B1 - Cell biology

Question 1

Cells:
What are eukaryotic cells?

Answer 1

Complex cells - animal and plant cells

Question 2

Cells:
What are prokaryotic cells?

Answer 2

Smaller + simpler - bacteria

Question 3

Cells:
What is a eukaryote?

Answer 3

Organisms made of eukaryotic cells

Question 4

Cells:
What is a prokaryote?

Answer 4

Single celled organism eg prokaryotic cells (bacteria)

Question 5

Cells:
What are the sub cellular structures of an animal cell?

Answer 5

• Nucleus - DNA + cell activities
• Cytoplasm - chemical reactions occur + contain enzymes (control the chemical reactions)
• Cell membrane - controls in and out of cell
• Mitochondria - aerobic respiration (transfers energy cells needs to work)
• Ribosomes - site of protein synthesis

Question 6

Cells:
What are the sub cellular structures in a plant cell?

Answer 6

• Nucleus, Cytoplasm, Cell membrane, Mitochondria, Ribosomes
• Cell wall - made of cellulose + support/ strengthen cell
• Permanent vacuole - cell sap (weak solution sugars + salts)
• Chloroplasts - photosynthesis occurs + contain chlorophyll

Question 7

Microscopy -
What do light microscopes used?

Answer 7

Light + lenses form image of specimen + magnify

Question 8

Microscopy -
What can you see using a light microscope.

Answer 8

Individual cells, large sub cellular structure (eg nuclei)

Question 9

Microscopy -
What does an electron microscope use?

Answer 9

Electrons to form image

Question 10

Microscopy -
What is the difference between an electron microscope and a light microscope?

Answer 10

Electron microscopes have:
- higher magnification
- higher resolution (ability to distinguish between two objects )
- can see smaller things in more detail (eg mitochondria, chloroplasts, plasmids, ribosomes)

Question 11

Microscopy -
What is the equation for magnification?

Answer 11

Magnification = image size/ real size

Question 12

Microscopy - RP
How do you prepare a slide?

Answer 12

1. Drop water to clean slide
2. Cut onion + separate layers use tweezers peel epidermal tissue (bottom layer)
3. Use tweezers place epidermal tissues into water on slide
4. Drop iodine solution (stain + highlight cells by adding colour)
5. Cover slip on top (no air bubbles)

Question 13

Microscopy - RP
How to use a light microscope to look at your slide?

Answer 13

• clip slide onto stage
• lowest powered objective les (lowest magnification)
• coarse adjustment know move stage below objective lens
• look down eyepiece + coarse adjustment known move stage down until image roughly focused
• adjust focus fine adjustment know until clear image
• if need see in greater magnification swap to higher powered objective lens and refocus

Question 14

Cell Differentiation and specialisation:
What is differentiation?

Answer 14

Process by which cells change + become specialised for its job.

Question 15

Cell Differentiation and specialisation:
What happens as the cells change during differentiation?

Answer 15

different sub cellular structures + turn different types of cells (carry out specific functions)

Question 16

Cell Differentiation and specialisation:
When does most differentiation occur in an organism?

Answer 16

As it develops

Animals cells - ability lost in early stage (after become specialised)
Plant cells - don’t lose ability

Question 17

Cell Differentiation and specialisation:
What are the cells that differentiate in mature animals mainly used for?

Answer 17

Repair and replacing cells (skin and blood cells)

Question 18

Cell Differentiation and specialisation:
What are a type of cell that are undifferentiated?

Answer 18

Stem cells

Question 19

Cell Differentiation and specialisation:
What are examples of specialised cells and how that are specialised for certain function?

Answer 19

1. Sperm cells - reproduction (get male
   DNA to female DNA in egg cell): long tail + streamline (swim to egg), lots mitochondria (energy), enzymes in acrosome (head) digest egg cell membrane.
2. Nerve cells - rapid signalling (carry electrical signals from one part of body to other - distance), branched connections at ends of other nerve cells + form network.
3. Muscle cells - contraction (contract quickly), long (space to contract), lots mitochondria for energy needed to contract
4. Root hair cells - absorbing water + mineral ions (surface of plant roots), plant large surface area for absorption.
5. Phloem + xylem cells - transporting substances (form phloem + xylem tubes transport food and water around plant), long + joined end to end. Xylem -hollow, phloem few sub-cellular structure so food flow.

Question 20

Chromosomes and Mitosis:
What do chromosomes contain?

Answer 20

Genetic information

Question 21

Chromosomes and Mitosis:
Where are your chromosomes contained?

Answer 21

Nucleus

Question 22

Chromosomes and Mitosis:
What are chromosomes?

Answer 22

Coiled up lengths of DNA molecules

Question 23

Chromosomes and Mitosis:
What do each chromosome carry?

Answer 23

Genes

Question 24

Chromosomes and Mitosis:
What do different genes control?

Answer 24

The development of different characteristics

Question 25

Chromosomes and Mitosis: How many copies of each chromosome do body cells have?

Answer 25

Two (one father, one mother)

Question 26

Chromosomes and Mitosis: How many pairs of chronometer do human cells have?

Answer 26

23 (46 in total)

Question 27

Chromosomes and Mitosis: What is the cell cycle?

Answer 27

Where body cells in multicellular organisms divide to produce new cells

Question 28

Chromosomes and Mitosis: What is the stage of the cell cycle when the cell divides called?

Answer 28

Mitosis

Question 29

Chromosomes and Mitosis: What do multicellular organisms use mitosis for?

Answer 29

Growth and replacement of damaged cells

Question 30

Chromosomes and Mitosis: What does the end of the cell cycle result in?

Answer 30

Two new identical cells to the original cell (same number of chromosomes)

Question 31

Chromosomes and Mitosis: What happens in the state of the cell cycle of Growth and DNA replication?

Answer 31

1. Cells not dividing - DNA spread in long strings 2. Before divides, cell grow and increase sub cellular structures eg mitochondria and ribosomes 3. Duplicated DNA - one copy for each cell (form X shaped chromosomes + each arm of chromosome is an exact duplicate of the other. (Left + right arm same DNA)

Question 32

Chromosomes and Mitosis: What happens in the stage of the cell cycle called mitosis?

Answer 32

Once content + DNA copied, cell ready for mitosis. 1. Chromosomes lien up at centres cell + cell fibres pull them apart. Two arms each chromosome go to opposite ends of cell. 2. Membranes form around chromosomes (become nuclei of two new cells - nucleus divided) 3. Cytoplasm + cell membrane divide 4. Produced two identical daughter cells (DNA identical to each other and parent cells)

Question 33

Binary Fission: What type of cells replicate by binary fission?

Answer 33

Prokaryotic cells

Question 34

Binary Fission: What happens during binary fission?

Answer 34

1. Circular DNA + plasmids replicate 2. Cell get bigger + DNA to opposite poles of cell 3. Cytoplasm begins to divide + new cell wall being form 4. Cytoplasm divides + two daughter cells produced (each daughter cell one copy circular DNA but variable number of plasmids)

Question 35

Binary Fission: What conditions do bacteria need to divide very quickly?

Answer 35

- warm environment - lots of nutrients

Question 36

Binary Fission: How long do bacteria such as E Coli take to replicate in right environment?

Answer 36

20 minutes

Question 37

Binary Fission: What happens to bacteria if the conditions become unfavourable?

Answer 37

Stop dividing + eventually die

Question 39

Culturing Microorganisms: RP What are bacteria grown in?

Answer 39

A culture medium

Question 40

Culturing Microorganisms: RP What does a culture medium contain?

Answer 40

- carbohydrates - minerals - proteins - vitamins That they need to grow

Question 41

Culturing Microorganisms: RP What are the two culture mediums that can be used?

Answer 41

- nutrient broth solution - agar jelly

Question 42

Culturing Microorganisms: RP How do you make an agar plate?

Answer 42

1. hot agar jelly poured into Petri dish 2. Agar jelly cooled + set - inoculating loop transfer microorganisms to culture medium. 3. Microorganisms multiply

Question 43

Culturing Microorganisms: RP What temperature are the cultures of microorganisms kept in a lab + why?

Answer 43

Not above 25 degrees celcius - because harmful pathogens more likely to grow at higher temperatures.

Question 44

Culturing Microorganisms: RP Why are cultures incubated at higher temperature in industrial conditions?

Answer 44

Grow a lot faster

Question 45

Culturing Microorganisms: RP

Question 46

Culturing Microorganisms: RP How do you test the action of antibiotics/ antiseptics on cultures of bacteria - method?

Answer 46

1. Plastic discs soaked in different types/ concentrations of antibiotics on nagar plate. (some space between discs) 2. Antibiotics diffuse into agar jelly - antibiotic resistant bacteria no affected will grow on agar around discs + non resistant strains die (create inhibition zone around discs) 3. Use paper discs not soaked in antibiotic (as control) 4. Leave plate for 48 hours at 25 degrees Celsius 5. More effective antibiotic = larger inhibition zone

Question 47

Culturing Microorganisms: RP What will affect your results + potentially result in?

Answer 47

- Contamination by unwanted microorganisms - potential result in growth of pathogens

Question 48

Culturing Microorganisms: RP How can you avoid contamination?

Answer 48

- Petri dish + culture medium sterilised (kill unwanted microorganisms) - Inoculating loop - sterilised (pass through blue flame) - Lid Petri dish lightly tape (stop microorganisms from air getting in) - Petri dish stored upside down (stop condensation drops falling to agar surface)

Question 49

Culturing Microorganisms: RP How do you calculate the size of inhibition zone to compare results?

Answer 49

- measure the diameter of inhibition zone to calculate it's area (larger the inhibition zone, the more effective the antibiotic is against the bacteria)

Question 50

Culturing Microorganisms: RP How do you calculate the area of a colony?

Answer 50

-measure the diameter of the colony and then calculate the area.

Question 51

Stem Cells - What is a stem cell an example of?

Answer 51

An undifferentiated cell (can differentiate into different types of cell depending on their instructions)

Question 52

Stem Cells - What can embryonic stem cells turn into and where are they found?

Answer 52

- found into early human embryos - ability to turn into any type of cell

Question 53

Stem Cells - Where are stem cells found in adults?

Answer 53

- bone marrow

Question 54

Stem Cells - What is the difference between embryonic and adult stem cells?

Answer 54

-Embryonic stem cells can become any type of cell - Adult stem cells can't turn into any type of cell (only come such as blood cells)

Question 55

Stem Cells - What can embryonic and adult stem cells be grown in a lab to produce?

Answer 55

-Clones (genetically identical cells) made to differentiate into specialised cells to be used in medicine and research

Question 56

Stem Cells - What do medicine use adult stem cells to do and example?

Answer 56

- Cure disease Example: Bone marrow from healthy person can replace faulty blood cells in patient who receives them)

Question 57

Stem Cells - What can embryonic stem cells also be used to do and examples?

Answer 57

- replace faulty cells in sick people Examples: - Make insulin - producing cells for people with diabetes - Make nerve cells for people paralysed by spinal injuries

Question 58

Stem Cells - What is therapeutic cloning?

Answer 58

Embryo made have same genetic info as patient (mean wouldn't be rejected by patients body if used to replace faulty cells)

Question 59

Stem Cells - What are the risks involved with using stem cells in medicine?

Answer 59

- stem cells grown in lab be contaminated by virus (passed onto patient and make them more ill)

Question 60

Stem Cells - What are the for and against arguments for stem cell research? ?

Answer 60

- human embryos are potential human life + curing people suffering more important than the rights of embryos (argue embryos used usually unwanted so would just be destroyed anyway) - campaigners for rights of embryos feel scientists come up with other sources of stem cells - some countries stem cells research banned (allowed in UK as long as under strict guidelines)

Question 61

Stem Cells - Where are stem cells found in plants?

Answer 61

Meristems (part of plant where grow occurs)

Question 62

Stem Cells - How long can meristem tissue differentiate into any type of plant cell?

Answer 62

Entire life

Question 63

Stem Cells - What are stem cells found in meristem tissue used to produce and why?

Answer 63

- clones (cheaply and quickly) - grow rare species (prevent extinction) - grow identical plants with desired features for farmers (eg disease resistant)

Question 64

Diffusion - What is diffusion?

Answer 64

The spreading out of particles from an area of higher concentration to an area of lower concentration

Question 65

Diffusion - In what substances does diffusion occur and why?

Answer 65

-solutions - gases Because particles free to move about randomly

Question 66

Diffusion - What causes a faster rate of diffusion?

Answer 66

- bigger concentration gradient - higher temperature (particles more energy to move so faster)

Question 67

Diffusion - What type of molecules can diffuse through cell membrane and examples:

Answer 67

very small molecules eg oxygen, glucose, amino acids, water

Question 68

Diffusion - What type of molecules can't diffuse through cell membranes and examples:

Answer 68

big molecules eg starch, protein (can't fit through membrane)

Question 69

Diffusion - What direction do particles diffuse across a cell membrane and what does this cause?

Answer 69

- both ways - means if a lot more particles on one side of membrane, net (overall) movement from that side

Question 70

Diffusion - What causes a faster rate of diffusion across a cell membrane?

Answer 70

- larger surface area of the membrane (more particles can pass through at once)

Question 71

Osmosis - What is osmosis?

Answer 71

The movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration.

Question 72

Osmosis - What does a partially permeable membrane mean?

Answer 72

- membrane with very small holes in it (only tiny molecules eg water can pass through and bigger molecules eg sucrose can't)

Question 73

Osmosis - What direction do water molecules pass through the membrane during osmosis and why?

Answer 73

Both ways - water molecules move randomly constantly (but more water molecules on one side meas there's a steady net flow)

Question 74

Osmosis - What is osmosis a type of?

Answer 74

Diffusion (passive movement of water molecules from higher to lower concentration)

Question 75

Osmosis - RP Method:

Answer 75

1. cut potato into identical cylinders + beakers with different sugar solution (one pure water, one very concentrated sugar solution (1.0 mol/dm cubed) and few other concentrations in between (0.2, 0.4, 0.6) 2. measure mass of cylinders using top pan balance + leave in beaker for 24 hours 3. Take cylinders out + dry with paper towel + measure masses again 4. Increase in mass if water drawn in by osmosis, decrease in mass if water drawns out by osmosis. 5. Calculate percentage change in mass + plot graphs to compare effect of sugar concentrations on cylinders with same initial mass. (increase in mass mean positive percentage change) 6. Dependent variable = potato mass Independent variable = conc of sugar solution Control variables = volume solution, temp, time, type of sugar 7. Errors that could occur = - not fully dried cylinders mean excess water give higher mass - water evaporated from beaker mean conc of sugar solutions change 8. Repeat experiment and calculate mean percentage change at each conc (can also use different concs of salt solutions)

Question 76

Active Transport - What is active transport?

Answer 76

The movement of substances from a lower conc to a higher conc against the concentration gradient which requires energy.

Question 77

Active Transport - How is active transport used in plants?

Answer 77

For root hair cells to take in water and mineral ions - root hair cells mean large surface area for absorption on water and mineral ions from the soil - need for health growth - conc mineral usually higher in root hair cell than coil - root hair cell can't use diffusion so uses active transport to absorb water and mineral ions - root hair cells use osmosis for absorption of water

Question 78

Active Transport - What does active transport allow plants to absorb minerals from?

Answer 78

A very dilute solution against the conc gradient (essential for growth)

Question 79

Active Transport - What does active transport need?

Answer 79

Energy from respiration to work

Question 80

Active Transport - Where does active transport occur in humans?

Answer 80

Used in gut when there's lower conc of nutrients in the gut and higher conc of nutrients in blood

Question 81

Active Transport - What does active transport mean for glucose being taken into the bloodstream?

Answer 81

Can be taken into bloodstream if conc of glucose in blood higher than gut and be transported to cells for respiration

Question 82

Exchange Surfaces - What can cells use diffusion to do and examples:

Answer 82

Take in substances they need + get rid of waste products Examples: - oxygen + carbon dioxide transferred between cells + environment during gas exchange - urea (waste from breakdown of proteins) diffuses from cells to blood plasma for removal from body by kidneys

Question 83

Exchange Surfaces - What does the ease at which an organism can exchange substances with the environment depend on?

Answer 83

Organisms surface area to volume ratio

Question 84

Exchange Surfaces - The larger an organism is

Answer 84

the smaller its surface area to volume ratio

Question 85

Exchange Surfaces - How do you calculate volume?

Answer 85

length x width x height

Question 86

Exchange Surfaces - Which organism would have a higher surface area to volume ratio, a hippo or a mouse?

Answer 86

Mouse

Question 87

Exchange Surfaces - In single celled organisms, why can dissolved substances + gases diffuse directly into/ out of cell across the membrane?

Answer 87

- large surface are to volume ratio (mean enough substances can exchange cross membrane + supply volume of cell

Question 88

Exchange Surfaces - What does a multicelluar organism having a smaller surface area to volume ratio mean?

Answer 88

- not enough substances diffuse from their outside surface to supply their entire volume

Question 89

Exchange Surfaces - What does a multicellular organism have to have because of their smaller surface area to volume ratio?

Answer 89

Exchange surfaces for efficient diffusion

Question 90

Exchange Surfaces - How are exchange surfaces adapted to maximise effectiveness?

Answer 90

- thin membrane (short diffusion pathway) - large surface area (lots of substances can diffuse at once) - in animals have lots of blood vessels (substances into and out of the blood quickly) - gas exchange surfaces in animals ventilated eg alveoli (air move in and out)

Question 91

Exchange Substances - What is the job of the lungs?

Answer 91

Transfer oxygen to blood and remove waste carbon dioxide from blood

Question 92

Exchange Substances - What do the lungs contain millions of in order to carry out their function?

Answer 92

Alveoli where gas exchange takes place

Question 93

Exchange Substances - How are the alveoli adapted to maximise diffusion?

Answer 93

- large surface area - moist lining (for dissolving gases) - thin walls - good blood supply

Question 94

Exchange Substances - What is the inside of the small intestine covered in?

Answer 94

Millions of villi

Question 95

Exchange Substances - What do villi to mean digested food is absorbed faster into the blood?

Answer 95

Increase the surface area

Question 96

Exchange Substances - What do villi have?

Answer 96

- single layer of surface cells - blood blood supply to assist fast absorption

Question 97

Exchange Substances - How does the structure of a leaf let gases diffuse in and out of cells?

Answer 97

1. CO2 diffuses into air spaces within leaf 2. CO2 diffuses into cells where photosynthesis occurs (leaf structure adapated so happens easily) 3. Underneath of leaf is exchange surface and covered in stomata which CO2 diffuses in through 4. oxygen + water vapour diffuses out through stomata (water vapour lost from all over leaf surface as well as stomata) 5. size stomata controlled by guard cells (close stomata if losing water faster than being replaced by roots) 6. flattened shape of leaf increase area of exchange surface 7. walls of cells in leaf form another exchange surface 8. air sacs in leaf increase area of surface so CO2 get into cell more easily

Question 98

Exchange Substances - What is the underneath of a leaf covered in and what substance diffuses in and out of them?

Answer 98

Stomata CO2 = in O2 + water = out

Question 99

Exchange Substances - What is the size of the stomata controlled by?

Answer 99

Guard cells

Question 100

Exchange Substances - What would happen to the plant if there were no guard cells?

Answer 100

Wilt

Question 101

Exchange Substances - What is an example of an exchange surface in fish?

Answer 101

Gills

Question 102

Exchange Substances - Process of gas exchange in fish:

Answer 102

1. water (containing oxygen) enter fish through mouth + pass through gills 2. As this occurs, oxygen diffuses from water to blood in gills and CO2 diffuses from blood to water 3.

Question 103

Exchange Substances - What is each gill made of and purpose?

Answer 103

lamellae which increase surface area

Question 104

Exchange Substances - What do lamellae have lots of to speed up rate of diffusion?

Answer 104

- lots of blood capillaries - thin surface layer (minimise distance gases have to diffuse)