Module 2 Section 1: Cell Structure Flashcards

Question

Function of centrioles

Answer 1

Makes a copy of itself during cell division and then helps to form the spindle in cell division

Answer 2

‘Hair like’ extensions that protrude from some animal cell types. In cross section they have an outer membrane and a ring of nine pairs of protein microtubules inside with two microtubules in the middle. Known as a 9 +2 arrangement. Arrangement allows movement

Answer 3

sensory function (e.g.nose), beat creating a current to move fluid/mucous/objects For locomotion

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

Answer 8

The membrane found on the surface of animal cells and inside the cell wall of plant and prokaryotic cells A phospholipid bilayer. Composed of proteins and lipids

Answer 9

Regulates the movement of substances into and out of the cell. Contains receptor molecules which allow it to respond to chemicals such as hormones

Answer 10

Made of B-cellulose microfibrils– complex carbohydrate 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 11

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 12

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 13

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 14

The section of DNA encoded with the protein is transcribed onto mRNA The mRNA leaves the nucleus via the nuclear pores and arrives at the rough endoplasmic reticulum and attaches onto the ribosome and amino acids are used to form proteins The protein is packed into a vesicle ad moves along the microtubules to the Golgi apparatus and fuses into the Golgi The protein moves through the cisternae of the Golgi and is processed and structurally modified ( e.g. sugar is added ) The modified protein is repackaged into a secretory vesicle and the vesicle leaves the Golgi The vesicles travels along the microtubules and fuses with the plasma membrane and is released by exocytosis

Answer 15

Extremely small (less than 2 micrometres in diameter) DNA is circular No nucleus - DNA free in cytoplasm Cell wall made of a polysaccharide, but not cellulose or chitin Few organelles and no membrane bound organelles Flagella (when present) made of protein flagellin, arranged in a helix Small ribosomes e.g. E.coli bacterium

Answer 16

larger cells (about 10-100 micrometres in diameter) DNA is linear Nucleus present - DNA is inside nucleus No cell wall (in animals), cellulose cell wall (in plants) or chitin cell wall (in fungi) Many organelles - mitochondria and other membrane bound organelles present Flagella (when present) made of microtubule proteins arranged in a 9 + 2 arrangement Larger ribosomes e.g. human skin cell

Answer 17

Magnification = image size/ object size

Answer 18

Magnifications how much bigger the images in the specimen

Answer 19

Resolution is how detailed the image is It’s how well a microscope distinguishes between two points are close together If a microscope lens can’t separate two objects, then increasing the magnification won’t help

Answer 20

Light microscopes use light They have a lower resolution than electron microscopes – they have a maximum resolution of about 0.2 micrometers. So they are usually used to look at whole cells or tissues The maximum useful magnification of a light microscope is about X 1500

Answer 21

These are a special type of light microscope, laser scanning confocal microscope to use laser beams (intense beams of light) to scan specimen, which is usually tagged with a fluorescent dye The laser causes the dye to fluoresce – give off light This light is then focus through a pinhole onto a detector The detectors hooked up to a computer, which generates an image – the image can be 3-D Pinhole means that any out of focus light is blocked, so these microscopes produce a much clearer image of a normal light microscope Can be used to look at objects different depths in thick specimens

Answer 22

Electron microscopes use electrons instead of light to form an image they have a higher resolution than light microscopes so give more detailed images There are two kinds of electron microscopes: Transmission electron microscope ( TEM ) Scanning electron microscope ( SEM )

Answer 23

They use electromagnets to focus a beam of electrons, which is then transmitted through specimen Denser parts of the specimen absorb more electrons, which makes them look dark on the image you end up with. TEMs Are good because they provide high resolution images ( So they can be used to look at a range of organelles ) but they can only be used on thin specimens

Answer 24

They scan a beam of electrons across the specimen This knocks off electrons from the specimen, which are gathered in the cathode ray tube to form an image The images produced show the surface of the specimen and can be 3D But they give a lower resolution than images with TEMs

Answer 25

Maximum resolution: Light: 0.2 micrometers TEM: 0.0002 micrometers SEM: 0.002 micrometers Maximum magnification: Light: x1500 TEM: can be more than x 1,000,000 SEM: usually less than x 500,000

Answer 26

In light microscopes and TEM, the beam of light of electrons passes through the object The image is produced because some parts of the object absorb more light ( or electrons ) than others Sometimes the object in view is completely transparent which makes the whole thing look white as all the light or electrons pass straight through To avoid this, the object is stained

Answer 27

Staining for light microscopes include using dyes Common stains include methylene blue and eosin The stain is taken up by some parts of the object more than others - the contrast makes the different parts show up

Answer 28

Different stains make different things show up Methylene blue stains DNA Eosin stains the cell cytoplasm More than one stain can be used at once

Answer 29

Objects are dipped in a solution of heavy metals e.g. lead The metal ions scatter the electrons, creating a contrast Some parts of the object show up darker than others

Answer 30

Strip of clean glass or plastic Usually flat but some have a small dip or well in the centre You can either prepare a slide as a wet mount or dry mount

Answer 31

The specimen needs to let light through it in order to be able to be seen clearly under the microscope A thick specimen must be split into a thin slice to use on the slide Use forceps to pick up the specimen and put it in the middle of the slide Put a cover slip on top

Answer 32

Pipette a small drop of water on the slide Use forceps to place the specimen onto the drop of water Stand the coverslip up right next to the water droplet, then tilt and lower it so it covers the specimen, try to avoid air bubbles under it as they will obstruct the view Once the cover slip is in position, a stain can be added Place a drop of stain next to one edge of the cover slip Put a bit of paper towel next to the opposite edge, the stain will get drawn under the slip, across the specimen

Answer 33

Clip the slide onto the stage Select lowest powered objective lens Use coarse adjustment knob to bring the stage up to just below objective lens Look down eyepiece and use coarse wheel to lower the stage until a roughly clear image appears Adjust the fine focus wheel until a clear image is formed Then turn up the magnification to look at the image at a higher magnification

Answer 34

Can be used to know the size of the specimen The graticule is fitted onto the eyepiece. It’s a transparent ruler with numbers, but no units The stage micrometer is placed on the stage - it is a microscope slide with an accurate scale ( has units ) and is used to work out the value of the divisions on the eyepiece graticule at a particular magnification This means when the stage micrometer is replaced with the slide containing the specimen, you’ll be able to measure the size of the specimen

Answer 35

Peptidoglycan