studying cells

Question 1

define eukaryotic

Answer 1

• true nucleus; dna enclosed in a nuclear membrane
• membrane bound organelles
  eg: plants, algae, animal, protozoan and fungi

Question 2

what structures are visible in an animal cell under a light microscope

Answer 2

nucleus
cell membrane

Question 3

how are epithelial cells adapted for their function/

Answer 3

• cell membrane folded into structures called microvili
  -microvili increase SA for absorption

Question 4

what is the function of the nucleus

Answer 4

contains genetic material
controlls cell activity

Question 5

describe the structure of the nucleus

Answer 5

• largest organelle
• douvle membrane/ nuclear envelope
• contains nucleolus which is where rRNA is made
• chromatin in nucleus coils around proteins called histones

Question 6

mitochondria

Answer 6

• site of aerobic respiration
• ATP production

Question 7

describe the structure of the mitochondria

Answer 7

outer membrane
inner membrane that folds to form cristae
cristae increase SA for atp synthase attachmemt
matrix - contains proteins, lipids, DNA and ribosomes

Question 8

Rough Endoplasmic Reticulum (RER)

Answer 8

• encrusted in 80s ribosomes
• site of protein synthesis
• transports and stores protein within a cell
• membrane folded into flattened sacks called cisternae

Question 9

smooth endoplasmic reticulum (SER)

Answer 9

• recombines glycerol and fatty acids to make triglycerides (site of lipid synthesis)
• pakcages triglycerides into vesicles and transports them to golgi apparatus

Question 10

ribosomea

Answer 10

site of protein synthesis
- made of rRNA and ribosomal proteins
eukaryotic: 80s, prokaryptic: 70s

Question 11

what is the function of the golgi apparatus

Answer 11

modifies and packages proteins and triglycerides into vesicles

Question 12

what is the function of a lysosome?

Answer 12

• contains digestive/ hydrolytic enzymes (lysozymes)
• hydrolyses damaged or worn out organelles

Question 13

cell surface membrane

Answer 13

• made of a phospholipid bilayer
• controls the passage of substances into and out of a cell
• can fold to increase SA

Question 14

what is the function of chloroplasts

Answer 14

contain thylakoids
stacks of thylakoid = granum
site of photosynthesis

Question 15

what is the function of the capsule

Answer 15

protects cells from immune systems
aids bacteria sticking together

Question 16

what is the function of the plasmid

Answer 16

circular DNA
contains antibiotic resistant genes

Question 17

what is the function of the cell wall

Answer 17

provides a rigid shape
stops osmotic lysis

Question 18

what is the function of the flagellum

Answer 18

allows movement

Question 19

what is the function of the centrioles

Answer 19

• forms a network of spindle fibres that attach to chromosomes
• pull chromosomes apart

Question 20

contrast a plant cell from an animal cell

Answer 20

carbs in animals glycogen, plants store carbs as starch (grains)
plants have chloroplasts, cellulose cell walls and permanent vacuole
plants have plasmodemata
animals have centrioles(

Question 21

chloroplast

Answer 21

granum = stack of thylakoid membranes
thylakoid = contains chlorophyll for PS and ATP synthase to produce ATP
STROMA - fluid
starch grains - energy storage molceule
- prokaryotic DNA, 70s ribosomes

Question 22

what is the function of the chloroplast

Answer 22

absorbs light energy for photosynthesis
products of PS/RP allows plant to grow

Question 23

cellulose cell wall

Answer 23

• very strong
• mnay weak hydrogen bonds between cellulose fibres
• stops osmotic lysis (bursting)
• wall is permeable unlike membrane
• plasmodemata allows cytoplasms to connect together

Question 24

what are the cell walls in fungi made out of?

Answer 24

chitin

Question 25

define prokaryotic cells

Answer 25

- no nucleus - no membrane bound organelels - circular DNA, no association with histones, no introns

Question 26

what is the cell wall of a bacterial cell made out of?

Answer 26

murein

Question 27

eukaryotic cells produce and release proteins. outline the role of organelles in the production, transport and release od proteins from eukaryotic cells.

Answer 27

- DNA in nucleus is code for protein - ribosomes/ RER produce protein - mitochondria produces ATP for protein synthesis - golgi apparatus modifies proteins and packages them in vesicles to transport - vesicles transport - vesicles fuse with the cell surface membrane

Question 28

compare and contrast the differences between euk and prokaryotic cells

Answer 28

similarities: - nucleotide structure identical - phosphodiester bonds - DNA in mitochodnria and chloroplasts are similar to DNA in prokaryotes Differences: - euk DNA is longer - euk DNA has introns - euk DNA is linear, prok is circular - euk associated with histones

Question 29

state three differences between DNA in the nucleus of a plant cell and DNA in a prokjaryotuc cell

Answer 29

- associated with introns - linear DNA - plants no plasmid - introns - longer

Question 30

the structure of a cholera bacterium is different to the structure of an epithelium cell from small intestines. describe how it is different.

Answer 30

- cholera bacteria is a prokaryote - no nucleus - no membrane bound organelles - no mitochondria/golgi/RER - 70s ribosomes only - capsule/ plasmid/ flagellum

Question 31

structure of a virus

Answer 31

- not living cells - either ss or ds DNA/RNA - attachment proteins - enzymes (reverse transcriptase)

Question 32

name two structures of a euk cell that can NOT be indentified with a light microscope

Answer 32

mitochondria ribosome lysosome cell surface membrane

Question 33

give one advantage of using a TEM rather than a SEM

Answer 33

higher resolution higher detail of image allows internal structures to be seen

Question 34

give one advantage of a SEM rathet than a TEM

Answer 34

3D images thin sections dont have t be prepared

Question 35

define resolution

Answer 35

ability to distinguish between 2 objects that are close together shorter wavelength = higher resolution

Question 36

scientists use optical microscopes and TEM to investigate cell sturtcure. explain the advantages and limitations of using a TEM

Answer 36

advantage: small objects can be seen TEM has hgiher resolution electron wavelength is shorter limitATIONS: cant look at living cells so cells dead must be in a vacuum so cells dead thin specimen so dead COMPLEX staining method so preparation may cause artefacts

Question 37

describe the principles of a TEM

Answer 37

- electrons pass through specimen - desner parts absorb more electrons - denser parts appear darker - electrons short wavelength so higher resolution

Question 38

a student views the impressions of stomata using an optical microscope. she measured the mean diameter of the stomata. descirb ehow the student could have used the eyepiece graticule to determine the mean number of stomata

Answer 38

- measure each stomata using the eyepiece graticule - calibrate the eyepiece graticule against a stage micrometer - take atleast 5 measurements and calculate a mean

Question 39

name 2 structures within a euk cell that can be identified using a TEM

Answer 39

mitochondria ribosome lysosome

Question 40

describe how you would make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical microscope

Answer 40

- add a drop of water to the microscope slide - thin section of plant tissue and float it on the drop of water - stain with KI solution - lower cover slip using a mounted needle to avoid air bubbles

Question 41

magnification equation

Answer 41

I/AM Image size - magnification x actual size - measure in mm, x1000 to get micrometres

Question 42

scientists isolated mitochondria from liver cells. they broke the cells open in an ice cold, buffered, isotonic solution. explain why,

Answer 42

- isotonic so no osmotic lysis of organelles - ice cold so no enzyme activity so organelles arent digested - buffered so maintains a constant pH so proteins dont denature

Question 43

order of density in centrifugation

Answer 43

1. nucleus 2. mitochondria/ chloroplast 3. ER/golgi 4. ribosomes

Question 44

describe and explain how cell fractionation and cell centifugation can be used to isolate mitochondria from a suspension of animal cells

Answer 44

- cell homogenisation to break open cell walls and release organelles - filter to remove large cellular debris - use isotonic solution to prevent damage to mitochondria - cold to prevent enzyme activity so no organelles are digested - buffer maintains pH, prevents enzyme denaturation - use differential centrifugation to separate nuclei - respin at higher speed for longer time to get mitochondrial pellet - observe the pellet in microscope to identify mitochondria

Question 45

describe how you could use cell fractionation to isolate chloroplasts from leaf tissue

Answer 45

- break open cell walls in a homogeniser and filter to remove cellular debris - place in isotonic, ice cold, buffered solution - use differential centrifugation - chloroplasts are second pellet