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Year 12 Biology > Microscopes and cell structure > Flashcards

Microscopes and cell structure Flashcards

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1
Q

Define magnification

A

The number of times larger an image appears compared to the original object

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2
Q

Define resolution

A

The ability of an optical instrument to distinguish between two points that are close together on an object

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3
Q

Optical microscopes allow a magnification of up to?

A

1500 x

In some cases 2000 x

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4
Q

Give an example of an organelle a light microscope cannot magnify?

A

Ribosomes as they have a diameter of 20nm

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5
Q

What is a laser scanning/ confocal microscope?

A

Lasers scan the surface of an object and display it on a computer screen

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6
Q

What are the features of a laser scanning/ confocal microscope?

A

Can focus on structures at different depths within cells

Can observe live organisms

Show high contrast and high resolution

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7
Q

What are the types of electron microscope and what electron micrographs do they form?

A

Transmission electron microscope - forms a 2D, black and white image.

Scanning electron microscope - electrons bounce off the surface of the object, forms a 3D, black and white image.

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8
Q

Explain the similarities between a scanning and a transmission electron microscope.

A

Organisms have to be dead

The specimen is chemically fixed and stained with metal salts

Organism has to be in a vacuum

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9
Q

Explain the differences between a transmission and a scanning electron microscope

A

Transmission - is a 2D, black and white image.

Scanning - is a 3D image, where colour can be digitally added

Transmission - magnifies up to 50 million times

Scanning - magnifies up to 20 000 times

Transmission - electrons pass through the specimen

Scanning - electrons ‘bounce’ of the surface

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10
Q

What stain is commonly used on specimens?

A

Methylene blue

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11
Q

Why do we stain specimens?

A

To differentiate between structures

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12
Q

What does Sudan Red stain?

A

Lipids

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13
Q

What does Iodine stain?

A

Cellulose

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14
Q

What stains chromosomes?

A

Acetic Orcein

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15
Q

What are the limitations of observing structures under microscopes?

A

Cells are 3D and most photomicrographs show 2D sections

Not all structures are visible depending on where you cut

Structures may appear as different shapes depending on their orientation.

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16
Q

Describe the structure of the nucleus

A

Double membrane called the nuclear envelope

Has nuclear pores

Nucleolus containing RNA

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17
Q

Describe the function of the nucleus

A

Envelope separates contents

Pores allow larger substances like mRNA through

Nucleolus produces ribosomes

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18
Q

Describe the structure of the Rough Endoplasmic Reticulum (RER)

A

A system of membranes containing fluid filled cavities
(cisternae)

Coated in ribosomes

19
Q

Describe the function of the RER

A

Cisternae provided channels to transport substances

Provides a large surface area for ribosomes

Assembles amino acids into proteins

20
Q

Describe the structure of the Smooth Endosplasmic Reticulum

A

Same as the RER, but no ribosomes on surface

21
Q

Describe the function of the SER

A

Contains enzymes to catalyse reactions involved with lipid metabolism

22
Q

Describe the structure of the Golgi Apparatus

A

Stacks of membrane bound, flattened sacs

Secretory vessels bring substances to and from the Golgi

23
Q

Describe the function of the Golgi Apparatus

A

Modifies proteins:

Can add sugar and lipid molecules to make glycoproteins and lipoproteins

Folds proteins into their 3D shape

Packages proteins into vesicles

24
Q

Describe the structure of the mitochondria

A

Double membrane

Inner folded membrane called the Cristae

Fluid filled matrix within

25
Q

Describe the function of mitochondria

A

Site of ATP production

Abundant where metabolic activity is high

26
Q

Describe the structure of the chloroplasts

A

Double membrane

Thylakoids are flattened sacs, containing chlorophyll

Each stack is a granum

Stroma (fluid)

Loops of DNA and starch grains

27
Q

Describe the function of the chloroplasts

A

Site of photosynthesis

Abundant in palisade cells

( 1st stage of photosynthesis - Light energy trapped bay chlorophyll to make ATP, in the grana)

(2nd stage of photosynthesis - hydrogen reduced to co2, to make carbs, in the stroma)

28
Q

Describe the structure of the vacuole

A

Tonoplast membrane contains fluid

29
Q

Describe the function of the vacuole

A

Filled with water and solutes to maintain cell turgidity

30
Q

Describe the structure of the lysosome

A

Small ‘bags’ formed in the Golgi

Contain powerful hydrolytic enzymes

31
Q

Describe the function of the lysosome

A

Separate enzymes from then rest of the cell

Engulf old organelles and foreign/ dead matter

32
Q

Describe the structure of the cilia and undulipodia

A

Protrusions from the cell surrounded by the cell surface membrane

Formed from centrioles and contain microtubules

33
Q

Describe the structure of ribosomes

A

Small and spherical

Made of RNA

Made in the nucleolus

34
Q

Describe the function of ribosomes

A

Synthesise proteins to be exported out of the cell

35
Q

Describe the structure of centrioles

A

Two bundles of microtubules at right angles

Arranged to form a cyllinder

36
Q

Describe the function of centrioles

A

Threads of tubular extend from the centriole during mitosis

37
Q

Describe the structure of the cytoskeleton

A

Network of protein structures

Rods of microfilaments made from actin

Myosins, as well as other proteins, act as motors

38
Q

Describe the function of the cytoskeleton

A

Support and mechanical strength

Allow cell movement

Form the track for motor proteins

Intermediate filaments anchor the nucleus in place

39
Q

Describe the 1st half of the secretion of a protein (up until the RER)

A

A gene is transcribed onto mRNA

mRNA passes out through the nuclear pore

At the RER, instructions are translated in the ribosomes and proteins are made

Molecules pass through the cisternae

40
Q

Describe the second half of the secretion of a protein

A

Vesicles leave the RER to the Golgi, via microtubules

Vesicles fuse with the Golgi where the protein is modified

Molecules pinch off the Golgi and are transported again to the plasma membrane

Vesicle fuses with the plasma membrane and exocytosis occurs

41
Q

How are prokaryotic and eukaryotic cells similar?

A

Both have a plasma membrane, cytoplasm, ribosomes, DNA and RNA

42
Q

How are prokaryotic cells different from eukaryotic cells?

A

Naked DNA is wrapped around histone proteins

No nucleus

Much smaller

Peptidoglcan wall

No membrane bound organelles

43
Q

What are some additional features of a prokaryotic cell?

A

Pili

Flagella

Waxy capsule

44
Q

What evidence is there that eukaryotic cells, like mitochondria, have evolved from prokaryotic cells?

A

The endosymbiont theory - both divide by binary fission, have plasmid DNA’s and have small ribosomes

Year 12 Biology (3 decks)

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