What are the main characteristics of a eukaryotic organisms?
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What are the main characteristics of a eukaryotic organisms?
A eukaryotic organism is an organism whose cells contain membrane-bound organelles including a nucleus, cytoplasm and a cell membrane.
True or False?
Prokaryotic organisms contain a nucleus.
False.
Prokaryotic organisms do not contain a nucleus.
Define prokaryotic organism.
A prokaryotic organism is an organism whose cells lack a nucleus and other membrane-bound organelles.
They have cytoplasm and a cell membrane surrounded by a cell wall.
True or False?
All prokaryotic organisms are single-celled.
True.
Prokaryotic organisms are always single-celled.
Define the term plasmid.
A plasmid is a small circular loop of DNA found in prokaryotic cells.
True or False?
Eukaryotic cells are larger than prokaryotic cells.
True
Eukaryotic cells are larger than prokaryotic cells.
Eukaryotic cells are typically between 10 and 100 µm. Prokaryotic cells are much smaller in comparison to eukaryotic cells, with many measuring ~ 1 µm in size.
How many micrometres (µm) are in a millimetre (mm)?
There are 1000 µm in 1 mm
There are 1,000,000 nanometres in a millimetre.
What is 1,000,000 in standard form?
1,000,000 in standard form is 1 x 106
True or False?
To convert a measurement from nanometres to micrometres you must multiply by 1000.
False
To convert a measurement from nanometres to micrometres you must divide by 1000
If a eukaryotic cell is 100µm wide and prokaryotic cell is 1µm wide, how much bigger is the eukaryotic cell in terms of orders of magnitude?
The eukaryotic cell is 2 orders of magnitude wider than the prokaryotic cell
1 = 100 and 100 = 102, therefore it is 2 orders of magnitude wider
Be careful to check the units when comparing two numbers
What separates cells from their surrounding environment?
The cell membrane separates cells from their surrounding environment.
Name the largest organelle present within animal cells.
The largest organelle within animal cells is the nucleus.
Name the structures present in plant cells that are not present in animal cells.
Plant cells have the following structures that are not present in animal cells:
Cell wall
Chloroplasts
Permanent vacuole
True or False?
Ribosomes are present in both plant and animal cells.
True.
Ribosomes are present in plant and animal cells. They are the site of protein synthesis.
Name three organelles found within animal cells.
Organelles present within animal cells are:
Nucleus
Mitochondria
Ribosomes
Note that structures such as the cell membrane and cytoplasm are not organelles, so are not acceptable answers here.
What is the smallest organelle present in both plant and animal cells?
Ribosomes are the smallest organelle; they are present in both plant and animal cells.
True or False?
The gel-like fluid present inside both plant and animal cells is the chloroplast.
False.
The gel-like fluid present in plant and animal cells is the cytoplasm. Chloroplasts are organelles found in plant cells.
True or False?
The role of the nucleus is to release energy for the cell.
False.
The role of the nucleus is to store genetic information in the form of DNA. Energy is released by the mitochondria.
What is the function of chloroplasts within plant cells?
Chloroplasts absorb light energy during the process of photosynthesis.
True or False?
Plant cell walls are responsible for controlling the passage of substances in and out of cells.
False.
Plant cell walls provide strength and additional structural support for plant cells. It is the membrane that regulates the passage of substances.
What is the function of the permanent vacuole in plant cells?
The permanent vacuole stores cell sap and provides structural support for plant cells.
True or False?
Mitochondria are the site of aerobic respiration.
True.
Mitochondria are responsible for releasing energy through the process of aerobic respiration.
Define the term specialised cell.
Specialised cells are cells that have developed specific characteristics that allow them to perform particular functions.
Give an example of a specialised plant cell.
Examples of specialised plant cells include:
root hair cell
palisade mesophyll cell
xylem and phloem cells
Give an example of a specialised animal cell.
Examples of specialised animal cells include:
red blood cells
nerve cells
ciliated epithelial cells
sperm / egg cells
muscle cells
You specifically need to know sperm cells, nerve cell and muscle cells
True or False?
Root hair cells have an increased surface area.
True.
Root hair cells have an increased surface area to allow increased absorption of water and mineral ions from the soil.
What is the function of a nerve cell?
The function of a nerve cell is to conduct electrical impulses and send signals around the body.
True or False?
An adaptation of a muscle cell is that they contain a lot of mitochondria.
True.
Muscle cells contain a lot of mitochondria to carry out aerobic respiration and provide energy for muscle contraction.
True or False?
Sperm cells contain a full set of chromosomes (46) from the father.
False.
Sperm cells contain half the amount of DNA contained to normal body cells.
Why are root hair cells adapted to contain a large number of mitochondria?
Root hair cells contain a lot of mitochondria to provide energy for the active transport of mineral ions from the soil into the cell.
What is the function of a phloem cell?
Phloem cells form a long vessel to allow the plant to transport dissolved sugars and amino acids.
True or False?
Phloem vessels are strengthened and supported by a substance called lignin strengthening the tubes and providing support for the plant.
False.
Xylem vessels are supported by lignin.
What is cell differentiation?
Cell differentiation is the process by which a cell changes to become specialised.
True or False?
Almost all cells in a multicellular organism contain different genetic information.
False.
Almost all cells in a multicellular organism contain the same genetic information.
What determines the features of specialised cells?
The features of specialised cells are determined by the expression of genes in the nucleus.
True or False?
All plant cells differentiate early in development.
False.
Many types of plant cells retain the ability to differentiate throughout life.
When does most cell differentiation occur in animals?
In animals most cell differentiation take place during the early stages of development when the animal is an embryo/fetus (before it is born).
What is a light microscope?
A light microscope is an instrument that uses light and lenses to magnify specimens, allowing visualisation of cells and large subcellular structures.
What does resolution mean in microscopy?
Resolution in microscopy means the ability to distinguish between two closely spaced objects as separate entities.
What is an electron microscope?
An electron microscope is an instrument that uses electron beams instead of light to provide much higher resolution and magnification than light microscopes.
True or False?
Electron microscopes use light beams for imaging.
False.
Electron microscopes use electron beams for imaging.
True or False?
Upon the invention of the light microscope in the 17th century, scientists were able to view cell structure in detail.
False.
The first light microscopes to be invented allowed only very basic details of cell structure to be observed, such as cell shape and the plant cell walls.
What is the formula for calculating magnification?
The formula for calculating magnification is:
magnification = image size ÷ actual size
True or False?
Magnification has units.
False.
Magnification does not have any units and is just written as, e.g. x10 or 5000x.
What is the equation for calculating the actual size of a specimen?
The equation for calculating the actual size of a specimen is:
actual size = image size ÷ magnification
What is the purpose of a magnification scale in microscope drawings?
A magnification scale is included to show the actual size of the observed specimen.
What is a microscope slide?
A microscope slide is a thin, flat piece of glass on which specimens are prepared for observation under a microscope.
What stain is used for cheek cells?
Methylene blue is used to stain cheek cells.
True or False?
Iodine is used to stain onion cells.
True.
Iodine is used to stain onion cells.
What should be avoided when preparing a microscope slide?
Smudging the glass slide and trapping air bubbles under the coverslip should be avoided when preparing a microscope slide.
What is an objective lens?
An objective lens is the lens on a microscope that is closest to the specimen. Most light microscopes have several objective lenses at different powers for viewing specimens at different levels of magnification.
True or False?
The highest-powered objective lens should always be used first when viewing a specimen under a light microscope.
False.
When viewing a specimen under a light microscope the low-power lens should always be used first.
What are the key characteristics of biological drawings?
Biological drawings should follow specific rules, e.g.:
use a sharp pencil
pencil lines should be clear and unbroken
all structures drawn should be in proportion
identifiable features must be labelled using straight, uncrossed lines
How large should biological drawings be?
Biological drawings should take up at least half of the space available on the page
Define the term binary fission.
Binary fission is a type of simple cell division by which bacteria multiply.
What happens to the number of bacterial cells after a binary fission event?
The number of bacterial cells increases by a power of 2 (doubles) each time binary fission occurs.
What is aseptic technique?
Aseptic technique is a method used to prevent contamination by unwanted microorganisms when working with cultures.
True or False?
Lifting the lid of a petri dish only slightly when transferring bacterial cultures is primarily to prevent air from entering.
False.
Lifting the lid of a petri dish only slightly primarily reduces the risk of contamination by other microorganisms.
Why should the inoculating loop be passed through a hot flame before it is used to transfer bacteria to a culture medium?
The inoculating loop should be passed through a hot flame to kill any microorganisms present on the loop; this prevents contamination.
Why should the lid of the petri dish be secured with tape at intervals around the dish, rather than all the way around?
The lid should be secured with tape at intervals, rather than all the way around, to ensure that oxygen can enter the dish; this prevents the growth of anaerobic bacteria which may be harmful.
What is the highest incubation temperature for growing bacteria in a school lab and why?
The maximum allowed temperature for growing bacteria in a school lab is 25°C.
This is to restrict the growth of harmful pathogens.
What is an inhibition zone in the context of culturing microorganisms?
An inhibition zone is an area around a disc of antibiotic, antiseptic, or disinfectant where bacterial growth is inhibited.
What is the equation for calculating the area of an inhibition zone?
The equation for calculating the area of an inhibition zone is:
Area of inhibition zone = πr2
Where π = 3.14
and r = the radius of the zone of inhibition
What is the mean division time of bacteria?
Mean division time is the average length of time that it takes for a bacterial cell in a population to divide.
True or False?
A large zone of inhibition indicates that the antibiotic is effective at killing the bacteria.
True.
The bigger the zone of inhibition, the more effective the antibiotic is at killing the bacteria.
What is indicated by the absence of a zone of inhibition around an antibiotic disc?
If there is no zone of inhibition it indicates that the bacteria is resistant to a particular antibiotic.
When investigating the effect of antibiotics on bacterial growth using agar plates and zones of inhibition, what should be used as an experimental control?
When investigating the effect of antibiotics on bacterial growth using agar plates and zones of inhibition the control should be paper discs soaked in sterile water.
How can microorganisms be cultured for use in an investigation?
Bacteria can be cultured in a nutrient broth solution or as colonies on an agar gel plate.