Revision for September Flashcards
How does each colony of bacteria grow?
through cell division
Why is it important to sterilise apparatus before use?
to prevent contamination in order to prevent other organisms from affecting the results
Why are Petri dishes incubated at 25 degrees celsius at school?
to prevent the growth of pathogens
Why would an investigation be repeated?
to improve the reliability of the investigation
to check for anomolies
Key features of asexual reproduction:
requires only one parent
parent produces genetically identical clones of itself
no mixing of genetic material
in this type of reproduction, body cells divide by mitosis
what are the male + female chromosomes?
female: 2X chromosomes
male: 1X 1Y chromosomes
Why use stem cells?
stem cells can differentiate
stem cells can divide
what are the uses of stem cells?
medical research, medical treatment
Why may people reject use of Stem cells from embryos?
it is unethical, religious reasons, could cause harm to embryos
Why do human skin cells need to divide?
for growth + repair
Human stem cells can treat…
paralysis
Process of mitosis:
DNA replicates to form 2 copies of each chromosome
the cell grows and copies its internal structures
one set of chromosomes is pulled to each end of the dividing cell + the nucleus divides
the cytoplasm + cell membrane divides to form 2 identical daughter cells
How do prokaryotic organisms undergo cell division?
binary fission
Why would cell division stop?
shortage of nutrients
so cells die
Why can an immature egg not be used to produce a baby?
egg only contains the genetic information of the mother
it’s asexual as there is no sperm involved
ethical/moral/religious issues
cells used to treat disease cannot later be used to produce a baby
Why do most organisms have an even number of chromosomes?
chromosomes come in pairs
organisms inherit one of each pair form each parent
What substances do plants absorb by active transport?
minerals
ions
Describe the function of muscle cells in the wall of the stomach.
to contract
to churn food
Function of mitochondira:
to transfer energy for use
by respiration
Describe how a student should prepare an uncontaminated culture of a bacterium in a Petri dish.
Sterilise the Petri dish and agar plate before use.
This kills any unwanted bacteria and prevents contamination.
Then pass the inoculating loop through a Bunsen burner flame to sterilise it.
Next, keep the lid of the Petri dish open as little as possible and spread the bacterium onto the agar plate using the inoculating loop.
This is to prevent microbes from the air entering and contaminating the agar plate.
Then seal the lid of the Petri dish using tape, which prevents it from falling off and allowing microbes to enter from the air.
Finally, incubate the agar plate to allow for the growth of bacteria.
What are the areas in which bacteria have not grown on an agar plate called?
zone of inhibition
How can a vaccine limit the number of people with a virus?
can provide immunity
can prevent virus from spreading
Explain why single-celled organisms, like algae, do not need complex structures for gas exchange.
cell has a larger surface area to volume ratio
cell has a short diffusion distance
diffusion via cell membrane is good enough
what does the xylem transport?
water
minerals/ions
What does the phloem transport?
sugar
What is translocation?
the movement of dissolved sugars
Explain why translocation is important to plants.
sugars are made in the leaves
need to be transported to the rest of the plant
for growth or storage
Explain why active transport is necessary in root hair cells.
for movement of minerals/ions
against the concentration gradient
Explain the advantages of red blood cells passing through a capillary one at a time.
more oxygen released to tissue
slows the flow
more surface area is exposed
Methods to prevent contamination:
sterilise
work near a flame
minimise the opening of apparatus
pass apparatus mouth through a flame
Describe the pathway taken by the nerve impulse in the blink reflex.
from the light sensitive cell to the sensory neurone
sensory neurone to brain
brain to motor neurone
motor neurone to muscle (effector)
Why do plants need starch?
to store energy
Explain how oxygen passes from the blood to the mitochondira
diffusion
from high to low concentration
through cytoplasm or cell membrane
Enzyme are…
proteins
Describe how the ribosomes and mitochondria help the cell to make enzymes.
ribosomes make proteins
using amino acids
mitochondria provide energy for this process
Oxygen is carried in the blood in…
red blood cells
What is diffusion?
the movement of particles
from high to low concentration
Carbohydrates are broken down by..
carbohydrase or amylase
proteins are broken down by… into…
protease enzymes
into amino acids
starch is broken down by… into…
amalyse
glucose molecule chains are turned into simple sugars
lips are broken down by… into
lipase
into 1 molecule of glycerol + 3 molecules of fatty acids
Why may the concentration of glucose in the small intestines decrease?
absorption of glucose
into the bloodstream
by active transport
Function of stomata:
control water loss
carbon dioxide in, oxygen out
Adaptations of the lungs that help the rapid absorption of oxygen into the blood:
large surface area
lots of alveoli
good blood supply
short diffusion pathway
Why use blotting paper?
to remove solution
How might the method of blotting cause errors in results?
variable amounts removed from each
Describe how water moves from roots to the leaves.
by a transpiration stream
in the xylem
How might a student collect data on the number of stomata on a leaf?
mount epidermis onto a slide
count the number of stomata on one side
repeat on the other side of the leaf
calculate a mean
Why is having fewer stomata on the upper surface of the leaf an advantage?
less water loss
so plant doesn’t wilt
Describe how glucose from the small intestine is moved to a muscle cell.
glucose is absorbed by diffusion into the bloodstream
the blood delivers glucose to muscles in capillaries
Compare anaerobic respiration in a yeast cell with anaerobic respiration in a muscle cell.
yeast cells produce ethanol whereas muscle cells produce lactic acid
yeast cells release carbon dioxide, but muscle cells don’t
both release a small amount of energy
Describe how information passes from the relay neurone to the motor neurone.
electric impulses trigger synaptic vesicles to start moving + bind to the end of dendrites
where they release a chemical (neurotransmitter)
to diffuse across the synapse
and bind to the receptor site of the next neurone
What is hypertonic?
outside the cell is more concentrated
than inside the cell
What is hypotonic?
inside the cell is more concentrated
than outside the cell
plant cells in a hypotonic solution?
turgid
plant cells in a hypertonic solution?
plasmolysed
