Topic 1- Cell structure 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 is the prokaryotic cell wall composed of?
Peptidoglycan
How is genetic Information stored in a prokaryotic cell?
Chromosomal DNA (single large loop of circular DNA)
Plasmid DNA
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 eg antibiotic resistance
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 meters
What is a millimetre (mm)?
1x10^-3 metres
What is micrometer?
1 x 10^-6 meters
What is a nanometer?
1 x 10^-9 meters
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 eg first stage of respiration
Transport medium
What is the function of the cell membrane?
Controls the entry and exit of material into and out of the cell
What is the function of the mitochondria?
Site of later stages of aerobic respiration in which ATP is produced
What is the 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
What is the 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
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 provides 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, muscle and glands
Myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell
Describe how muscles in animals are adapted to their function
Arrangement of protein filaments allow 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 the root hair cells in plants are adapted to their function
large surface area to absorb nutrients and water from surrounding soil
Thin walls that do not restrict water absorption
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
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
What is cell differentiation?
The process by which cells become specialised
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital functions in the human body
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 entire life cycle
What is the 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
Define magnification
The number of times bigger an image appears compared to the size of the real object
Define resolution
The smallest distance between two objects that can be distinguished
How does a light a microscope work?
passes a beam of light through the specimen which travels through the eyepiece lens, allowing the specimen to be observed
What are the advantages of light microscopes? (4)
Inexpensive
Easy to use
Portable
Observe both dead and living specimens
What is the disadvantage of light microscopes?
Limited resolution
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
Name the two type of electron microscope
Transmission electron microscope (TEM)
scanning electron microscope (SEM)
What is the advantage of electron microscopes?
Greater magnification and resolution
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
How have electron microscopes enabled scientists to develop their understanding of cells?
Allow small sub-cellular structures 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? (4)
Expensive
large so less portable
require training to use
only dead specimens can be observed
How can magnification be calculated?
Magnification= size of image/ size of real object
How do bacteria multiply
Binary fission
How often do bacteria multiply?
Once every 20 minutes if enough nutrients are available ant 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
Describe the preparation of an uncontaminated culture using aseptic technique
1) use pre-sterilised plastic petri dishes or sterilise glass Petri dishes and agar gel before using with an autoclave
2) Pour the sterile agar gel into the Petri dish and allow time to set
3) sterilise the inoculating loop by passing it through a Bunsen burner flame
4)dip the inoculating into the solution of microorganisms and make streaks with the loop on the surface of the agar
5) put the lid on the Petri dish and secure it with tape. Label accordingly then turn and store upside down.
6) Incubate the culture at 25degree Celsius in school laboratories
Why must Petri dishes and culture media be sterilised before use?
to kill any bacteria already present
Why must the inoculating loops be sterilised by passing them through the Bunsen burner flame?
to kill any bacteria present on the inoculating loop
Why must the Petri dishes lid be secured with 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
Why are cultures incubated at 25 in school labs?
harmful pathogens are less likely to grow at this temperature
What is the formula used to calculate the cross-sectional area in the inhibition zone?
π r²
How is the number of bacteria in population after a certain time calculated from the mean division time?
1)calculate the number of times the bacteria will divide in the given time period from the mean division time
2) number of bacteria population at the end of time period = number at the beginning of the time period x 2 ^number of division in the time period
