2.1.1 CELL STRUCTURE

Question 1

Eukaryotic cells

Answer 1

-larger
-linear DNA
-has nucleus
-multicellular
-flagella made of micro tubes in 9+2 formation
-big ribosomes
-has introns AND exons

Question 2

Prokaryotic cells

Answer 2

-smaller
-circular DNA
-no nucleus
-unicellular
-flagella (made of flaggelin) on helix
-small ribosomes
-no introns(only coding DNA)

Question 3

Features of an animal cell

Answer 3

CELL SURFACE(PLASMA) MEMBRANE (lm+em) –>CILIA
CYTOPLASM(lm+em)
MITOCHONDIRA(lm+em)
LYSOSOMES(em)
(FREE FLOATING) RIBOSOMES(em)
ROUGH ENDOPLASMIC RETICULUM(em)
GOLGI APPARATUS(em)
SMOOTH ENDOPLASMIC RETICULUM(em)
VESICLES(em)
CENTRIOLES(lm+em)
NUCLEOLUS(lm)
NUCLEAR ENVELOPE(em)
NUCLEUS(lm+em)
FLAGELLA

Question 4

Features of plant cells

Answer 4

CELL WALL (with plasmodesmata)
VACUOLE
CHLOROPLAST

Question 5

cell wall
💪💪💪

Answer 5

description: rigid structure made up of cellulose. freely permeable. has plasmodesmata(channels for exchanging substances)
function: supports plant cells’ structure.

Question 6

(permanent) vacuole

Answer 6

structure: single membrane, contains dissolved sugars and amino acids
function: energy source + temporary food storage
maintains turgidity in plants

Question 7

cell surface (plasma) membrane
🚪🛎️📞

Answer 7

description: made up of lipids and proteins.
function: -regulates movement of substances in and out of cell.
-has receptor molecules that allow them to respond to chemicals.

Question 8

nucleus
👷‍♂️🚦

Answer 8

structure: -separated from the cell contents by nuclear envelope with openings(nuclear pores)
-contains chromatin(made from DNA and proteins)
function: -controls protein synthesis, metabolism, cell division, and stores genetic info coded into DNA

Question 9

nuclear envelope

Answer 9

double membrane with small
nuclear pores which control entry and exits of materials

Question 10

nucleolus

Answer 10

produces ribosomes
composed of RNA and proteins
at least one in a nucleus

Question 11

lysosome
💂💂🏻💂🏿

Answer 11

description:
-membrane bound with no clear structure
-contains digestive/hydrolytic enzymes i.r lysozymes
function: digestive enzymes that eat up invading cells or break down worn out cell components

Question 12

ribosome
🥥🏭

Answer 12

description: free floating(no membrane), made of protein+RNA
function: site of protein synthesis

Question 13

RER
📦📦🧑‍🏭

Answer 13

description: ribosome covered surface, system of folded membranes continuous in the nucleus with flattened sacs inside them increasing SA(cisternae)
function: site of synthesis and transportation for proteins and glycoprotein made in the ribosome into vesicles

Question 14

SER
👴📦📦

Answer 14

description: same as RER with no ribosomes
function: synthesis, storage and transportation (in vesicles) of lipids and carbs

Question 15

vesicles
👶🚪

Answer 15

description: small fluid filled sacs, membrane bound
function: transport substances between organelles in and out of cell (via plasma membranes)

Question 16

golgi apparatus
👩‍👧📦

Answer 16

description: membrane bound, fluid filled flattened sacs (with vesicles at the edges)
function: modifies molecules transported from SER/RER to ensure they are transported to correct location i.e proteins and triglycerides
-makes lysosomes(vesicles with proteins in them)

Question 17

mitochondrion
🏃‍♀️🏃‍♀️🏃‍♀️🏃‍♀️🏃‍♀️🏃‍♀️🤞

Answer 17

description: double membrane- inner one folded to form cristae(has matrix inside which contains respiratory enzymes)
function: site of aerobic respiration, production of ATP, large numbers and very active

Question 18

centrioles
👩‍💼👨‍⚖️

Answer 18

description: small, hollow cylinders made up of microtubules
function: involved in separation of chromosomes/ organise spindle fibres during cell division

Question 19

cilia
🌁🌁

Answer 19

description: small, hair like extensions found on surface membrane of some animal cells. CROSS SECTION- has an outer membrane and a ring of 9 pairs of protein microtubules inside with one pair in the middle
Function: microtubules used by the cell to move substances along cell surface(unicellular/single cell), beat rhythmically

Question 20

flagellum
🚁🚁🚁

Answer 20

description: like cilia but tail like extensions and longer on eukaryotic cells. surrounded by plasma membrane and internally like cilia(two microtubules in the centre and 9 pairs around the edge) in eukaryotic cells
function: detects changes in cell’s environment
microtubules contract to make the flagellum move( theyre like motors that propel cell)

Question 21

chloroplast
🥼

Answer 21

description: -small,flattened structure found in plant cells. -surrounded by a double membrane, filled with thylakoids(which are flattened sacs contain chlorophyll), to increase SA that are stacked to make grana.(they are linked up by lamallae)
function: site of photosynthesis (some of it in the grana and some in stroma which is a THICK FLUID and contains ribosomes ,DNA and starch grains)
-chlorophyll absorbs light for photosynthesis

Question 22

bacteria cell structure

Answer 22

-DNA
-cell wall(made up of peptidoglycan)
-flagellum
-plasma membrane
-plasmids
-ribosomes

Question 23

what is the cytoskeleton?

Answer 23

network of protein threads arranged as microfilaments(made up of actin and help move&contract during cytokinesis) and microtubules(made of tubulin and determine cell shape)
and intermediate fibres(give the cell strength)

Question 24

function of cytoskeleton

Answer 24

-support organelles shape and stability
-holds organelles in place
-facilitates transport of organelles and materials. i.e movement of chromosomes
-makes up centrioles
-allows cells to change shape during endo/exocytosis

Question 25

protein production

Answer 25

-made at ribosomes
-RER ribosomes make proteins attached to cell membrane
-free floating ones make proteins that stay in the cytoplasm
-RER folds and processes proteins
-then transported to golgi in vesicles where they are modified
-put in more vesicles to be transported around the cell.

Question 26

specialised cells

Answer 26

-may have greater/fewer organelles
i.e leaf cells need many chloroplasts and sieve tubes have scarce organelles and are angular and hexagonal

Question 27

functions of a light microscope

Answer 27

-sample is placed on a slide on the stage
-light is focused through a series of lenses on the eyepiece
-rotating objective lens changes the magnification of the image
(start with low power objective lens to locate items in the field of view)
2D image of cells&tissues
-mag= x1500
-res= 100

Question 28

advantages of light microscope

Answer 28

-inexpensive
-portable
-simple sample prep
-living or dead specimens

Question 29

function of a laser scanning confocal microscope

Answer 29

-specimen is stained with a dye
-laser in the microscope is moved across the specimen causing the dye to fluoresce and give off light
-the light is passed through a pinhole to the detector which generates a HIGH resolution
-2D or 3D image

Question 30

advantages of lsc microscope

Answer 30

-simple sample prep
-living or dead specimens
-can see movement of living cells

Question 31

disadvantages of lsc microscope

Answer 31

-low mag and res compared to electron
-expensive to buy

Question 32

function of TEM

Answer 32

-detector picks up electrons transmitted through a specimen and focused to produce an image
-specimen is viewed in a vacuum to ensure the electron beams travel in a straight line.
-mag= x500 000
-res= 10.0

Question 33

why can a higher res be achieved for TEM and SEM

Answer 33

electrons have a much smaller wavelength than light

Question 34

disadvantages of TEM and SEM

Answer 34

-expensive to buy and operate
-large and needs installation
-complex sample prep
-risk of artefacts(objects that appear in the microscope that are not part of the sample i.e air bubbles)
-black and white images
-dead specimens

Question 35

difference between SEM and TEM

Answer 35

-SEM beams electrons across surface of the specimen and images are collected via reflection of electrons whilst in TEM , electrons are transmitted through the spec to create an image
-SEM creates 3D images, TEM only creates 2D images

Question 36

advantages of SEM

Answer 36

high res and mag
3D image

Question 37

advantages of TEM

Answer 37

-high res and mag
-2D images obtained which show appearance of organisms

Question 38

function of SEM

Answer 38

-detector picks up beam of electrons that are sent across surface of spec and reflected electrons are collected
-3D surface images
mag= x100 000
res= 10.0

Question 39

when is dry mount used?

Answer 39

useful for observing thin and small objects i.e parts of insects, pollen, hairs

Question 40

preparing dry mount spec

Answer 40

-slice spec into thin layer
-use tweezers to place it on the slide and put cover slip on top

Question 41

when is wet mount used?

Answer 41

-when spec is wet or liquid i.e tiny aquatic organisms

Question 42

preparing wet mount spec

Answer 42

-place small droplet of water on the slide
-place spec on top
-when inserting coverslip, stand it up straight and slower lower it tilted to prevent air bubbles
-add a stain to provide a contrast to distinguish between different structures in the sample

Question 43

what is an eyepiece graticule?

Answer 43

transparent ruler that is fitted in the light microscope eyepiece lens which offers an arbitrary scale which can be compared to a unit of measure
-can calculate length of the object being viewed
(usually 1mm long with 100 units)

Question 44

what is a stage micrometer?

Answer 44

scale fitted onto a coverslip that offers an accurate scale(units) with known divisons and is used to calibrate the value of the
eyepiece divisions at different magnifications.
(1mm long with 100 divisions)

Question 45

how to calibrate the graticule

Answer 45

Set up the microscope to the required magnification to view the sample.
Place a stage micrometer on the stage.
Line up the two scales (the stage and eyepiece graticules) and count the number of divisions on the eyepiece graticule equivalent to each division
on the stage micrometre. calculate the length of one eyepiece division by ratio.
-convert answer to micrometers

Question 46

what is magnification?

Answer 46

-how many times bigger an image viewed through a microscope is compared to the real object

Question 47

magnification formula

Answer 47

size of image/size of object

Question 48

what is meant by resolution?

Answer 48

the ability to see more detail/separate two objects

Question 49

why do optical microscopes have low resolution?

Answer 49

-can catch bigger wavelength of visible light so can only show bigger organelles

Question 50

why do election microscopes have a higher resolution?

Answer 50

-can detect smaller wavelengths of visible light so can see smaller organelles

Question 51

electron vs optical microscopes

Answer 51

-electron has better magnification or better resolution
-optical can view living specimens and produce colour images
-optical AND sem allow for thick sample sections and easier sample prep which reduces the risk of artefact
-lscm AND sem allow for 3D while light and SEM allow for 2D images
-SEM and TEM both use vacuums

Question 52

Conversions

Answer 52

cm= x10 = mm= x1000 = um= x1000 = nm