelmann’s experiment
A
- placed algae on petri dishes and shone light onto it but through a prism
- this dispersed the light onto different wavelengths
- initially, the aerotactic bacteria was randomly dispersed by then became concentrated at the blue and red ends of the spectrim, less at green / yellow
12
Q
what is an action spectrum?
A
- the rate of physiological activity plotted against wavelength of light
- shows which wavelength of light is most effectively used in a specific chemical reaction
