Food tech week 1 skills training

2. Give two examples of specific fluorescent molecules that can be used to visualize the location of specific compounds in cells. Also include how this process works at the molecular level.

Reader: practical 1, skills training

Various molecules emit light of a certain wavelength after they are excited with light of a shorter wavelength; this phenomenon is referred to as fluorescence.

Some of these fluorescent molecules may also bind specifically to certain compounds in the cell and these molecules make potential fluorescent dyes.

Examples are:

• DAPI which binds to DNA and flurosces as blue

• GFP is a green fluroscent protein which is used to visualize the localization of proteins in time-lapse imaging of living cells.

• Because fluorescent dyes emit light, objects even smaller than 0.2 µm can be observed.

   

Describe the ultrastructure of the nucleus, including differences in degree of DNA packaging, and describe the function of the nucleolus.

• nucleus is surrounded by a double membrane which is the nuclear envelope

• it isolates the content of the nucleus from the cellular cytoplasm

• nuclear pores in the envelope allow selective transport of molecules in and out of the nucleus

• the nuclear lamina provides mechanical support to the nucleus

• the nucleus contains a highly viscious fluid called the nucleoplasm, which contains genetic material , organized as multiple long DNA strands wound around a variety of proteins

• The DNA and these proteins together is called chromatin

• the degree of condensation influences the DNA’s accesibility to polymerases and thereby rate of transcription

• The most highly condensed form of interphase chromatin is called heterochromatin

• loosely packed DNA which may be transcriptionally active is called euchromatin

• the content of the nucleus is not uniform

• the nucleolus is the site of ribosome biogenesis

• the nucleolus contains the genes that code for rRNA

5. Describe the function of several types of plastids (amyloplast, chloro-amyloplast, chloroplast, chromoplast) and mention the three membranes of chloroplasts and their organization

• a plastid is a membrane bound organelle which is found in plant and algal cells where it is the site of manufacturing or storage of important chemical compounds.

• amyloplasts and chromoplasts are the location of the storage and synthesis of starch and pigments

• chloroplasts is also a plastid and it is a site of photosynthesis

• chloroplasts have an outer chloroplast membrane and an inner chloroplast membrane around the stroma

• chloroplasts also contain the thylakoid membrane→ a highly folded membrane system which contains the chlorophyll pigment

• stacks of the thylakoid region is the grana

• these grana are all connected the connecting membrane regions are called stroma-thylakoids

• chloroplasts can transform into chloroamyloplasts(plastids which contain both chlorophyll and starch)

dimensions of chloroplast

3-10micrometer in diamter

Explain why mitochondria and chloroplasts are thought to have been evolved from free-living bacteria that were engulfed by eukaryotic cells.

• both contain their own DNA and ribosomes

• both contain circular DNA like bacteria instead of the linear DNA found in the nucleus of eukayotes

• the ribosomes are similar to those found in bacteria not in the cytoplasm of eukaryotes

• both organelles reproduce by binary fission(again like bacteria)

• they also have the same size as proakaryotic cells

• both have a double membrane both having bacterial origin a third membrane derived from the plasma membrane during engulfment dissapered