Cells and Microscopy

Question 1

Describe the Mitochondrion

Answer 1

Usually oval shaped, with a double membrane, with the inner folded to form “cristae”. Inside is the matrix, which contains enzymes in respiration.

Question 2

What is the function of the Mitochondrion?

Answer 2

It is the site of aerobic respiration, where ATP is released. They’re found in large numbers in cells that are active.

Question 3

Describe the golgi apparatus

Answer 3

A group of fluid-filled, membrane bound flattened sacs, stacked on top of one another.

Question 4

What is the function of the golgi apparatus?

Answer 4

It stores, modifies, and packages proteins and lipids. It also creates lysosomes.

Question 5

Describe the ribosome

Answer 5

A small organelle that floats freely in the cytoplasm or is attached to the Rough endoplasmic reticulum. It has a large subunit and a small subunit.

Question 6

What is the function of the ribosome?

Answer 6

It synthesises protein.

Question 7

Describe the golgi vesicles

Answer 7

A small fluid-filled sac in the cytoplasm, produced by the Golgi apparatus. Surrounded by a membrane.

Question 8

What is the function of the Golgi vesicles?

Answer 8

Stores lipids and proteins made by the Golgi apparatus and transports them out the cell

Question 9

Describe a lysosome

Answer 9

A single-membrane bound sac, with no internal structure, and is a type of Golgi vesicle.

Question 10

What is the function of the lysosome?

Answer 10

It contains digestive enzymes known as lysozymes, breaking down food, broken/damaged organelles, and foreign matter. They are absent from plant cells.

Question 11

Describe the vacuole

Answer 11

It is a membrane-bound organelle found in the cytoplasm, containing a solution of sugar and salts. The membrane is known as the tonoplast.

Question 12

What is the function of vacuole?

Answer 12

It maintains pressure within the cell, keeping it from wilting through turger pressure. Also involved in the isolation of unwanted chemicals.

Question 13

Describe the cell-membrane

Answer 13

It is found on the the surface of animal cells, and is made up of lipids and proteins.

Question 14

What is the function of cell membrane?

Answer 14

It regulates the movement of substances in and out of the cell, as it has receptor molecules, allowing it to respond to chemicals or hormones.

Question 15

Describe the Rough Endoplasmic Reticulum

Answer 15

A fluid enclosed in a membrane, appears similar to string, with ribosomes on the surface (hence rough)

Question 16

What is the function of the Rough Endoplasmic reticulum?

Answer 16

It synthesises and folds proteins, but is also responsible for synthesising new membranes growing in place by adding proteins and phospholipids.

Question 17

Describe the Smooth Endoplasmic Reticulum

Answer 17

A Fluid enclosed in a membrane, with a smooth surface, appearing similar to fingers.

Question 18

What is the function of the Smooth Endoplasmic Reticulum?

Answer 18

It metabolises and processes lipids and carbohydrates, whilst hormones are also synthesised.

Question 19

Describe the Nucleus

Answer 19

A very large organelle surrounded by a nuclear envelope with a double membrane. Contains a nucleolus, pores in the membrane, and chromatin.

Question 20

What is the function of the nucleus?

Answer 20

Controls the cells activity and contain DNA, with the pores allowing substances to move between the nucleus and cytoplasm.

Question 21

Describe the nucleolus

Answer 21

A dense, solid structure composed of crystalline protein and nucleic acid.

Question 22

What is the function of the nucleolus?

Answer 22

It synthesises ribosomes.

Question 23

Describe the chloroplast

Answer 23

It is a small and flattened structure surrounded by a double membrane, with thylakoid membranes inside, which stack up to form grana, which are linked together by lamallae. There is a thick fluid inside called stroma.

Question 24

What is the function of the chloroplast?

Answer 24

It is the site of photosynthesis

Question 25

Describe the cell wall

Answer 25

It is a rigid structure.

• In plants and algae it is made by the cellulose.
• In fungi it is made of chitin.
• In prokaryotes it is made of murein.

Question 26

What is the function of the cell wall?

Answer 26

It supports the cell and prevents it losing its shape, therefore making the plant keep its shape.

Question 27

What organelles are exclusively in Plants?

Answer 27

Cell wall, chloroplasts, plastids,and the large vacuole

Question 28

What organelles are exclusively in animals?

Answer 28

Lysosomes

Question 29

How does a eukaryotic nucleus differ from a prokaryotic nucleus?

Answer 29

The eukaryote has a membrane bound nucleus

Question 30

What does a prokaryotic cell have instead of a eukaryotic cell?

Answer 30

Mesosomes.

Question 31

What are the type categories of microscopes we use to study cells ?

Answer 31

Light/optical microscopes

Electron microscopes

Question 32

What are the advantages of light/optical microscopes?

Answer 32

• living cells can be observed
• Natural colour can be seen
• movement can be observed
• specimen are rarely distorted during preparation

Question 33

What are the disadvantages of light/optical microscopes ?

Answer 33

• limited magnification

- limited resolution which is limited by the wavelength of light (0.2micrometers)

Question 34

What are the advantages of scanning electron microscopes?

Answer 34

• High magnification of x500000
• High resolution (20nm)
• 3D image produced

Question 35

What are the disadvantages of scanning electron microscopes ?

Answer 35

• High energy electrons can destroy specimen
• preparation distorts specimen
• vacuum is needed, so no living cells
• all images are black and white
• cells become dehydrated
• expensive (over £1m)
• large and requires special rooms
• complex preparation

Question 36

What are the advantages of transmission electron microscopes?

Answer 36

• High magnification (x500000)

- High resolution (0.1nm)

Question 37

What are the disadvantages of transmission electron microscopes ?

Answer 37

• very thin preparations are needed
• High energy electrons can destroy specimen
• preparation distorts specimen
• vacuum is needed meaning there are no living cells
• all images are black and white
• cells are dehydrated
• expensive (over £1m)
• expensive to produce electron beam
• large and requires special room

Question 38

What is the equation for magnification?

Answer 38

Magnification = size of the image / size of the object

Question 39

What are ribosomes made up of?

Answer 39

Ribosomal RNA and protein

Question 40

What lens on a microscope is close to the microscope slide?

Answer 40

The objective lens

Question 41

What is resolution?

Answer 41

The minimum distance apart that two objects can be distinguished as separate objects in an image

Question 42

Describe how light/optical microscopes work?

Answer 42

Light microscopes use a pair of convex glass lenses to magnify an image

Question 43

What is magnification?

Answer 43

How many times bigger the image is when compared to an object

Question 44

Describe binary fission of prokaryotic cells

Answer 44

1) circular DNA replicates and both copies attach to the cell membrane
2) The cell membrane begins to form between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm
3) A new cell wall forms between the two DNA molecules dividing the original cell.

Question 45

Describe the process of cell fractionation.

Answer 45

1) The cells are first blended in a homogeniser forming a homogenate. This is then placed in a centrifuge and spun at a slow speed
2) The heaviest organelles are forced to the bottom of the tube forming a pellet
3) The fluid at the top (supernatant) is removed which leaves just the pellet. The supernatant is transferred to another tube and spun at a slightly faster speed, repeating the process.