cell structure

Question 1

Define magnification

Answer 1

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

Question 2

Define resolution

Answer 2

The ability to see individual objects as separate entities

Question 3

how to prepare dry mount

Answer 3

“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”

Question 4

how to prepare wet mount

Answer 4

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

Question 5

how to prepare squash slide

Answer 5

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

Question 6

how to prepare smear slide

Answer 6

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.

Question 7

why is staining used in microscopic

Answer 7

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

to see certain names organelles

Question 8

what is differential staining

Answer 8

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

Question 9

how do transmission electron microscopes work

Answer 9

“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”

Question 10

advantages of TEMs

Answer 10

“They give high-resolution images (more detail)

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

Question 11

disadvantages of TEMs (6)

Answer 11

“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
“

Question 12

how do SEMs work

Answer 12

“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”

Question 13

advantages of SEMs

Answer 13

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

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

Question 14

disadvantages of SEMs (6)

Answer 14

“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
“

Question 15

advantages of laser scanning confocal microscopes

Answer 15

“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”

Question 16

disadvantages of laser scanning confocal microscopes

Answer 16

“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
“

Question 17

what is the magnification and resolution of TEMs

Answer 17

“Magnification- x500,000

Resolution- 0.5nm”

Question 18

“what is the magnification and resolution of SEMs

“

Answer 18

“Magnification- x500,000

Resolution- 3-10nm”

Question 19

what is the magnification and resolution of light microscopes

Answer 19

“Magnification- x2000

Resolution- 200nm”

Question 20

advantages of light microscopes

Answer 20

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

Question 21

how to laser scanning confocal microscopes work

Answer 21

“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”

Question 22

how do light microscopes work

Answer 22

“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”

Question 23

list of rules for scientific drawing (7)

Answer 23

“-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”

Question 24

Functions and structure of cell surface membrane

Answer 24

“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”

Question 25

function and structure of cell wall

Answer 25

"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"

Question 26

function and structure of the nucleus

Answer 26

"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 "

Question 27

function and structure of mitochondria

Answer 27

"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"

Question 28

function and structure of ribosomes

Answer 28

``` "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" ```

Question 29

function and structure of smooth ER

Answer 29

"System of membraned enclosing a fluid filled space. | Synthesises and produces lipids"

Question 30

function an structure of rough ER

Answer 30

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

Question 31

function and structure of the Golgi apparatus

Answer 31

"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"

Question 32

function and structure of vesicles

Answer 32

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

Question 33

functions and structure of lysosomes

Answer 33

"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"

Question 34

function and structure of the chloroplast

Answer 34

"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 "

Question 35

function and structure of centrioles

Answer 35

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

Question 36

function and structure of microtubules

Answer 36

"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"

Question 37

"function and structure of microfilaments | "

Answer 37

"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 "

Question 38

functions of intermediate fibres

Answer 38

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

Question 39

function of the capsule in prokaryotic cells

Answer 39

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

Question 40

function of the pili

Answer 40

To stick to other cells or surfaces

Question 41

production and secretion of proteins

Answer 41

"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 "

Question 42

Function and structure of cilia

Answer 42

"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"

Question 43

Structure and function of flagellum

Answer 43

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.

Question 44

What is methylene blue used for

Answer 44

A dye used to stain DNA

Question 45

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

Answer 45

I = M x A

Question 46

Unit conversions

Answer 46

mm to um to nm

Question 47

Staining samples for light microscopes

Answer 47

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

Question 48

What is eosin used for

Answer 48

A dye used to stain cell cytoplasm pink

Question 49

Staining samples for electron microscopes

Answer 49

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

Question 50

use of the different microscopes

Answer 50

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