cell biology Flashcards
What are the two types of cells?
Eukaryotic (plant and animal)
● Prokaryotic (bacteria)
What are the differences between eukaryotic and
prokaryotic cells?
Prokaryotic cells are much smaller than
eukaryotic cells.
Eukaryotic cells contain membrane
bound-organelles and a nucleus containing
genetic material, while prokaryotes do not.
What are plasmids
Small, circular loops of DNA found free in the
cytoplasm and separate from the main DNA.
● Carry genes that provide genetic advantages
e.g. antibiotic resistance.
How is genetic information stored in a
prokaryotic cell?
Found free within the cytoplasm as:
● Chromosomal DNA (single large loop of circular DNA)
● Plasmid DNA
What is order of magnitude?
A power to the base 10 used to quantify
and compare size
What is a centimetre (cm)?
1 x 10^-2 metres
What is a millimetre (mm)?
1 × 10^-3 metres
What is a micrometre (µm)?
1 × 10^-6 metres
What is a nanometre (nm)?
1 x 10^-9 metres
What is the difference in order of magnitude between
a human hair (length = 100 µm) and the HIV virus
(length = 100 nm)?
100 µm = 10-4 m
100 nm = 10-7 m
-4-(-7) = -4 + 7 = 3
List the components of both plant and animal cells
Nucleus
● Cytoplasm
● Cell membrane
● Mitochondria
● Ribosomes
List the additional cell components found in plant
cells
Chloroplasts
● Permanent vacuole
● Cell wall
Other than storing genetic information, what is the
function of the nucleus?
Controls cellular activities
Describe the structure of the cytoplasm
● Fluid component of the cell.
● Contains organelles, enzymes and dissolved
ions and nutrients.
What is the function of the cytoplasm?
Site of cellular reactions e.g. first stage
of respiration.
Transport medium
What is the function of the mitochondria?
Site of aerobic respiration
in which ATP is produced.
What is the function of the cell membrane?
Controls the entry and exit of materials
into and out of the cell.
What does the permanent vacuole contain?
Cell sap (a solution of salts, sugars and
organic acids).
What is the function of the ribosomes?
Joins amino acids in a specific order
during translation for the synthesis of
proteins.
What is the function of the plant cell wall?
● Provides strength.
● Prevents the cell bursting when water
enters by osmosis.
What is the plant cell wall made of?
Cellulose
What is the function of the permanent vacuole?
Supports the cell, maintaining its
turgidity.
What is the function of chloroplasts?
Site of photosynthesis
Describe how sperm cells in animals are adapted to
their function
● Haploid nucleus contains genetic information.
● Tail enables movement.
● Mitochondria provide energy for tail movement.
● Acrosome contains enzymes that digest the egg cell
membrane.
Describe how nerve cells in animals are adapted to
their function
● Long axon allows electrical impulses to be transmitted all over
the body from the central nervous system.
● Dendrites from the cell body connect to and receive impulses
from other nerve cells, muscles and glands.
● Myelin sheath insulates the axon and speeds up the
transmission of impulses along the nerve cell.
Describe how root hair cells in plants are adapted to
their function
● Large surface area to absorb nutrients and
water from surrounding soil.
● Thin walls meaning short diffusion distance.
lotf of mitochondria to provide nrg for active transport
Describe how muscle cells are adapted to their
function
● Arrangement of protein filaments allows them to
slide over each other to produce muscle contraction.
● Mitochondria to provide energy for muscle
contraction.
● Merged cells in skeletal muscle allow muscle fibre
contraction in unison.
Describe how xylem cells in plants are adapted to
their function
● No upper or lower margins between cells
to provide a continuous route for water to flow.
● Thick, woody side walls strengthen their
structure and prevent collapse.
What is cell differentiation?
The process by which cells become
specialised.
Describe how phloem cells in plants are adapted to
their function
● Sieve plates let dissolved amino acids and
sugars be transported up and down the stem.
● Companion cells provide energy needed for
active transport of substances along the
phloem.
Why is cell differentiation important?
Allows production of different tissues and
organs that perform various vital
functions in the human body
What changes does a cell go through as it
differentiates?
Becomes specialised through acquisition
of different sub-cellular structures to
enable a specific function to be
performed by the cell.
At what point in their life cycle do most animal cells
differentiate?
Early in their life cycle
For how long do plant cells retain the ability to
differentiate?
throughout their life
What is the purpose of cell division in mature
animals?
growth and repair
Define resolution
The smallest distance between two
objects that can be distinguished.
Define magnification
The number of times bigger an image
appears compared to the size of the real
object.
How does a light microscope work?
Passes a beam of light through a specimen
which travels through the eyepiece lens,
allowing the specimen to be observed.
What are the advantages of light microscopes?
● Inexpensive
● Easy to use
● Portable
● Observe both dead and living specimens
What is the disadvantage of light microscopes?
Limited resolution
Name the two types of electron microscope
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)
How does an electron microscope work?
It uses a beam of electrons which are
focused using magnets. The electrons hit
a fluorescent screen which emits visible
light, producing an image.
Why do electron microscopes have a greater
magnification and resolution?
They use a beam of electrons which has
a shorter wavelength than photons of
light.
What is the advantage of electron microscopes
Greater magnification and resolution.
How have electron microscopes enabled scientists
to develop their understanding of cells?
● Allow small sub-cellular structures (e.g. mitochondria,
ribosomes) to be observed in detail.
● Enable scientists to develop more accurate
explanations about how cell structure relates to
function.
What are the disadvantages of electron
microscopes?
Expensive
● Large so less portable
● Require training to use
● Only dead specimens can be observed
How can the magnification of an image be
calculated?
magnification =
size of image / size of real object
What is standard form?
A way of expressing numbers - written as
a figure between 1 and 10 multiplied by a
positive or negative power of 10.
How do bacteria multiply
Binary fission
How often do bacteria multiply
Once every 20 minutes if enough
nutrients are available and the
temperature is suitable.
State 2 ways in which bacteria can be grown
● Nutrient broth solution
● Colonies on an agar gel plate
What nutrients make up a nutrient broth solution?
All nutrients required for bacteria to grow
including nitrogen for protein synthesis,
carbohydrates for energy and other
minerals.
What are uncontaminated cultures of
microorganisms needed for?
Investigating disinfectant and antibiotic
action
Why must Petri dishes and culture media
be sterilised before use?
To kill any bacteria already present.
Why must inoculating loops be sterilised by passing
them through Bunsen burner flame?
To kill any bacteria present on the
inoculating loop
Why are cultures incubated at 25oC in school
laboratories?
Harmful pathogens are less likely to to
grow at this temperature.
Why must the Petri dish lid be secured with adhesive
tape and the whole dish stored upside down?
Stops bacteria in the air contaminating the culture.
The lid is not fully sealed to prevent the growth of
anaerobic bacteria in a lack of oxygen.
Upside down to prevent condensation from forming
and dripping down onto the colonies.
How is the number of bacteria in a population after a
certain time calculated from the mean division time?
. Calculate the number of times the bacteria will divide in the given time period
from the mean division time.
2. Use the following equation to calculate the number of bacteria:
Number of bacteria in population at end of time period = number of bacteria at
the beginning of the time period x 2number of divisions in the time period
. Express the answer in standard form if possible.
How many chromosomes are found in the
nucleus of human body cells?
46 - 23 pairs
What are chromosomes made up of?
Chromosomes consist of DNA molecules
combined with proteins. They contain
genes which provide the instructions for
protein synthesis.
How many chromosomes are found in the nucleus of
gametes?
23 (not pairs, just 23 chromosomes)
What is a gene?
A section of DNA which codes for a
protein.
What are the three main stages of the cell
cycle?
growth
2. dna synthesis
3. mitosis
How are chromosomes arranged in the
nucleus of a body cell?
Arranged in pairs - 46 chromosomes
form 23 pairs.
Why is mitosis important?
● Produces identical cells which all have the
same genetic information.
● Produces additional cells for growth and
repair.
What is the function of stem cells in embryos?
Embryonic stem cells can replicate themselves and
differentiate into many other types of cells.
Embryonic stem cells may be able to treat conditions
such as paralysis and diabetes by dividing to replace
damaged cells.
Describe the second stage of the cell cycle
Each chromosome in a pair is pulled to
opposite poles of the cell, then the nucleus
divides.
Describe the first stage of the cell cycle
Longest stage - cells grow and increase
in mass, replicate DNA and synthesise
more organelles (eg. mitochondria,
ribosomes).
Describe the third stage of the cell cycle
The cytoplasm and cell membrane divide -
two identical daughter cells are produced.
What is a stem cell?
An unspecialised cell which is capable of
differentiating into other cell types and of
self-renewal.
What is the function of stem cells in adult bone
marrow?
Adult stem cells can differentiate into several cell
types to replace dead or damaged tissues. For
example, bone marrow stem cells can form many
different types of blood cell.
What is the function of stem cells in plant
meristems?
Meristem stem cells retain the ability to
differentiate into any type of plant cell throughout
their lifespan - they can differentiate into any cell
which is required by the plant.
What is therapeutic cloning?
A cloning method where an embryo is produced
with the same genetic makeup as the patient.
The stem cells which originate from the embryo
will not be rejected by the patient’s immune
system, so can be used to treat certain medical
conditions.
What are issues are associated with the use of
stem cells?
● Many embryonic stem cells are sourced from aborted embryos -
some people have an ethical/religious objection.
● Development of stem cell therapies is slow, expensive and difficult.
● Adult stem cells infected with viruses could transfer infections to
patients.
● If donor stem cells do not have a similar genetic makeup to the
patient, an immune response could be triggered.
What are the advantages of cloning plants using
meristem stem cells?
● Can prevent rare plants from becoming extinct.
● Can produce large numbers of plants with a
favourable characteristic.
● Can produce identical plants for research.
What is diffusion?
The net movement of particles from an
area of higher concentration to an area of
lower concentration.
What three main factors affect the rate of
diffusion?
● Concentration gradient - larger gradient, faster
diffusion.
● Temperature - higher temperature, faster diffusion.
● Surface area - larger surface area, faster diffusion.
Give examples of substances transported by diffusion in
the lungs and the kidney
Lungs: oxygen diffuses into the blood from the lungs
and carbon dioxide diffuses into the lungs from the
blood, both down their concentration gradient.
● Kidney: urea diffuses from cells into blood plasma so
it can be excreted in urine.
How are single-celled organisms adapted for
diffusion
They have a large surface area to volume
ratio - maximises the rate of diffusion of
molecules to meet the organism’s needs.
How is surface area to volume ratio calculated?
Surface Area = Number of Sides x (Side
Length x Side Width)
Volume = Length x Width x Depth
Ratio = Surface Area:Volume
What four factors increase the effectiveness of a
gas exchange surface?
● Large surface area
● Thin membrane (short diffusion path)
● Efficient blood supply (animals)
● Ventilation (animals)
What is osmosis?
The movement of water from a dilute solution
to a concentrated solution through a partially
permeable membrane.
What is meant when a solution is isotonic to a cell
The concentrations of the external and
internal (inside cell) solutions are the same.
What is meant when a solution is hypertonic to a
cell?
The concentration of the external solution is
higher than that of the internal solution (inside
cell).
What is meant when a solution is hypotonic to a
cell?
The concentration of the external solution is
lower than that of internal solution (inside
cell).
What may happen when an animal cell is placed
in a very hypotonic solution?
Water moves into the cell, causing it to burst
What may happen when an animal cell is placed
in a very hypertonic solution?
Water moves out of the cell, causing it to shrivel
up.
How do plant leaves and stems remain rigid?
Turgor pressure - water moves in by osmosis,
causing the vacuole to swell and the cytoplasm
to press against the cell wall.
What may happen when a plant cell is placed in a
very hypertonic solution?
Water moves out of the cell by osmosis and the
vacuole and cytoplasm decrease in size. The cell
membrane may pull away from the cell wall,
causing the cell to become plasmolysed.
What is active transport?
The movement of molecules from a more
dilute solution to a more concentrated solution
against a concentration gradient, using energy
from respiration.
How do plant root hair cells use active transport?
Root hair cells use active transport to take
up mineral ions from a more dilute solution in
soils. Ions such as magnesium and nitrates
are required for healthy growth.
How is active transport used to absorb the
products of digestion?
Active transport is used to transport glucose from a
lower concentration in the gut to a higher
concentration in the blood. Glucose is then
transported to the tissues where it can be used in
respiration
photo tactic
plant moving to or away from sunlight and water
effect of alcohol on smal intestines
less digestive enzymes released in SI
too much drinking also result in damaed villi and villi becoming shorter
coeliac disease symptoms
weight loss, tiredness and stomach pain
coeliac disease
villi structure changes
copd
collection of lung diseases e.g chronic bronchitis, emphysema, chronic obstructive airways
symptoms copd
increasing breathlessness when active
persistent cough with phlegm
frequent chest infection
why copd happening
main cause: smoking
smoking irritates and inflames the lungs, resulting in scarring
gene is???
section of dna coding for particular characteristic
gamete???
organisms reproductive cells
e.g egg and sperm, and egg and pollen for plants
haploid vs diploid
Haploid cells contain only one set of Chromosomes. Diploid, as the name indicates, contains two sets of chromosomes
down syndrome
reduced muscle tone leading to floppiness (hypotonia)
eyes slanting upwards and downwards
small mouth with protruding tongue
flat back of head
below average weight and length at birth
turners syndrome
affects onnly females
low growth n development
why do we need cells to multiply
for reproduction
for growth and repair
stage 1 cell cycle
growth: num of subcellular structures increases
stage 2 cell cycle
dna synthesis: dna replicates to form two copies of each chromosome
stage 3 cell cycle
mitosis: prophase
metaphase
anaphase
telaphase
prophase
chromosomes become visible as they condense
metaphase
nucleus disassembles, chromosomes line up in middle of cell, prepare to seperate
anaphase
sister chromatids seperated. move to either poles. structure called spindle fibre helps chromatids move
telaphase
2 new nuclei begin to form around chromosomes at each pole of cell.
cell divides, 2 identical daughter cells formed
zygote??
fertilised egg cell
how embryo happen
zygote divides by mitosis into embryo. made from undifferentiated cells called stem cells
cell differentiation
process by which cells become specialised
how does most plant growth occur
by cell elongation
what triggers stem cells to differentiate
certain genes turning on and off
meristem divison
have ability to divdie over and over again
embryonic stem cells vs adult stem cells
embryonic: differentiate into most types of human cell
adult: differentiate into many types of cell
embryos produedby therapeutic cloning
same genetic makeup as patient
other pronblems with therapeutic cloning
baby hasnt consented
more eggs fertilised than needed
