The Structure Of Chloroplasts

Question 0

Describe the pigment chlorophyll a

Answer 0

• p680 - photosystem 2
• p700 - photosystem 1
• each absorbs red light at a slightly different absorption peak
• both are found at the centre of photosystems and are known as the primary pigment reaction centre
• chlorophyll a also absorbs blue light of wavelength 450nm

Question 1

What are photosynthetic pigments?

Answer 1

• molecules that absorb light energy
• each pigment absorbs a range of wavelengths in the visible region and had its own distinct peak of absorption
• other wavelengths are reflected

Question 2

Describe the accessory pigments

Answer 2

• they absorb light wavelengths that are not well absorbed by chlorophyll sand pass the energy associate as with that light to the chlorophyll a at the base of the photosystem
• chlorophyll b –> absorbs light of wavelengths 500nm-640m and appears blue-green
• carotenoids –> reflect yellow and orange light and absorb blue light
- carotene (orange)
- xanthophyll (yellow)

Question 3

Describe how chloroplasts are adapted for their role

Answer 3

• inner membrane with transport proteins
–> controls entry and exit of substances between cytoplasm and stroma
• many grana
–> provide a large surface area
• photosynthetic pigments
–> arranged into special structures called photosystems which allow maximum light energy absorption
• proteins embedded in grana
–> hold photosystems in place
• fluid-filled stroma
–> contains enzymes needs to catalase the reactions of the light independent stage
• grana surrounded by stroma
–> products of the light-dependent reaction can easily pass into stroma
• chloroplast DNA and ribosomes
–> assemble and make the proteins