AS Biology OCR Unit 1, Module 1 Cell Exchange and Transport- Cell Ultrastructure

 Unit 1, Module 1 Cell Exchange and Transport- Cell Ultrastructure information.

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Cell Ultrastructure
Magnification increases the size of an object
Resolution/resolving power ability to distinguish between adjacent points
Table 1-10-2: Microscopes (1)
Feature Optical microscope Electron microscope
Radiation Light Electrons
Magnification 400x (max1500) 500 000x
Resolution 2µm 1nm / 0,001µm
Electrons have a small
wavelength
\ Higher resolution
Vacuum in microscope Absent Present
Specimen is - Alive or dead - Dead (vacuum!)
- Stained
Transmission microscope:
Electrons pass through internal
structure of specimen
Scanning microscope:
Beams of electrons are reflected
off specimens surface. Allows a
three dimensional view
Cell wall (plant cells only)
Made up of cellulose fibres which provide strength
Cell does not burst if surrounding solutions become dilute
Nucleus (5µm)
Contains chromosomes (genes made of DNA which control cell activities)
Separated from the cytoplasm by a nuclear envelope
The envelope is made of a double membrane containing small holes
These small holes are called nuclear pores (100nm)
Nuclear pores allow the transport of proteins into the nucleus
Rough Endoplasmic Reticulum (rough ER)
Have ribosomes attached to the cytosolic side of their membrane

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Found in cells that are making proteins for export (enzymes, hormones, structural proteins,
antibodies)
Thus, involved in protein synthesis
Modifies proteins by the addition of carbohydrates, removal of signal sequences
Phospholipid synthesis and assembly of polypeptides
Smooth Endoplasmic Reticulum (smooth ER)
Have no ribosomes attached and often appear more tubular than the rough ER
Necessary for steroid synthesis, metabolism and detoxification, lipid synthesis
Numerous in the liver
Ribosomes (20-30nm)
Small organelles often attached to the ER but also found in the cytoplasm
Large (protein) and…read more

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Nutrients diffuse through lysosomal membrane into the cytosol
Mitochondria (1µm in diameter and 7µm in length)
Mostly protein, but also contains some lipid, DNA and RNA
Power house of the cell
o Energy is stored in high energy phosphate bonds of ATP
o Mitochondria convert energy from the breakdown of glucose into adenosine
triphosphate (ATP)
o Responsible for aerobic respiration
Metabolic activity of a cell is related to the number of cristae (larger surface area) and mitochondria
Cells with a high metabolic activity (e.g.…read more

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Nucleoli \ Absent \ Present
- Chromosomes (DNA) Single and circular Many and linear
Centriole (for mitosis) Absent Only in animal cells…read more

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