T1 cell structure Flashcards
two types of cells
eukaryotic (plant and animal)
prokaryotic (bacteria)
differences between eukaryotic and prokaryotic cells?
P - smaller
E - contain membrane bound-organelles and nucleus containing genetic material
what is the prokaryotic cell wall composed of?
peptidoglycan
how is genetic information stored in a prokaryotic cell?
found free within cytoplasm as:
chromosomal DNA (single large loop of circular DNA)
plasmid DNA
what are plasmids?
small, circular loops of DNA found free in cytoplasm and separate from the main DNA
carry genes that provide genetic advantages
order of magnitude?
power to the base 10 used to quantify and compare size.
list the components of both plant and animal cells
nucleus cytoplasm cell membrane mitochondria ribosomes
list 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.
function of the cytoplasm
site of cellular reactions
transport medium
function of the cell membrane
controls the entry and exit of materials into and out of the cell
function of the mitochondria
site of later stages of aerobic respiration in which ATP is produced
function of the ribosomes
joins amino acids in a specific order during translation for the synthesis of proteins.
what is the plant cell wall made of
cellulose
function of the plant cell wall
provides strength
prevents the cell bursting when water enters by osmosis
what does the permanent vacuole contain?
cell sap (solution of salts, sugars and organic acids)
function of the permanent vacuole
supports the cell, maintaining its turgidity.
function of the chloroplasts
site of photosynthesis
describe how sperm cells in animals are adapted to their function
haploid nucleus - contains genetic information
tail - enables movement
mitochondria - provides energy for tail movement
acrosome - contains enzymes that digest the egg cell membrane
describe how nerve cells in are adapted to their function
long axon - allows electrical impulses to be transmitted all over the body from CNS
dendrites - from the cell body connect to and receive impulses from other nerve cells, muscles and glands
myelin sheath - insulates axon and speeds up the transmission of impulses along the nerve cell
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 - provides energy for muscle contraction
merged cells in skeletal muscle - allow muscle fibre contraction in unison.
describe how root hair cells in plants are adapted to their function
large surface area - absorbs nutrients and water from surrounding soil
thin walls - don’t restrict water absorption.
describe how xylem are adapted to their function
no upper or lower margins between cells - provide a continuous route for water to flow
thick, woody side walls - strengthen their structure and prevent collapse
describe how phloem cells 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
what is cell differentation
process by which cells become specialised
why is cell differentiation important
allows production of different tissues and organs that perform various vital function in the human body
At what point in their life cycle do most animal cells
differentiate?
early in their life cycle
how long do plant cells retain the ability to differentiate?
throughout their entire life cycle
purpose of cell division in mature animals
repair and replacement of cells
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.
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
advantages of light microscopes (4)
inexpensive
easy to use
portable
observe both dead and living specimens
disadvantage of light microscopes
limited resolution
how does an electron microscope work
uses a beam of electrons which are focused using magnets.
electrons hit a fluorescent screen which emits visible light, producing an image
name the two types of electron microscope
transmission electron microscope (TEM)
scanning electron microscope (SEM)
advantages of electron microscopes
greater magnification and resolution
why do electron microscopes have a greater magnification and resolution?
use a beam of electrons which has a shorter wavelength than photons of light.
how have electron microscopes enable scientists to develop their understanding of cells?
allow small sub-cellular structures to be observed in detail
enable them to develop more accurate explanations about how cell structure relates to function
disadvantages of electron microscopes (4)
expensive
large so less portable
require training to use
only dead specimens can be observed
magnification equation
mag=
size of image/
size of real image
how do bacteria multiply
binary fission (simple cell division)
how often do bacteria multiply
once every 20 mins if enough nutrients are available and the temperature is suitable
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
describe the preparation of an uncontaminated culture using aseptic technique
- use pre-sterilised plastic petri dishes or sterilise glass petri dishes and agar gel before using with an autoclave
- pour the sterile agar gel into the petri dish and allow time to set
- sterilise the inoculating loop by passing it through a Bunsen burner flame
- dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar
- put the lid on the dish and secure with tape, label and store upside down
- incubate at 25C in school labs
why must petri dishes and culture media be sterilised before use
kill any bacteria already present
why must inoculating loops be sterilised by passing them through Bunsen burner flame
kill any bacteria present already
why must a Petri dish be secured with tape and stored upside down
stops bacteria in the air contaminating the culture
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
why are cultures incubated at 25C in school laboratories
harmful pathogens are less likely to grow at this temperature
what is the formula used to calculate cross-sectional area of a bacteria colony or clear area around a bacterial colony
πr2
= 3.14
r = radius (diameter/2)
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. - 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.
