Unit 2: Cells

Question 1

Eukaryotic- Describe role of Golgi apparatus in lipid absorption (3)

Answer 1

1) Modifies/ processes triglycerides
2) Combines triglycerides with proteins
3) Packages for release/exocytosis/forms vesicle

Question 2

Eukaryotic- Compared to Prokaryotic (7)

Answer 2

1) Bacterial cell much smaller than human
2) Bacterial cell has a cell wall, human cell doesn’t
3) Bacterial cell lacks a nucleus, human cell has nucleus
4) Bacterial cell lacks membrane-bound organelles, human cells has them
5) Bacteria has 70s ribosomes whereas humans has 80s
6) Bacteria DNA is circular, human DNA linear
7) Bacterial DNA ‘naked’ whereas human DNA is bound to histones

Question 3

Homogenisation and Ultracentrifugation- How to separate mitochondria? (4)

Answer 3

1) Break open cells/ homogenise cells
2) Remove debris by filtration
3) Centrifuge highest density organelle nuclei obtained as pellet at slowest speed
4) Mitochondria in 2nd pellet as less dense than nucleus/organelles in first pellet

Question 4

Microscopes- Resolution of image obtained by using electron microscope is higher than resolution of image obtained by optical microscope. Why?

Answer 4

Shorter wavelengths between electrons

Question 5

Microscopes- Advantage of electron microscope over optical microscope (2)

Answer 5

1) High resolution
2) Can see internal structure of organelles

Question 6

Microscopes- Advantages and limitation of Transmission Electron Microscope (TEM) (6)

Answer 6

Advantages: 1) Small objects can be seen
2) TEM has high resolution as wavelengths of electron shorter
Limitations:
3) Cannot look at living cell as cells be in vacuum
4) Must be thin specimen
5) Preparation may create artefact
6) Doesn’t produce colour image

Question 7

Prokaryotic- Name the biological molecule in bacterial cell wall?

Answer 7

Murein

Question 8

Eukaryotic- Describe role of mitochondria in secreting protein?

Answer 8

Many mitochondria releases ATP for movements of vesicles/protein-synthesis/Active Transport

Question 9

Eukaryotic- Name main biological molecule in cell membrane (1)

Answer 9

Phospholipids

Question 10

Eukaryotic, Give one feature of chloroplast that allows protein to be synthesised inside and describe on difference between this feature in chloroplast and eukaryotic cell? (2)

Answer 10

1) DNA
2) Circular but nuclear DNA is linear

3) Ribosomes
4) Are smaller than cytoplasmic ribosomes

Question 11

Homogenisation- Conditions required for cell homogenisation (3)

Answer 11

1) Ice cold- Slows/stops enzyme activity to prevent digestion of organelles
2) Buffered- Maintains pH so enzymes/proteins not denatured
3) Isotonic- Prevents osmosis so no shrinkage of organelles

Question 12

Eukaryotic- State three difference between DNA in nucleus of plant cell and DNA is prokaryotic cell (3)

Answer 12

(plant v prokaryote)
1) Histones v no histones
2) Linear v circular
3) No plasmids v plasmids
4) Introns v no introns
5) Longer v shorter

Question 13

Eukaryotic- Eukaryotic cells produce and release proteins. Outline role of organelles in production, transport and release of proteins from eukaryotic cells? (4)

Answer 13

1) DNA in nucleus is code for protein
2) Ribosomes/RER produce protein
3) Mitochondria produce ATP for proteinsynthesis
4) Golgi apparatus package/modifiy
5) Vesicles/RER transports
6) Vesicles fuse will cell membrane

Question 14

Eukaryotic- Identify two organelles in cells that enable production of glycoproteins?

Answer 14

Rough endoplasmic reticulum ribosomes and Golgi apparatus

Question 15

Eukaryotic- Name the main polymer that forms the following cell walls- plant and fungal cells?

Answer 15

Cellulose (plant)
Chitin (fungi)

Question 16

Prokaryotic- Give two features of all prokaryotic cells that aren’t features of eukaryotic cells? (5)

Answer 16

1) Cytoplasm with no membrane bound organelles
2) Single, circular DNA
3) DNA free in cytoplasm
4) DNA that not associated with histones
5) Cell wall that contains murein

Question 17

Eukaryotic- Describe role of Golgi body secreting protein?

Answer 17

Many Golgi vesicles transport protein to cell membrane

Question 18

Microscopes- Comparison of TEM and optical microscope? (8)

Answer 18

1) TEM uses electrons, optical uses light
2) TEM allows greater resolution
3) TEM see smaller organelles
4) TEM view only dead specimen, optical view live specimen
5) TEM doesn’t show colour, optical can
6) TEM requires thinner specimens
7) TEM requires complex preparation
8) TEM focus using magnets and optical uses glass lenses

Question 19

Suggest why scientists can use detergent to break open cells instead of homogenisation? (2)

Answer 19

1) Cell membranes made from phospholipid
2) Detergent dissolves membranes/ phospholipid bilayer

Question 20

Microscopes- Describe and explain one difference between TEM and SEM? (2)

Answer 20

1)- 3D image with SEM, not 2D
- Lower resolution with SEM
2) Because electrons deflected/ bounce off using SEM

Question 21

Why are viruses classed as non-living?

Answer 21

-Have no metabolism
-Cannot independently move/respire
-No nutrition

Question 22

Viruses- Give 2 features of all viruses? (3)

Answer 22

1) Attachement Proteins
2) Capsid
3) Nucleic Acid

Question 23

Eukaryotic- Give two structures found in all prokaryotic cells and in all eukaryotic cells? (4)

Answer 23

1) Cell surface membrane
2) Ribosomes
3) Cytoplasm
4) DNA

Question 24

Eukaryotic- Describe the role of one named organelle in digesting bacteria? (3)

Answer 24

1) Lysosomes
2) Fuses with vesicle
3) Releases hydrolytic enzymes

Question 25

Eukaryotic- Describe structure and function of the nucleus? (4)

Answer 25

1) Nuclear envelope- holds/stores genetic information for production of proteins 2) Nuclear pores- DNA replication 3) Chromosomes- Production of mRNA 4) Nucleolus- Production of rRNA/ribosomes

Question 26

Eukaryotic division- During the cell cycle, the amount of DNA in a cell changes...

Answer 26

Increases

Question 27

Eukaryotic division- State name given to the division of cytoplasm during the cell cycle?

Answer 27

Cytokinesis

Question 28

Bacteria- Describe binary fission in bacteria? (3)

Answer 28

1) Replication of circular DNA 2) Replication of plasmids 3) Division of cytoplasm to produce daughter cells

Question 29

Eukaryotic Division- Suggest why preventing the formation of a spindle fibres stopped the cell cycle (4)

Answer 29

1) Chromosomes/chromatids cant attach to spindle 2) So, no metaphase 3) Chromatids cannot separate on spindle 4) So, no anaphase

Question 30

Eukaryotic Division- Describe the role of the spindle fibres and the behaviour of the chromosomes during mitosis (6)

Answer 30

1) In prophase, chromosomes condense 2) In prophase/metaphase, centromeres attach to spindle fibres 3) In metaphase, chromosomes/ sister chromatids line up at equator of the cell 4) In anaphase, centromeres divide 5) In anaphase, chromatids from each pair pulled to opposite ends of cell 6) In prophase/metaphase/anaphase, spindle fibres shorten

Question 31

Eukaryotic Division- Chromosomes behaviour in all stages (8)

Answer 31

1+2) In prophase, chromosomes coil/condense, chromosomes appears as two sister chromatids joined at centromere 3,4+5) During metaphase, chromosomes line up at equator, centre of cell, chromosomes attach to spindle fibres, by their centromere 6+7) centromere splits and divides and sister chromatids/chromosomes pulled apart to opposite poles and separate 8) Chromatids/chromosomes uncoil/unwind

Question 32

Eukaryotic Division- What is a tumour? (2)

Answer 32

1) Mass of cells 2) Many cells in mitosis/uncontrolled division

Question 33

Eukaryotic Division- Describe and explain arrangement of genetic material in prophase? (2)

Answer 33

1) Chromosomes becoming visible/distinct 2) Because they still condensing 3) Chromosomes arranged at random/not lined up 4) Because no spindle activity

Question 34

Viruses- Describe viral replication (5)

Answer 34

1) Attachment proteins attach to receptors 2) Virus injects nucleic acid into host cell 3) Host cell replicates viral nucleic acid 4) Host cell produces protein/capsid/enzyme 5) Virus assembled and released

Question 35

Bacteria- Describe now bacteria divide (4)

Answer 35

1) Binary Fission 2) Replication of circular DNA 3) Division of cytoplasm to produce 2 daughter cells 4) Each with single copy of circular DNA

Question 36

Eukaryotic division- Describe the appearance of chromosomes in anaphase

Answer 36

Chromatids are being pulled to opposite poles/ends by spindle fibres

Question 37

Eukaryotic Division- Evidence for a cell in anaphase (2)

Answer 37

1) Chromosomes/chromatids are at poles of spindle/ends of spindle 2) V-shape shows sister chromatids have been pulled apart at their centromeres

Question 38

Explain how the behaviour of chromosomes causes these changes in the amount of DNA per cell

Answer 38

1) Chromosomes/DNA replicates 2) Homologous chromosomes separate 3) Sister Chromatids separate

Question 39

Eukaryotic Division- Suggest and explain how two environmental variables could be changed to increase growth rate of cells (10)

Answer 39

1) Increased concentration of glucose 2) Increased respiration 3) Increased concentration of oxygen 4) Increased respiration 5) Increased temperature 6) Increased enzyme activity 7) Increased concentration of phosphate 8) Increased ATP/DNA/RNA

Question 40

Why are viruses classed as acellular?

Answer 40

- No cell surface membrane -Not made of cells -No cytoplasm

Question 41

Eukaryotic Division- Scientists measured percentage change in tumour volume. Suggest why they recorded both

Answer 41

Percentage change: 1) To allow comparison as tumors may differ in volume/size Tumor Volume: 2) Tumors may differ in length/width/shape

Question 42

Eukaryotic Division- Give two pieces of evidence that the cell was undergoing mitosis?

Answer 42

- Chromosomes are visible because they have condensed - Chromosomes made up of chromatids because DNA has replicated -Chromosomes not arranged in homologous pairsM

Question 43

Membrane Structure- Describe how proteins arrange themselves in the membrane (2)

Answer 43

1) Hydrophobic parts of helix sit within the hydrophobic fatty acid tails of phospholipids 2) hydrophilic parts of helix to the inside as ions are charged/polar

Question 44

Transport methods- Name and describe 5 ways substances can move across the cell surface membrane into cells (5)

Answer 44

1) Simple diffusion of small, non-polar molecules down a diffusion gradient 2) Facilitated diffusion of larger/charged molecules down a concentration gradient via protein carrier/channel 3) Osmosis of water down a water potential gradient 4) Active transport of molecules against concentration gradient via protein carrier using ATP 5) Co-Transport of 2 different substances using a carrier protein

Question 45

Transport Methods- What two factors affected rate of facilitated diffusion? (2)

Answer 45

1) External concentration 2) Number of channel/carriers proteins

Question 46

Transport Methods- Suggests and explain two ways the cell-surface membranes may be adapted to allow transport of nutrients (4)

Answer 46

1) Membrane filed/large SA 2) Large number of protein channels/carriers for facilitated diffusion 3) Large number of protein carriers for active transport 4) Large number of protein for co-transport