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cell structure Flashcards

1
Q

Define magnification

A

how many times larger the image is than the actual size of the object

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2
Q

Define resolution

A

The ability to see individual objects as separate entities

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3
Q

how to prepare dry mount

A

“Sectioning- Specimen is viewed whole or cut into very thin slices with a sharp blade.
Then the specimen is placed on the centre of the slide and a cover slip is placed over the sample”

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4
Q

how to prepare wet mount

A

Specimens are suspended in a liquid such as water or immersion oil. A cover slip is placed on from an angle

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5
Q

how to prepare squash slide

A

A wet mount is prepared first then a lens tissue is used to gently press down the cover slip. Damage can be avoided by squashing the sample between two microscope slides

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6
Q

how to prepare smear slide

A

The edge of a slide is used to smear the sample, creating a thin, even coating on another slide. A cover slip is then place over the sample.

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7
Q

why is staining used in microscopic

A

Staining is used to increase contrast in a specimen, in order to observe transparent and colourless structures.

to see certain names organelles

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8
Q

what is differential staining

A

Stains work by binding to different types of molecules or cell structures. This allows different components of cells to be identified, and is known as differential staining

can distinguish between two types of organism that would otherwise be hard to identify
can also differentiate between different organelles of a single organism

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9
Q

how do transmission electron microscopes work

A

“TEMs use electromagnets to focus a beam of electrons
This beam of electrons is transmitted through the specimen
Denser parts of the specimen absorb more electrons”

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10
Q

advantages of TEMs

A

“They give high-resolution images (more detail)

This allows the internal structures within cells (or even within organelles) to be seen”

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11
Q

disadvantages of TEMs (6)

A

“They can only be used with very thin specimens or thin sections of the object being observed
They cannot be used to observe live specimens (as there is a vacuum inside a TEM, all the water must be removed from the specimen and so living cells cannot be observed, meaning that specimens must be dead, unlike optical microscopes that can be used to observe live specimens)
The lengthy treatment required to prepare specimens means that artefacts can be introduced (artefacts look like real structures but are actually the results of preserving and staining)
They do not produce a colour image (unlike optical microscopes that produce a colour image)
Expensive to buy and operate
Large and unportable
“

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12
Q

how do SEMs work

A

“SEMs scan a beam of electrons across the specimen

This beam bounces off the surface of the specimen and the electrons are detected, forming an image”

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13
Q

advantages of SEMs

A

“They can be used on thick or 3-D specimens

They allow the external, 3-D structure of specimens to be observed”

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14
Q

disadvantages of SEMs (6)

A

“They give lower resolution images (less detail) than TEMs
They cannot be used to observe live specimens (unlike optical microscopes that can be used to observe live specimens)
They do not produce a colour image (unlike optical microscopes that produce a colour image)
Expensive to buy and operate
Complex sample preparation
Its not portable as its large and needs to be installed
“

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15
Q

advantages of laser scanning confocal microscopes

A

“They can be used on thick or 3-D specimens
They allow the external, 3-D structure of specimens to be observed
Very clear images are produced. The high resolution is due to the fact that the laser beam can be focused at a very specific depth
You can even see the structure of the cytoskeleton in cells”

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16
Q

disadvantages of laser scanning confocal microscopes

A

“It is a slow process and takes a long time to obtain an image
The laser has the potential to cause photodamage to the cells
“

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17
Q

what is the magnification and resolution of TEMs

A

“Magnification- x500,000

Resolution- 0.5nm”

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18
Q

“what is the magnification and resolution of SEMs

“

A

“Magnification- x500,000

Resolution- 3-10nm”

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19
Q

what is the magnification and resolution of light microscopes

A

“Magnification- x2000

Resolution- 200nm”

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20
Q

advantages of light microscopes

A 
"Inexpensive to buy and operate
Small and portable
Simple sample preparation
Specimens can be living or dead
Natural colour can be seen
"
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21
Q

how to laser scanning confocal microscopes work

A

“The cells being viewed must be stained with fluorescent dyes
A thick section of tissue or small living organisms are scanned with a laser beam
The laser beam is reflected by the fluorescent dyes

Multiple depths of the tissue section/organisms are scanned to produce an image”

22
Q

how do light microscopes work

A

“Light is directed through the thin layer of biological material that is supported on a glass slide
This light is focused through several lenses so that an image is visible through the eyepiece
The magnifying power of the microscope can be increased by rotating the higher power objective lens into place”

23
Q

list of rules for scientific drawing (7)

A

“-include a title

  • scale
  • sharp pencils
  • use as much of paper as possible
  • no shading
  • smooth continuous lines
  • label lines should not cross and no arrow heads”
24
Q

Functions and structure of cell surface membrane

A

“The membrane found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. Made up of lipids and proteins
Regulates the movement of substances into and out of the cell. It has receptor molecules on it which allows it to respond to chemical like hormones”

25
Q

function and structure of cell wall

A

“Found in plant cells but not in animal cells
Cell walls are formed outside of the cell membrane and offer structural support to cell
Structural support is provided by the polysaccharide cellulose in plants, and peptidoglycan in most bacterial cells”

26
Q

function and structure of the nucleus

A

“A large organelle surrounded by a nuclear envelope which contains many pores. The nucleus contains chromatin which is made from DNA and proteins and a structure called the nucleolus
It controls the cells activities. DNA contains instruction to make proteins. The pores allows substances to move between the nucleus and cytoplasm. The nucleolus makes ribosome
“

27
Q

function and structure of mitochondria

A

“Double membrane. The inner one is folded to form structures called cristae. Inside is the matrix which contains enzymes involved in respiration
It is the site of aerobic respiration where ATP is produced.
Found in large number of cells that are very active and require lots of energy”

28
Q

function and structure of ribosomes

A 
"Found in all cells
Found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
It’s made up of proteins and RNA.
No membrane
Site where proteins are made"
29
Q

function and structure of smooth ER

A

“System of membraned enclosing a fluid filled space.

Synthesises and produces lipids”

30
Q

function an structure of rough ER

A

“System of membrane enclosing a fluid filled space. Surface covered with ribosomes.
Folds and processes proteins that have been made at the ribosomes”

31
Q

function and structure of the Golgi apparatus

A

“A group of fluid filled membrane bound flattened sacs. Vesicles often seen at the edges of the sacs
It processes and packages new lipids and proteins and makes lysomes”

32
Q

function and structure of vesicles

A

“A small fluid filled sac in the cytoplasm surrounded by a membrane
Transports substances in and out of the cell “

33
Q

functions and structure of lysosomes

A

“A round organelle surrounded by a membrane

Contains digestive enzymes used for digesting invading cells or to break down worn out components of the cell”

34
Q

function and structure of the chloroplast

A

“A small flattened structure found in plant cells. Its surrounded by a double membrane and has thylakoid membranes inside. These membrane are stacked up to form gran which are linked together by lamellae.
Site where photosynthesis stakes places. Some happens in the Grana and other happens in the stroma which is a thick fluid found in the chloroplast

”

35
Q

function and structure of centrioles

A

“Small hollow cylinders made of microtubules. Found in animal cells and some in plant cells.
Involved with the separation of chromosomes during cell division”

36
Q

function and structure of microtubules

A

“Found in all eukaryotic cells
Makes up the cytoskeleton of the cell about 25 nm in diameter
Made of α and β tubulin combined to form dimers, the dimers are then joined into protofilaments
Thirteen protofilaments in a cylinder make a microtubule
The cytoskeleton is used to provide support and movement of the cell
Microtubules are tubular (hollow) strands”

37
Q

“function and structure of microfilaments

“

A

“Microfilaments are solid strands that are mostly made of the protein actin. These fibres can cause some cell movement and the movement of some organelles within cells by moving against each other
“

38
Q

functions of intermediate fibres

A

“These fibres give mechanical strength to cells and help maintain their integrity
“

39
Q

function of the capsule in prokaryotic cells

A

“It helps to protect bacteria from drying out and from attack by cells of the immune system of the host organism
“

40
Q

function of the pili

A

To stick to other cells or surfaces

41
Q

production and secretion of proteins

A

“Nucleus- mRNA transcribes RNA base sequence and it leaves through the nuclear pores
RER(ribosomes)-protein synthesis happens RNA
Transport vesicle protects the proteins from other chemical reaction and transport them to the Golgi apparatus
The Golgi further processes the proteins
Secretory vesicles bund to the plasma membrane and exocytosis occurs
“

42
Q

Function and structure of cilia

A

“Small hair like structures found on the surface membrane of some animal cell, they have an outer membrane and ring of nine pairs of protein microtubules inside with two microtubule in the middle (9 + 2 formation)
Microtubules allow the cilia to move high is used by the cell to move substances along the surface”

43
Q

Structure and function of flagellum

A

Flagella on eukaryotic cells are like cilia but long, they stick out of the cell surface and are surrounded by the plasma membrane. Also has 9+2 formation. The microtubules contract to make the flagellum move. It is used like outboard motor to propel cells forward.

44
Q

What is methylene blue used for

A

A dye used to stain DNA

45
Q

What is the equation linking magnification, image size and actual size

A

I = M x A

46
Q

Unit conversions

A

mm to um to nm

47
Q

Staining samples for light microscopes

A

Use some type of dye such as methylene blue or eosin. The stain is taken up by some parts more then the other and the contrast makes the different parts show

48
Q

What is eosin used for

A

A dye used to stain cell cytoplasm
pink

49
Q

Staining samples for electron microscopes

A

Objects are dipped into heavy metals like lead. The metal ions scatter the electrons creating contact which makes some parts seem darker then others.

50
Q

use of the different microscopes

A

light: to look at whole cells and tissues
SEM: to look at cell surface
TEM: to look at organelle detail

bio (13 decks)

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