cell structure Flashcards
Where is the genetic material in a prokaryotic cell?
In a bacterial DNA loop and there may be one or more plasmid rings.
Where is the genetic material in a eukaryotic cell?
The DNA is in chromosomes enclosed in a nucleus.
Why do scientists use prefixes?
To make very small numbers more manageable
sperm functions and features
function is to fertilise an egg.
- streamline with long tail to swim faster
- acrosome in head to digest egg cell membrane
- large number of mitochondria to release energy for swimming
nerve functions and features
function is to carry electric signals
-long to carry signals long distances
-branched connections to connect with other nerve cells and form a network around the body
insulating sheath to enhance transmissions of electric signals
muscle functions and features
function is to contract to allow movement
- contain a large number of mitochondria to release energy from respiration for movement
- long so that there is enough space to contract
root hair functions and features
function is to absorb water and minerals from the soil
-hair like projections to increase the surface area
xylem functions and features
function is to carry water and minerals in plants
- form hollow xylem tubes made of dead tissue
- cells have end plates with holes in them
- glucose in solution moves from leaves to growth and storage tissues in a process called TRANSLOCATION
cytoplasm
where chemical reactions happen
motchondria
most energy is released by respiration here
ribosomes
protein synthesis happens here
vacuole
filled with sap to make cell stronger
plasmid
small ring of dna used in genetic modification
What does cell differentiation mean?
When a cell changes to become specialised.
In what stage of an animal’s life cycle do most cells differentiate?
early stages
In mature animals when do cells still need to differentiate?
for replacement and repair of cells
In what stage of their life cycle do plant cells differentiate?
they differentiate throughout
Define the term resolution.
The shortest distance between two objects that can be seen clearly.
What are the advantages of the electron microscope?
Electron microscopes
have a higher magnification and resolution than light microscopes
Name the smallest cell structures that can be seen by the light microscope?
Nuclei and mitochondria
What are the smallest cell structures that can be seen by the electron
microscope?
internal structures of mitochondria and chloroplasts.
magnification equation
magnification = size of image/size of real object
Describe how you would make an onion cell slide.
-Place thin section of onion epidermis onto slide.
-Place a drop of iodine in the middle of the slide to stain the onion.
-Gently lower cover slip onto the onion without trapping air
bubbles.
-Soak up any excess liquid with a paper towel.
Describe how you would use the light microscope to view onion
cells.
-Switch on the light source and place your slide on the stage.
-Use the lowest objective lens and turn the focusing wheel to move
the lens close to the slide.
-Slowly adjust the focusing wheel until you can see a clear image.
-Increase the magnification by changing the objective lens and re-focus.
What is ‘binary fission’?
Cell division where two identical cells to the
parent cell are formed.
Why do you need to sterilise Petri dishes and culture mediums before
use?
To kill any unwanted microorganisms.
What would you use an inoculating loop for?
To transfer bacteria onto
the agar.
How do you sterilise an inoculating loop?
By heating in a Bunsen flame.
How would you secure the lid of the Petri dish?
With tape but not sealed
all the way around.
What temperature would you incubate the samples at in a school and why should you use this temperature?
25oC, to prevent the growth of pathogens harmful to humans.
How can you test the effectiveness of antibiotics and disinfectants on
bacteria?
Inoculate agar with bacteria, place discs soaked in the solutions
(water as a control) and place the discs on the agar containing bacteria.
Incubate at 25oC.
What is the zone of inhibition?
An area where bacteria don’t grow.
What are chromosomes?
Coiled strands of DNA molecules.
what is a gene?
a section of dna that codes for a protien
What is DNA?
A genetic material found in the nucleus that codes for proteins.
Where in a cell do you find chromosomes?
In the nucleus of cells.
How many chromosome pairs do you find in a human body cell?
23
What are the three stages of the cell cycle?
Growth, DNA synthesis and mitosis.
What is mitosis and what is it used for in animals and plants?
Growth, repair and asexual reproduction.
what is a stem cell
a cell that is undifferentiated
Which type of human stem cell can differentiate into any human
cell?
embryo stem cells
What is therapeutic cloning?
Where patients are given stem cells
containing the same genes as theirs.
What are the risks of therapeutic cloning?
Viral infections.
State two reasons why people may object to the use of stem cells
in therapeutic cloning.
Ethical and religious reasons.
What are meristems?
Structures in plants that contain stem cells.
State two reasons that plants are cloned?
To clone rare species of
plants and to clone crop plants with useful characteristics.
Define ‘diffusion’?
The spreading of the particles from a region where they are of a
higher concentration to an area of lower concentration.
State three places where diffusion occurs in the body.
Small intestines, lungs, kidneys
What is a concentration gradient?
The difference in concentration
between two areas next to each other.
What three factors affect rate of diffusion?
Concentration gradient,
temperature, surface area.
What is surface area to volume ratio?
The size of a surface
compared to its volume.
Which has the largest surface area to volume ratio an elephant or a
meerkat?
The meerkat.
how the small intestines are adapted for diffusion
Have villi to increase surface area, good
blood supply, thin membranes.
how the lungs are adapted for diffusion
Have alveoli to increase surface area, good blood supply, thin membranes, they are ventilated.
how gills in fish are adapted for diffusion
Have gill filaments and lamella to increase surface
area, good blood supply, thin membranes.
how roots are adapted for diffusion
Have root hair cells to increase surface area.
how leaves are adapted for diffusion
Large surface area, thin and stomata.
Define osmosis?
Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
What is a partially permeable membrane?
A membrane that lets
some but not all substances through.
What happens to an animal cell in a hypertonic solution?
It will lose water by osmosis and shrivel.
What happens to an animal cell in a hypotonic solution?
It will absorb water by osmosis and get bigger/burst.
Define active transport.
Active transport moves substances from a
more dilute solution to a more concentrated solution (against a
concentration gradient) using energy from respiration.
Why does active transport need to occur in root hair cells?
Because the minerals are at a higher concentration in the roots than in the soil.
Why does active transport need to occur in the gut?
Because the glucose in the blood is at a higher concentration than in the gut.
