B1: Cell Biology

Question 1

What is the difference between EUKARYOTIC & PROKARYOTIC cells?

Answer 1

● Eukaryotic Cells group together to form multicellular organisms, contain a Nucleus, Mitochondria and can contain chloroplasts.
● Prokaryotic Cells form single-celled organisms, such as bacteria, and do not have a Nucleus, Mitochondria or chloroplasts.

Question 2

What are the organelles in an animal cell and their function?

Answer 2

● Nucleus: Contains the Genetic Material & controls the Cell
● Cell membrane: Controls what enters & leaves the cell
● Cytoplasm: Is where most metabolic reactions occur
● Mitochondria: Contain the enzymes required for aerobic respiration
● Ribosomes: Synthesise proteins

Question 3

What are the plant-specific organelles and their function?

Answer 3

● Chloroplasts: Trap energy from sunlight for use in photosynthesis
● Permanent Vacuole: Hold Cell sap in the cell, which is a combination of sugars & salts
● Cell Wall: Gives structure & shape to the cell

Question 4

What are the organelles in a Bacterial cell and their function?

Answer 4

○ Bacteria cells have a cell wall, cell membrane, cytoplasm as well as…
● Circular chromosomal DNA: A loop of Genetic material that replaces the nucleus
● Plasmids: Small rings of DNA that can be interchanged between bacteria to evolve
● Flagella: A whip-like structure used for propulsion

Question 5

What is cell specialisation?

Answer 5

Cell Specialisation is when an undifferentiated cell activates certain genes, takes on a new shape and develops new organelles to perform a specific function.

Question 6

How is a sperm cell specialised?

Answer 6

● They have a streamlined shape
● They have a tail (flagellum) for propulsion
● They have lots of mitochondria for swimming (stored in the middle section)
● They have digestive Enzymes (Acrosomes) in the head to penetrate the egg & fertilise it
● They contain only one half of genetic material

Question 7

How is a Neurone Specialised?

Answer 7

● It has a long axon to carry electrical signals over long distances
● It has many dendrites & branches to form connections with other neurones
● Its axon is covered in an insulating sheath made of myelin, which speeds up electrical signals

Question 8

How is a muscle cell specialised?

Answer 8

● Consists of protein fibres that can contract

● Contains lots of Mitochondria for the energy to contract

Question 9

How is a Root Hair Cell specialised?

Answer 9

● Has a High Surface area via long projections

● Lots of Mitochondria for active transport, so that Water & Mineral ions can be taken into the plant

Question 10

What are the applications of Stem Cells?

Answer 10

● Therapeutic cloning
↳ An adult nucleus is implanted into hollow embryonic stem cells and allowed to increase in size.
↳ These cells can them differentiate into any cell required for treatment
● Plant Cloning
↳ Protect Rare species
↳ Modify existing crops for high yield
● Stem Cell treatment
↳ extracted stem cells are stimulated in areas of damage to produce new, healthy cells

Question 11

What are the disadvantages of Stem Cells?

Answer 11

● Ethical Issues: Some believe life begins at conception, and that using embryonic cells is ‘killing’ the embryo
● Viruses can be transferred to patients if the stem cells are infected

Question 12

What is the difference between a light microscope & and electron microscope?

Answer 12

● Light Microscope
↳ Cheap
↳ School Use
↳ Max magnification of x1500
● Electron Microscope
↳ Extremely Expensive
↳ Max magnification of x2,000,000
↳ Highest Resolution

Question 13

What is the equation for magnification?

Answer 13

Image Size = Actual Size x Magnification

I = A x M

Question 14

By what process do Eukaryotic cells Asexually reproduce? How is it done?

Answer 14

● Eukaryotic Cells reproduce via Mitosis, where the cell divides into two identical daughter cells
↳ First, the Cell doubles all its DNA, Mitochondria, Ribosomes and other critical organelles
↳ The Chromosomes are then pulled apart to opposite sides of the cell
↳ Finally, the cell divides, producing cytoplasm & cell membrane to complete the cell structure

Question 15

What is the difference between diffusion, Osmosis & Active Transport?

Answer 15

○ Diffusion
● Random particle movement
● High to Low concentration
● Passive
○ Active Transport
● Requires energy (from respiration)
● Low to High Concentration
● Through a unique Protein in the cell membrane
○ Osmosis
● Through a partially permeable membrane
● Water moves from a dilute solution to a more concentrated one

Question 16

What are some factors that affect the rate of diffusion?

Answer 16

● Temperature
● The distance across which particles have to travel
● The concentration gradient (differences between concentration)
● The Surface Area:Volume Ratio
↳ Surface Area
↳ Particle Size
● Medium of diffusion (i.e. Gas, liquid, solid)

Question 17

How is the small intestine adapted for Diffusion?

Answer 17

○ Small Intestine: Villi
● Large Capillary network to maintain con. Gradient
● One cell thick walls to reduce diffusion distance
● Many folds & projections to increase Surface area

Question 18

How are Gills and Lungs adapted for transportation?

Answer 18

○ Gills
↳ Constant movement through water maintains con. gradient
↳ Folds increase surface area
↳ Thin membrane to reduce diffusion distance
↳ Blood Flow maintains con. gradient
○ Lungs
↳ Constant Breathing maintains con. gradient
↳ Alveoli increase surface area
↳ Walls of alveoli are one cell thick to reduce diffusion distance
↳ Capillary Blood Flow maintains con. gradient

Question 19

How are roots & leaves adapted for transportation?

Answer 19

+ Roots
> Roots have long projections to increase surface area
> Transpiration occurs to maintain a steep concentration gradient between water & mineral ions
+ Leaves
> Stomata ventilate the Spongy Mesophyll maintaining the concentration gradient of carbon dioxide & oxygen
> Transpiration ensures there is always an abundance of water for photosynthesis
> Leaves have a large surface area and there are many of them to maximise photosynthesis

Question 20

How do cells respond when placed in solutions of different concentrations, in terms of Osmosis?

Answer 20

1a = 1 arbitrary unit of concentration of molecule
● When a cell of 5a is placed in a solution of 5a, water enters and leaves the cells in equal amounts
● When a cell of 5a is placed in a solution of 50a, water leaves the cell to dilute the solution, causing the cell to shrivel
● When a cell of 5a is places in a solution of 0.1a, water enters the cell to dilute it, causing the cell to swell up

Question 21

Where does Active transport occur in animals & Plants?

Answer 21

○ Plants
> In the roots, where the root hair cells absorb the mineral ions from the soil
+ Animals
> In the gut, where the intestinal cells absorb soluble food molecules such as sugars & salts

Question 22

-O- How is the growth & cultivation of microorganisms in a laboratory controlled?

Answer 22

+ Bacteria are grown using a culture medium, which can be either a nutrient broth solution or agar jelly.
> These contain the necessary carbohydrates, minerals, proteins & vitamins required for them to grow
> Bacteria on ‘Agar plates’ will form evenly spread visible colonies
+ Bacteria cultures are not kept above 25 degrees celsius within schools as dangerous pathogens grow rapidly above this temperature
> They are incubated at higher temps in industrial settings