Cells

Question 1

Eukaryotic vs Prokaryotic Cells?

Answer 1

 Eukaryotic = animal/plant cell, has membrane bound organelles (nucleus, endoplasmic reticulum, golgi body, lysosome, mitochondra)
 Prokaryotic = bacteria, has no membrane bound organelles

Question 2

Structure of Nucleus?

Answer 2

 contains DNA (made of genes, genes code for making proteins)
 DNA wrapped around histones to form Chromatin
 nucleus has a double membrane, called Nuclear Envelope, which contains pores
 at centre of nucleus is Nucleolus – produces mRNA (copy of a gene)
 rest of nucleus made of Nucleoplasm (contains the DNA/chromatin)

Question 3

Endoplasmic Reticulum?

Answer 3

 2 types = Rough and Smooth
 Rough Endoplasmic Reticulum has ribosomes on it, makes proteins
 Smooth Endoplasmic Reticulum has no ribosomes on it, makes lipids/carbohydrates

Question 4

Golgi body?

Answer 4

 modifies and packages proteins and lipids
 packages them into vesicles for transport
 digestive enzymes are placed into lysosomes (vesicles with membranes around them)

Question 5

Mitochondria?

Answer 5

• site of aerobic respiration where ATP is produced
• They have a double membrane
• their inner membrane is folded to form cristae
• inside is the matrix- contains enzymes involved in respiration

Question 6

Ribosomes?

Answer 6

 attached to RER
 site of protein synthesis

Question 7

What is a Plant Cell made of?

Answer 7

 Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, chloroplast, vacuole, ribosomes) – all have membrane except the ribosomes
 Cytoplasm (site of chemical reaction)
 Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)
 Cell Wall (made of cellulose, prevents cell from bursting or shrinking)

Question 8

Structure of chloroplast?

Answer 8

 organelle for photosynthesis
 has double membrane
 contains discs called thylakoids
 thylakoids contain chlorophyll
 stack of thylakoids called granum
 thylakoids surrounded by a fluid called stroma

Question 9

Vacuole?

Answer 9

• Surrounded by a membrane called a tonoplast
• contains Cell Sap (water, sugar, minerals)

Question 10

What is Bacteria made of?

Answer 10

 No nucleus – loose DNA in the form of a single loop and plasmid
 No membrane bound organelles: smaller ribosomes, mesosomes – infolding of cell membrane for respiration
 Cytoplasm
 Cell Membrane & Cell Wall (made of peptidoglycan/murein)
 some have a Capsule (reduce water loss, protect from phagocytosis) and Flagella (movement)

Question 11

What is Virus made of?

Answer 11

 DNA or RNA (if RNA, also has a enzyme called reverse transcriptase to turn RNA into DNA)
 Protein Coat called Capsid and Lipid Coat
 Attachment proteins on outside

Question 12

What is a Chromosome?

Answer 12

 DNA in coiled form
 formed during interphase of cell division (mitosis/meiosis) in Animals/Plants
 made of 2 identical/sister chromatids joined by a centromere
 carries 2 copies of the same DNA molecule

Question 13

What is a homologous pair of chromosomes?

Answer 13

a pair of chromosomes: 1 maternal (from mother)/1 paternal (from father)
carries same genes but different alleles – there are 23 pairs in humans

Question 14

What is Cell Division?

Answer 14

 formation of new cells in multicellular organisms (animals & plants)
 2 methods = mitosis & meiosis
 mitosis = produces genetically identical cells for growth & repair of tissues
 meiosis = produces genetically different haploid cells as gametes for sexual reproduction

Question 15

What does Mitosis (cell cycle) produce?

Answer 15

2 genetically identical cells, diploid (have full set of chromosomes/DNA)

Question 16

Interphase?

Answer 16

G1: protein synthesis
S: DNA replication (doubles set of DNA)
G2: organelle synthesis

Question 17

Mitosis?

Answer 17

• Prophase: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
• Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere
• Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
• Telophase: chromatids uncoil, nucleus reforms (left with 2 genetically identical nuclei)

Question 18

Cytokinesis?

Answer 18

separating cell into 2 (each receives a nucleus and organelles/cytoplasm)

Question 19

What happens to DNA mass in mitosis?

Answer 19

halves

Question 20

What happens to Chromosome number in mitosis?

Answer 20

stays the same (diploid)

Question 21

What is Cancer?

Answer 21

formation of a tumour due to uncontrolled cell division (uncontrolled mitosis)

Question 22

How does uncontrolled cell division occur?

Answer 22

 due to mutation of DNA/cells forming cancer cells
 mutation can occur randomly or due to mutagens (chemicals/radiation)
 cancer cells are rapidly dividing cells (like hair cells, skin cells, red blood cells), they spend less time in interphase and more time in the other stages (mitosis)

Question 23

Treatment for Cancer?

Answer 23

Surgery = aim is to remove tumour

Chemotherapy = - using drugs that inhibit mitosis in rapidly dividing cancer cells
- problem, also affect normal healthy cells (hair cell, skin cells, rbcs) causing side effects (hair loss, dry skin, tiredness)
- treatment given as regular doses to allow time for normal healthy cells to recover in number

Radiotherapy = radiation used to destroy cancer cells

Question 24

How do Bacteria do Cell Division?

Answer 24

 Binary Fission
 Copy their DNA (Single Loop and Plasmids) and then separate into 2 new genetically identical bacteria [Asexual Reproduction]

Question 25

Magnification?

Answer 25

how much larger the image size is compared to the actual size

Question 26

Conversion for magnification?

Answer 26

1 mm = 1000 micrometre.
1 mm = 1,000,000 nanometre

Question 27

Resolution?

Answer 27

minimum distance at which 2 very close objects can be distinguished

Question 28

Why does electron microscopes have a higher resolution?

Answer 28

Electron microscope uses electrons which have a shorter wavelength (light microscope uses light which has a large wavelength)

Question 29

Difference between TEM and SEM?

Answer 29

in Transmission the electrons pass through the specimen
in Scanning the electrons bounce off the specimen’s surface

Question 30

Advantage and Disadvantage of TEM?

Answer 30

 Advantage = highest magnification and highest resolution
 Disadvantage = works in a vacuum so can only observe dead specimens, specimen needs to be thin, black and white image, 2D image, artefacts

Question 31

Advantage and Disadvantage of SEM?

Answer 31

 Advantage = produces 3D image
 Disadvantage = works in a vacuum so can only observe dead specimens, black and white image, artefacts

Question 32

Cell Fractionation?

Answer 32

 Breakdown tissue into cells (cut, pestle & mortar)
 add cold/isotonic/buffer solution (cold = reduce enzyme activity, isotonic = same water potential so organelle does not shrink or burst, buffer = maintains constant pH)
 homogenate – breaks open cells releasing organelles
 filter = removes large debris and intact cells
 centrifuge – spin at low speed, largest organelle builds at bottom (nucleus), leaves supernatant, spin at higher speed, next heaviest organelle forms at bottom (chloroplast or mitochondria)
 (organelle by size: nucleus, chloroplast, mitochondria, endoplasmic reticulum/golgi body/lysosomes, ribosomes)

Question 33

How does a virus infect cells?

Answer 33

• infects host cells by attaching using their attachment protein
• send in their DNA which uses the cell to make the viruses components and uses the cell membrane to make the viruses lipid coat
• producing copies of the virus and destroying the host cell

Question 34

how to calculate the mitotic index?

Answer 34

number of cells with visible chromosomes/ total number of cells observed