Cell Structure And Microscopy Flashcards

Question

Function of plasma membrane

Answer 1

• Regulates the movement of substances into and out of the cell. • Contains receptor molecules (glycoproteins and glycolipids) which allow it to respond to chemical like hormones Cholesterol provides strength and reduces fluidity Certain proteins in the plasma membrane are used for transport

Answer 2

Made up of three structural component： Microfilaments Microtubules Intermediate fibres

Answer 3

Microfilaments- Fibres made from the protein actin. They are responsible for movement of the cell and cytoplasm during cytokinesis Microtubules- Formed by the globular protein tubulin. They polymerise to form tubes that determine the shape of the cell. They also act as tracks for organelles moving forward. Intermediate fibres- Gives strength to cells and helps maintain integrity.

Answer 4

similar to cilia but longer. • They protrude from the cell surface and are surrounded by the plasma membrane. • Like cilia they have a 9 +2 arrangement.

Answer 5

• (Whip-like) enables a cells mobility. • The microtubules contract to make the flagellum move. • Propel cells forward e.g. sperm cells.

Answer 6

• Double membrane which encloses the stroma. • Stroma contains: Starch grains, lipid stores, DNA, RNA, ribosomes. • Series of membrane-bound flattened sacs called thylakoids in the stroma. Thylakoids stacked together are called grana. • Grana are linked together by lamellae. • The grana contain chlorophyll

Answer 7

Photosynthetic reactions The stroma contains enzymes for the light-independent stage of photosynthesis.

Answer 8

Made of B-cellulose microfibrils (complex carbohydrate) in plants / chitin (fungi) / polysaccharides (prokaryotic) • Cell wall is fully permeable to substances • Thin layer called the middle lamella which marks the boundary between adjacent cell walls and ‘cements’ adjacent cells together.

Answer 9

Gives the plant mechanical strength • Gives the plant cell support and it’s shape • Contents of plant cell can ‘push’ against the cell wall (turgid cell). This gives the cell (and the whole plant) good support.

Answer 10

• Single membrane bound (membrane is called a tonoplast). • Contains a fluid called cell sap (solution of mineral salts, sugars, amino acids, wastes etc). • Selectively permeable barrier

Answer 11

• Stores cell cap • Support herbaceous plants by making cells turgid. • Helps maintain shape and gives support by maintaining ** turgor pressure** . • Sugars and amino acids act as a temporary food store.

Answer 12

1)DNA in the nucleus contains the genetic code to make protein. 2) The particular gene (e.g. insulin) is copied by mRNA, which takes the copy of the gene out of the nucleus via the nuclear pore to the ribosome (on the rough ER). 3) The protein is synthesized on the ribosome bound to the Rough ER where it then passes into the cisternae of the rough ER and it is packaged into a vesicle. 4) The vesicle moves to the golgi apparatus (via the microtubules of the cytoskeleton), and fuses with the golgi apparatus. 5) The protein enters the golgi apparatus where it processes and structurally modifies the protein e.g. adds a carbohydrate chain. 6) The Golgi Apparatus repackages the protein into a secretory vesicle where it travels along the microtubules and fuses with the cell surface membrane. 7) Contents of the vesicle (i.e. the protein) is released by exocytosis.

Answer 13

How many time bigger the image produced by the microscope is than the real life object

Answer 14

The ability to distinguish between two objects that are close together (seeing two structures that are very close as two separate objects)

Answer 15

Eyepiece lens magnification X objective lens = Total magnification

Answer 16

Image size ————————— Actual size X Magnification

Answer 17

Microscopes are used to analyse the cell components and observe organelles (sub cellular structure)

Answer 18

Optical microscopes use light to form an image. This is done through the lamp at the bottom of the microscope which is connected to a power source.

Answer 19

inexpensive to buy and operate Small and portable simple sample preparation vacuum not required Specimen can be living or dead

Answer 20

Limited resolution- 0.2micrometres or 200nm Can’t distinguish between two objects that are closer than the wavelength of light 500-650nm Maximum useful magnification of x1500 Cannot observe ribosomes, ER or lysosomes

Answer 21

Electron microscopes use electrons to form an image. A beam of electrons is fired at the specimen which has a much smaller wavelength than light. The electron microscope can resolve two objects that are extremely close together and are absorbed by air thus must be in a vacuum.

Answer 22

Maximum resolution of 0.2nm (1000x greater than optical microscopes) over x500,000 magnification

Answer 23

Expensive to buy and operate Large and needs to be installed Complex sample preparation Sample preparation often distorts material Vacuum required Specimens are dead Black and white images produced

Answer 24

SEMs scan a beam of electrons across the surface of the specimen This bounces off the surface and scatters the electrons which are detected, forming an image SEMs therefore form a 3D image that shows the surface of a specimen

Answer 25

3D images are formed that shows the surface of a specimen Magnification is x500,000 or less Can be used on thick or 3d specimens Allows external 3d structures to be observed

Answer 26

Lower resoltuions than TEMs Cannot be used on live specimens (unlike microscopes) Do not produce a colour image (unlike optical microscopes) Note images are often digitally processed (enhanced)

Answer 27

TEMs use electromagnets to focus a beam of electrons, which is transmitted through the specimen Denser parts of the specimen absorb more electrons, making them appear darker on the final image (contrast between the different parts being observed) 2D image is produced which shows the detailed internal structure of cells

Answer 28

Higher resolution images = more detail Internal structure can be seen Magnification is x1,000,000 or more

Answer 29

Only used with very thin specimens or thin sections of an object Cannot be used to observe live specimens because of the vaccum inside the TEm plus all the water must be removed from the specimen Lengthy treatement require to prepare specimens. Artefacts could be introduced these look like real structures but are actually the result of preserving or staining. Do not produce a colour image and 2D

Answer 30

A thick section of tissue or small living organism is viewed at a high light intensity with fluorescent dyes The laser beam is reflected by the fluorescent dye Multiple depths of the tissue section/ organism are scanned to produce an image. As if the laser beam is building the image layer by layer . A 3D or 2D image can be created in different focal planes

Answer 31

Used on thick or 3d specimens External 3d structure is observed Very clear and high resolution because the laser beams can be focused at a very specific depth. Cytoskeletons can be observed

Answer 32

Slow process and takes a long time to obtain an image Laser could cause photodamage to cells

Answer 33

÷ 1000 ÷ 1000 ÷ 10 ÷ 100 ÷ 1000

Answer 34

Step 1: Circle what the question is asking for. Step 2:Measure the image (if that is required) Step 3: Write out what you know (I=, A=, M=) Step 4: Write formula, convert units and sub in the values

Answer 35

Magnification = measured length of scale bar ————————————————————- actual length of scale bar

Answer 36

A photo-micrograph is a photo or digital image taken through a microscope to show a magnified image of a specimen.

Answer 37

Mitochondria– Cells with many mitochondria typically undertake energy-consuming processes (e.g. neurons, muscle cells)

Answer 38

Cells with extensive ER networks undertake secretory activities (e.g.plasma cells, exocrine gland cells)

Answer 39

Cells rich in lysosomes tend to undertake digestive processes (e.g. phagocytes)

Answer 40

Cells with chloroplasts undergo photosynthesis (e.g. plant leaf tissue but not root tissue)

Answer 41

Many tissues that are used in microscopy are transparent, letting light and electrons through them. This makes it difficult to see details. Stains are often used to color the tissues

Answer 42

Coloured dyes are dropped with a pipette when staining specimens. They absorb specific colors of light whilst reflecting others, making the structure visible. Certain tissues absorb certain dyes, depending on their chemical nature. Sometimes specimens are stained with more than one dye to ensure different tissue show up (differential staining) Most colors are not natural

Answer 43

Toluidine blue , methylene blue , phloroglucinal and eosin are common stains

Answer 44

When using electron microscope the specimen must be stained to absorb/ scatter the electrons Electrons have no colour so dyes used cause the tissue to show up black or different shades of grey

Answer 45

Heavy metal compounds are commonly used as stains because they provide a good contrast by absorbing/ scattering electrons. For example osmium tetroxide and Ruthenium tetroxide Any colour present in electron micrograph is unnatural and not as a result of staining Colour usually added using an image processing software

Answer 46

- Attached to the eyepiece of the microscope - Has a scale, but NO UNITS - It always remains constant therefore it needs to be recalibrated for each objective lens (x4, x10, x40)

Answer 47

- this is a microscopic ruler on a special slide with a tiny scale etched on it (in µm) - The ruler is 1mm long, and divided into 100 divisions. - This scale is very accurate. Each division is 0.01mm or 10 µm

Answer 48

Differential staining is a technique which involves many chemical stains being used to stain different parts of a cell in different colours.

Answer 49

They are positively charged, and therefore are attracted to and stain negatively charged materials.

Answer 50

Nigrosin and Congo red are negatively charged, and therefore cannot enter the cells because cytosol repels them. This creates a stained background, and the unstained cells then stand out.

Answer 51

Common use of differential staining. Two different stains are used- crystal violet and safranin Crystal violet is added, then iodine to fix the stain, and then alcohol is used to wash away any unbound stain. Gram-positive bacteria appear blue/purple as the stain is retained due to the thicker peptidoglycan cell wall later absorbing the dye.

Answer 52

Being able to distinguish between the two types of bacteria helps medics to prescribe an appropriate antibiotic to patients with bacterial infections, e.g., penicillin can be used to treat gram-positive bacteria but not gram-negative

Answer 53

Most eukaryotic cells are complex multicellular organisms containing a range of specialised cells to perform a variety of functions.

Answer 54

Organisms are made up of organ systems, which contain a range of organs working together to perform a function.

Answer 55

Organs are made up of a range of tissues working together to perform a function

Answer 56

A tissue is a group of cells that work together to perform a particular function.

Answer 57

Surrounded by a double membrane nuclear envelope with nuclear pores. Contains chromosomes, consisting of protein- bound, linear DNA, and one or more nucleolus.

Answer 58

Prokaryotic cells are single-celled organisms that lack a nucleus and other membrane-bound organelles.

Answer 59

cytoplasm does not contain any membrane-bound organelles The ribosomes are smaller, (70S in size in prokaryotes). Bacteria still contain DNA, but it is not stored in a nucleus. The DNA is found as a single, circular molecule in the cytoplasm and it is not associated with histone proteins. Prokaryotic cells do have cell walls made up of a glycoprotein called murein. They can contain plasmids, which are rings of DNA containing genes linked to survival such as antibiotic resistance. Surrounding the cell wall, some bacteria have a capsule which is to provide protection from other cells and to help bacteria stick together. Flagella which used for locomotion.

Answer 60

Common use of differential staining. Two different stains are used- crystal violet and safranin Crystal violet is added, then iodine to fix the stain, and then alcohol is used to wash away any unbound stain. Gram-negative bacteria cannot absorb crystal violet stain as their peptidoglycan cell wall is thin and so do not retain the stain due to having thinner walls. Therefore, safranin is used as a counterstain, turning them red.

Answer 61

• Do have a nucleus • Do have membrane- bound organelles • Includes all animal and plant cells Contains Ribosomes (80S) Contains a cytoskeleton Contains centrosomes

Answer 62

Use a sharp pencil and ruler Draw with an underline with annotations Use smooth continuous lines to draw, no overlapping and no gaps No shading or coloring in Be accurate when drawing Drawing must take 50% of the box Labels should be straight and parallel to the drawing. Arrows should not be used Labels should touch the cell that is being labeled Include scale/ magnification No cross-hatching

Answer 63

Use a stage micrometer. This is a microscope slide with an accurate scale etched on it and insert the graticule into the eyepiece lens and line up the two scales. It is then possible to count the number of divisions on the eyepiece graticule equivalent to each division on the stage micrometer and calculate the length that one eyepiece division is equivalent to.

Answer 64

Place the slide showing the specimen on the microscope stage. Looking from the side at eye level , twist the focusing dial until themicroscope stage has moved up so that the slide is just about to touch the lens. Then use the coarse focusing dial to focus DOWN until you can clearly see the cells in the field of view. (Make sure the cells are in the centre of the field of view) Use the smallest power objective and focus until you can see the cell . Then rotate to the medium power lens and again focus until you can see the cells clearly. Lastly, switch to the highest power objective lens. Use the eyepiece graticule to measure the length of cells Make scientific annotated drawings of the stages of a selection of cells.

Answer 65

200nm 2nm 0.2nm 0.2nm>

Answer 66

X1500 X500,000 X1,000,000 X1,000,000<

Cell Structure And Microscopy Flashcards

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