Basic structure of living systems

Question 1

Dry mount preparation

Answer 1

• solid species viewed whole or cut into thin slices with a sharp blade
• specimen placed on centre of slide and cover slip placed over sample
• Eg. hair, pollen, dust

Question 2

Wet mount

Answer 2

• specimens viewed suspended in water or immersion oil
• cover slip placed on from angle
• Eg. aquatic samples

Question 3

Squash slides

Answer 3

• wet mount is prepared
• lens tissue used to gently press down on cover slip
• damage to cover slip can be avoided by squashing between 2 microscope slides
• Eg. root tip squashes to look at cell division

Question 4

Smear slides

Answer 4

• edge of a slide used to smear sample creating thin even coating
• cover slip placed over sample
• Eg. blood samples to view cells

Question 5

why is staining used?

Answer 5

• easier to distinguish between different components under microscope - more visible

Question 6

examples of stain that can be used to see nuclei?

Answer 6

methylene blue,

Question 7

Rules for scientific drawing

Answer 7

• title
• magnification
• sharp pencil plane white paper
• no sketch lines
• no shade
• labels
• correct proportions
• label lines with ruler, not crossing and no arrow heads

Question 8

magnification definition and equation

Answer 8

how many times larger the image is than the actual size of the specimen
actual size=image/magnification

Question 9

resolution

Answer 9

ability to distinguish between 2 close together objects

Question 10

light microscope magnification and resolution

Answer 10

• x1500
• 250nm

Question 11

Transmission electron microscope - how does it work and magnification

Answer 11

• electrons pass through and around specimen, giving contrast
• 2D
• x 500,000

Question 12

Scanning electron microscope - how does it work and magnification

Answer 12

• electrons reflect off sample - do not go through or pass around
• 3D
• x 100,000

Question 13

why can’t electron microscopes see in colour?

Answer 13

• there is only one wavelength transmitting (electrons) rather than visible light

Question 14

advantages of electron microscope

Answer 14

• 0.2nm resolution - 100x more than light microscope
• structured detailed images of organelles in cells
• SEM is 3D - uncovers details of cellular tissue arrangement

Question 15

disadvantages of electron microscopes

Answer 15

• electron beams deflected by air molecules so sample need to be in vacuum - has to be dead
• expensive - £250,000
• preparing slides requires high skill level and training

Question 16

what is eukaryote?

Answer 16

• organism with one or more cells containing DNA in membrane-bound nucleus

Question 17

Nucleus function

Answer 17

• houses nearly all cells’ genetic material

Question 18

chromatin

Answer 18

• consists of DNA and histones (proteins)
• found in nucleus
• seen as darker patches on light micrograph

Question 19

nucleolus

Answer 19

• makes RNA which is made into ribosomes - move out of nucleus to outside of rough endoplasmic reticulum
• found in nucleus

Question 20

nuclear envelope

Answer 20

• surrounds nucleolus
• made of inner and outer membranes with fluid separating them
• marked with nuclear pores for exchange of large molecules

Question 21

mitochondria

Answer 21

• energy generator
• has inner and outer membrane
• inner membrane covered in enzymes to catalyse aerobic respiration to produce ATP
• 2-5 micrometers long

Question 22

cristae

Answer 22

• found in mitochondria
• inner membrane folds inwards - inner folds are cristae
• project into matrix

Question 23

matrix

Answer 23

• liquid inside inner membrane of mitochondria

Question 24

ribosomes

Answer 24

• found in cytoplasm or rough endoplasmic reticulum
• consists of 2 sub-units
• site of protein-synthesis - where proteins are made
• acts as assembly line for coded info from nucleus to be used to make proteins from amino acids

Question 25

Golgi apparatus

Answer 25

- stack of membrane-bound flattened sacs - receives proteins and modifies them - may add sugar molecules - packages modified proteins into vesicles to be transported

Question 26

lysosomes

Answer 26

- spherical sacs surrounded by single membrane - specialised vesicles containing digestive enzymes to break down materials

Question 27

rough endoplasmic reticulum

Answer 27

- consists of flattened membrane-bound sacs called cisternae - studded with ribosomes - transports proteins made on ribosomes - some proteins secreted, others placed on surface of cell membrane

Question 28

smooth endoplasmic reticulum

Answer 28

- same structure as rough endoplasmic reticulum but no ribosomes - involved in making lipids the cell needs

Question 29

centrioles

Answer 29

- self-replicating organelles made up 9 bundles of microtubules - 9+2 arrangement - only found in animal cells - help in organising cell division - form spindle fibres

Question 30

cilia and flagella function

Answer 30

- locomotion in individual organisms - move fluid or materials past a cell or group of cells in multi-cellular organisms

Question 31

chloroplasts

Answer 31

- use CO2, water and light to build sugars - present in all green plants - double membrane bound

Question 32

stroma

Answer 32

- liquid in chloroplasts - 1st stage of photosynthesis - contains sacks of thylakoid membranes called grana - 2nd stage photosynthesis

Question 33

vacuole

Answer 33

- have membrane called tonoplast filled with cell sap - important in keeping cell turgid

Question 34

cell wall

Answer 34

- gives support and structure - made of cellulose - can act as carbohydrate store - has plasmodesmata - pores to let substances in and out and connect cells together

Question 35

endosymbiosis theory

Answer 35

- mitochondria and chloroplasts were formerly free-living bacteria (prokaryotes) - these were taken inside another cell as an endosybiont - led to evolution of eukaryotic cells

Question 36

DNA in prokaryotes

Answer 36

- generally only one molecules of DNA - a chromosome super coiled to make it compact

Question 37

ribosomes in prokaryotes

Answer 37

- smaller than eukaryote's - eukaryotes - 80S, prokaryotes - 70S - not involved in formation of more complex proteins

Question 38

what is cell wall prokaryotes made of?

Answer 38

- peptidoglycan or murein - complex polymer made from amino acids and sugars

Question 39

flagella prokaryotes

Answer 39

- thinner than eukaryote's - does not have 9+2 arrangement - energy to rotate flagella is formed not from ATP - attached to cell membrane by a basal body and rotated by molecular motor

Question 40

main components of cytoskelton

Answer 40

microfilaments (narrowest), intermediate fibres, microtubules (widest)

Question 41

microfilaments

Answer 41

- narrow fibres containing the protein actin - actin fibres contract - invovled in cell movement eg. white blood cell out of blood into infected tissue - process of cytokinesis involves microfilaments

Question 42

intermediate fibres

Answer 42

- made of lots of different proteins - strenghthen cell eg. skin cells under constant stress - help prevent stresses damaging them

Question 43

microtubules

Answer 43

- part of cytoskeleton - tubulin proteins form hollow tubes - act as tracks for movement of organelles eg. vesicles movement during secretion - form spindle fibres in cell division

Question 44

cytoskeleton functions

Answer 44

- movement of cell - movement of organelles - strengthening/support of cells - forming spindle in mitosis/meiosis - movement of chromosomes