B1 cell biology Flashcards
properties of prokaryotic cells
no nucleus
genetic material stored in single loop of dna
no chloroplasts or mitochondria
some prokaryotic cells contain plasmids
plasmids can replicate and move between cells so genetic info can be shared
cell membrane
controls what goes in and out of the cell - selectively permeable
ribosomes
responsible for synthesising (making) proteins
mitochondria
organelles where aerobic respiration happens
releases energy out body needs to function
permeable vacuole
fluid filled sac that stores water
enclosed in a membrane
can make up to 90% of plant volume
differentiation in plants
can differentiate throughout life
which means plants are always able to create new tissues
differentiation in animals
earlier on in development
in mature animals cells mostly divide to replace and repair ones that are already there
new tissues are rarely created by cell differentiation
when does differentiation occur
when cells acquire different sub cellular structures
flagella
some bacteria have flagella l
whip like structures used for movement
sun cellular structures inside bacteria
flagella
cytoplasm
plasmids
cell wall and cell membrane
what is cell differentiation
where a cell develops new sub cellular structure to let it perform a specific function
this makes the cell specialised
embryos
cell differentiation in animals starts during an organisms development
organisms start one
these cells divide to form embryos that differentiate to produce that perform all the body’s functions
sperm cell
specialised
flagellum
middle section-provides sperm with energy
head-carries nucleus
acrosome-found at tip of head, contains digestive enzymes to penetrate the egg cell
nerve cells
specialised to send electrical signals around the body
axon
myelin sheath
dentrites
axon
part of the cell that electrical signals travel along
nerve cells have a long axon - this increases the distance electrical impulses can travel
myelin sheath
sheath made of material called myelin
surrounds axon on nerve cell
this increases speed of transmission of electrical signals and stop’s electrical nerve signals leaking out
dendrites
branches of nerve cells
several dendrites spread outwards form the cell body to transfer electrical messages to other neurons
electrical messages travel between neurons and synapses
xylem cells
specialised to transport water up the stem of a plant and into the leaves
open ended cells- xylem vessels are made up of a series of connected dead xylem cells
the end walls of the dead cells are broken to allow water to move through
lignin- strengthens cell walls of xylem cells
phloem
The phloem is specialised to transport food products to parts of the plant where they are needed. Phloem vessels are made up of columns of living cells.
The end walls of phloem cells contain small holes to allow food products to move up and down the phloem vessels throughout the plant
resolution
Resolution is the ability to distinguish between (tell apart) two or more objects that are close together.
magnification
Magnification tells us how many times larger an image seen through a microscope is compared to the real object.
Magnification = image size ÷ actual size
light microscope
A light microscope passes light through a specimen and creates a magnified image using lenses.
Light microscopes allowed bacteria to be seen for the first time. They also allowed us to see plant cells and animal cells as separate objects
electron microscope
Electron microscopes work in a similar way to light microscopes. However, electrons are passed through the specimen instead of light
allowed scientists to see sub-cellular structures more clearly.
They also allowed scientists to study how structures such as mitochondria, chloroplasts and ribosomes function.
Light Microscope Experiment
Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide.
Add a few drops of a suitable stain/dye (e.g. iodine).
Place a coverslip on top of the tissue and place the slide onto the microscope stage.
Use the objective lens with the lowest magnification, and focus on the sample.
Increase the magnification and refocus to see different features of the cell.
growing microorganisms
cultures of microorganisms can be used to see the effects of antibiotics and disinfectants which both kill bacteria
microorganisms can be grown in:
-solution of nutrient broth, this contains carbohydrates as an energy source minerals and sometimes other chemicals
-agar gel plate
contamination
if bacteria that are not being investigated grow during culturing microorganisms, then the investigation has been contaminated
risks:
ruins test results
serious health + safety issues
sources:
skin
air
soil
water
prevention:
cultures must be pure
aseptic techniques
flames
boiling
controlled temp (25 degrees)
lids- taped shut and put upside down so air doesn’t get in + to prevent condensation forming on lid and dripping onto agar
the cell cycle
series of events involved in cell growth and division
it involves motor which allows for the growth, repair and asexual reproduction of cells
cell cycle initial stage
extra ribosomes, mitochondria and other sub cellular structures are produced
the cells chromosomes are replicated so that there are two sets of the cells chromosomes
cell cycle- mitosis
the two sets of chromosomes are pulled to opposite ends of the cell
the nucleus divides into two
mitosis ensures that both daughter cells have the same chromosomes as eachother and the parent cell
this is important for processes that require identical cells to be produced
cell cycle- cell division
the cytoplasm and cell membranes are divided resulting in the production of two identical cells
enzymes
a protein which increases the rate of a reaction
known as biological catalysts
active site:
to catalyse a reaction the reacting chemical must bind to the enzymes active site
the active site will only fit specific substrates
factors affecting diffusion
-temperature
-membrane surface area
-concentration gradient:
1)the concentration gradient is linked to the difference in concentration between two areas
2)the bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion.
exchange surfaces
ventilation
large surface area
thin membrane
blood supply
active transport in humans and plants
important for:
sugar absorption in gut- allows sugar molecules to be absorbed from the gut and into the into the blood, even when when the sugar conc in blood is higher
mineral absorption in plants- means that plants are able to absorb mineral ions that at are necessary for healthy growth, even though the conc of minerals is usually lower in the soil than in the root hair
