ultrastructure of cells

Question 1

2 types of microscope

Answer 1

• optical & electron

Question 2

optical microscopy (light)

Answer 2

• specimens are illuminated , uses stain to see structure

Question 3

electron (scanning)

Answer 3

• texture and surface detail

Question 4

optical vs electron

Answer 4

• o- coloured (lower levels, living cells)

- e- b&w

Question 5

eukaryotic cells

Answer 5

• Plant and animal cells are characterised by the presence of a number of cell organelles enclosed in membranes.
• The membrane bound organelles found in plant and animal cells include the nucleus, mitochondria, endoplasmic reticulum, Golgi complex and lysosomes.

Question 6

cytosol

Answer 6

• The cell organelles in plant and animal cells are located
  within a fluid region of the cell called the cytosol.
• The cell organelles (minus nucleus) + the cytosol =
  cytoplasm

Question 7

plant cell

Answer 7

• Plant and animal cells are slightly different.
• Plant cells have membrane bound organelles called
  chloroplasts.
• Plant cells have a large central vacuole bound by a
  membrane.
• Takes up 80-90% of cell volume

Question 8

vacuoles

Answer 8

• Plant vacuoles are fluid filled and separated from the rest of the cytosol by a membrane called the tonoplast. It controls the entry and exit of substances.
• Vacuoles store nutrients and mineral salts, are and involved in waste disposal.

Question 9

cell wall

Answer 9

• Cell walls are found in plant, algae, fungi and some
  prokaryotic cells.
• They are not present in animal cells

Question 10

cell walls pt2

Answer 10

• Cell walls are located outside the plasma membrane.
• It provides strength and support to cells, and prevents the cell from ‘bursting’ if too much water enters the cell via osmosis.
• Cell walls can be made up of a range of compounds.

Question 11

plant cell wall

Answer 11

• Primary cell wall in plants is made of cellulose combined with other substance.
• The primary cell wall provides the strength

Question 12

nucleus

Answer 12

• The nucleus controls the functions of plants, animals and fungi cells.
• It is the defining feature of eukaryotes.
• It is enclosed in a double membrane known as a nuclear envelope.

Question 13

nucleus pt2

Answer 13

The functions of the nucleus include:

• Control of DNA replication
• Repair of genetic material
• Initiation of gene expression
• Control of metabolic activities (regulates genes)
• The nucleus contains the DNA of the cell.
• There are structures called nucleoli inside the nucleus that produces rRNA (rRNA taught at a later time)

Question 14

mitochondria

Answer 14

• Cells use energy in the form of adenosine triphosphate
  (ATP)
• Mitochondria produce ATP
• Mitochondria are not present in prokaryotic cells

Question 15

ribosomes

Answer 15

• Ribosomes are the site in the cell where proteins are made.
• Amino acids are assembled and joined into polypeptide chains or proteins.
• There are large numbers of ribosomes in a cell

Question 16

ribosomes pt2

Answer 16

• There are many ribosomes attached to membrane
  channels known as the endoplasmic reticulum (ER).
• Proteins made on the ER are generally exported from the cell
• Other ribosomes are ‘floating’ in the cytosol

Question 17

endoplasmic reticulum

Answer 17

• The ER is an interconnected system of membrane-enclosed channels.
• If there are ribosomes attached, it is known as rough ER
• If there are no ribosomes attached, it is known as smooth ER

Question 18

rough ER

Answer 18

• Involved in transporting proteins to sites within cell

- Processing proteins prior to transport

Question 19

smooth ER

Answer 19

• Involved in manufacture of substances e.g. lipids
• Detoxifying harmful products
• Storage and release of substances

Question 20

golgi complex

Answer 20

• Responsible for the export of substances out of cells (e.g. proteins)
• Is a multilayered structure composed of stacks of
  membrane-lined channels

Question 21

lysosomes

Answer 21

• Lysosomes are fluid filled sacs of digestive enzymes

- Found in animal cells, similar organelle found in plant cells (‘lysosome-like vacuoles)

Question 22

lysosomes pt2

Answer 22

• Digest excess macromolecules (e.g. proteins into
  smaller, useable units)
• Breakdown of non-functioning cell organelles (old or
  damaged)
• Breakdown of foreign substances (e.g bacteria)

Question 23

peroxisomes

Answer 23

• Small organelle found in cytoplasm of plant and animal
  cells
  -Contain a large number of enzymes
• Important in cellular metabolism and breakdown of toxic substances

Question 24

chloroplast

Answer 24

• Found in algae and plants
• Convert sunlight energy to chemical energy through a
  process called photosynthesis

Question 25

chloroplast pt2

Answer 25

• They are filled with light trapping pigments called
  chlorophylls. These give plants their green colour.
• Found in parts of plant cells that are exposed to sunlight