B1 cell biology

Question 1

what is a chromosome

Answer 1

The structure made of DNA that codes for all the characteristics of an organism

Question 2

what is a gene

Answer 2

A section of a chromosome that contains the code for the production of a particular protein

Question 3

what is DNA

Answer 3

The material inside the nucleus of cells, carrying the genetic information of a living being.

Question 4

female chromosomes

Answer 4

both identical (XX)

Question 5

male chromosomes

Answer 5

different (XY)

Question 6

when do cells divide?

Answer 6

. when an organism grows
. when an organism becomes damaged and needs to produce new cells

Question 7

what is DNA synthesis

Answer 7

the chromosomes becoming double stranded

Question 8

the stages of the cell cycle

Answer 8

. cell grows
. DNA synthesis
. further growth occurs + DNA checked for errors
. Mitosis
. cytoplasm seperates - two cells formed
. temporary resting period (the cell stops dividing)

Question 9

what is produced from mitosis

Answer 9

two identical daughter cells

Question 10

electron vs light microscopes

Answer 10

light:
cheaper, lower resolution, lower magnification
electron:
more expensive, higher resolution, higher magnification

Question 11

equation to find magnification

Answer 11

magnification = image size/real size

Question 12

steps to prepare a slide (RP)

Answer 12

. add a drop of water to the middle of a clean slide
. cut up a specemin (eg onion) and use tweezers to place the tissue onto the slide
. add a drop of stain (iodine solution)
. place a cover slip on top

Question 13

using a light microscope to view a slide (RP)

Answer 13

. clip the prepared slide onto the stage
. select the lowest powered objective lens
. use the coarse adjustment knob to move the stage up to just below the objective lens
. look down the eyepiece. use coarse adjustment knob to move stage downwards until image is roughly in focus
. adjust the focus with the fine adjustment knob until you get a clear image
. if you need greater magnification, swap to a higher powered objective lens and refocus

Question 14

define cell differentiation

Answer 14

the process by which cells become specialised for a specific function

Question 15

how are sperm cells specialised for reproduction

Answer 15

long tail and streamlined head to help it swim to the egg
lots of mitochondria to provide the energy needed
carries enzymes to digest thjrough the egg cell membrane

Question 16

how are nerve cells specialised for rapid signalling

Answer 16

long to cover more distance
branched connections to form a network throughout the body

Question 17

how are muscle cells specialised for contraction

Answer 17

long so they have space to contract
lots of mitochondria to generate the energy needed for contraction

Question 18

how are root hair cells specialised

Answer 18

large surface area for absorbing water and mineral ions from the soil
high concentrations of mitochondria for energy needed for active transport

Question 19

what do phloem cells transport and how are they specialised

Answer 19

transports food. joined end to end, very few sub-cellular structures so more can flow through them

Question 20

what do xylem cells transport and how are they specialised

Answer 20

water. joined end to end, hollow in the centre

Question 21

risks of using stem cells in medicine

Answer 21

cells grown in the lab may become infected with a virus which could be passed on to the patient.
rejection

Question 22

therapeutic cloning

Answer 22

an embryo being made to have the same genetic information as the patient. would avoid rejection

Question 23

reasons why people are against stem cell research in embryos

Answer 23

. stem cells shouldn’t be used in research as each one is a potential human life
. stem cell research is banned in some countries
. scientists should concentrate more on finding/developing alternative methods of stem cells that don’t use embryos

Question 24

diffusion definition

Answer 24

the spreading out of particles from an area of higher concentration to an area of lower concentration
with the concentration gradient - no energy

Question 25

osmosis definition

Answer 25

the movement of watre molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
with the concentration gradient - no energy

Question 26

active transport

Answer 26

the movement of substances against a concentration gradient, requires energy, lower to higher concentration.

Question 27

how to find surface area : volume ratio

Answer 27

find total surface area, find volume, simplify the ratio

Question 28

trend for surface area : volume ratio

Answer 28

the larger an organism is, the smaller the surface area: volume ratio

Question 29

general adaptations of exchange surfaces

Answer 29

thin membrane so substances have a short diffusion pathway
large surface area so more of a substance can diffuse at once
exchange surfaces are often ventilated