Cell Biology 1 Flashcards
Eukaryotic and prokaryotic cells, Microscopy.
What are animal, algal, and plant cells types of?
Eukaryotic cells
What are bacterial cells types of?
Prokaryotic cells
What are the differences between eukaryotic and prokaryotic cells?
-Prokaryotic cells are smaller
-Prokaryotic cells don’t have mitochondria or other membrane-bound organelles
-Prokaryotic cells do not have a nucleus but a single strand of DNA
-Prokaryotic cells have plasmids
What are the similarities between eukaryotic and prokaryotic cells?
-Both have cytoplasm, a cell membrane, and ribosomes.
What is an order of magnitude?
Differences in size calculated in factors/powers of ten, for comparing very large and small things.
List the sub-cellular structures in an animal cell
-Nucleus
-Cytoplasm
-Cell membrane
-Mitochondria
-Ribosomes
List the sub-cellular structures in a plant cell:
-Nucleus
-Cytoplasm
-Cell membrane
-Mitochondria
-Ribosomes
-Cellulose cell wall
-Permanent vacuole
-Chloroplasts
What additional sub-cellular structures do plant cells have?
-Cellulose cell wall
-Permanent vacuole
-Chloroplasts
What is the function of the nucleus?
It contains genetic material and controls the activities of the cell.
What is the function of the cytoplasm?
It is a gel-like substance where most of the chemical reactions happen. It contains enzymes that control these reactions.
What is the function of the cell membrane?
Controls which substances can pass in and out of the cell and holds the cell together.
What is the function of mitochondria?
Mitochondria are the site of aerobic respiration. They release energy for the cell.
What is the function of chloroplasts?
Chloroplasts are the site of photosynthesis (which makes food for the plant). They contain chlorophyll.
What is the function of ribosomes?
Ribosomes are the site of protein synthesis.
(they synthesise proteins)
What is the function of the permanent vacuole?
It is a large sac containing cell sap - a weak solution of sugars and salts.
It helps to maintain the structure and shape of the cell by pushing against the cell wall.
What is chlorophyll?
A green pigment found in chloroplasts, which absorbs the light needed for photosynthesis.
What is the function of the cell wall?
It is made up of cellulose so is strong, helping to maintain the shape of the cell.
List the sub-cellular structures in a bacterial cell:
-cell membrane
-cell wall
-cytoplasm
-ribosomes
-nucleoid (singular loop of DNA)
-(plasmids)
-(flagellum - singular, flagella - plural)
What are bacterial cells?
Prokaryotic, unicellular organisms which are approximately 1µm in size (about 10x smaller than human body cells).
What is the function of a nucleoid?
It is a single strand of DNA that contains essential DNA (all DNA that the cell needs to survive and reproduce)
What is the function of plasmids?
They are small rings of DNA which contain extra genes which the bacterial cell does not need on a daily basis, such as for antibiotic resistance.
What is the function of the flagellum?
Rotates or moves in a whip-like motion to move the bacterium.
1 as a power of 10
10⁰
0.1 as a power of 10
10⁻¹
0.01 as a power of 10
10⁻²
0.001 as a power of 10
10⁻³
Increasing a number by one order of magnitude is the same as…
multiplying the number by 10
Decreasing a number by one order of magnitude is the same as…
dividing the number by 10 (equivalent to multiplying by 0.1)
When might we need to use estimations when measuring sub-cellular structures?
To measure the size/ area of subcellular structures that are too small to measure directly.
What are microscopes used for?
To view objects and areas of objects that cannot be seen with the naked eye.
How do we get from nanometers to micrometers?
divide by 1000
how do we get from milimeters to centimeters?
divide by 10
how do we get from a bigger unit to a smaller one?
multiply
how do we get from a smaller unit to a bigger one?
divide
How have microscopy techniques developed over time? How has this led to an increased understanding of sub-cellular structures?
An electron microscope has much higher magnification and resolving power than a light microscope.
This means that it can be used to study cells in much finer detail.
This has enabled biologists to see and
understand many more sub-cellular structures.
How do light microscopes work?
They use light and lenses to form an image of a specimen and magnify it.
The lenses spread out light rays so the image we see is far larger than the object.
They let us see individual cells and larger sub-cellular structures like nuclei.
What is the pathway of light through a light microscope?
light source(mirror)→stage→microscope slide→object→objective lens→body tube→eyepiece lens→eye
Light microscope advantages
-easy to use
-relatively cheap
Light microscope disadvantages
-relies on light which has a wavelength of 0.2 μm
-So, resolution is limited to 0.2 μm
-Meaning any details less than 0.2 μm apart will appear blurry
-So not good enough to study sub-cellular structures
How do electron microscopes work?
They use electrons instead of light to form an image, so have a much higher magnification and resolution than light microscopes, allowing scientists to see things in more detail, like the internal structure of mitochondria and chloroplasts. They even let us see finer things like ribosomes and plasmids.
Resolution
The shortest distance between two points on an object that can still be distinguished as two separate entities.
Lower resolution means…
A blurrier image, as we can’t see in the same level of detail.
Electron microscope advantages
-Use electrons instead of light, which have a wavelength of 0.1nm (so max. resolution is 0.1 nm)
-2000x better resolution than light microscopes
-so gives images with much higher magnifications before becoming blurry and can therefore be used to study sub cellular structures like mitochondria
Electron microscope disadvantages
-Very expensive
-Hard to use (so only used by scientists in laboratories).
How do we calculate magnification?
Magnification = image size ÷ actual size
Magnification
How many times larger the image is than the object.
Image
The image we see when we look down the microscope
Object
The real sample/specimen you’re looking at.
Where is the genetic material of a prokaryotic cell found?
In a single DNA loop and perhaps one or more small rings of DNA called plasmids.
What is the structure of a bacterial (prokaryotic) cell?
Cytoplasm and a cell membrane surrounded by a cell wall. Genetic material not enclosed in a nucleus.
How can we estimate the size of subcellular structures?
-Use the known size of the cell
-Work out how many times the subcellular structure fits into the cell
-Use that number to estimate the size/ area of the sub-cellular structure
What do plant and algal cells have in common?
A cell wall made of cellulose, which strengthens the cell.
What does methylene blue solution bind to in cheek cell microscopy?
nucleic acids like DNA
What do bacterial cells not contain?
Membrane bound organelles such as mitochondria or chloroplasts.
Compare the structure of xylem and phloem tissue.
Xylem tissue is made of dead cells whereas phloem tissue is made of living cells
Xylem tissue contains lignin but phloem tissue does not.
Phloem tissue contains cytoplasm but xylem tissue does not.
There are pores in the end walls of phloem tissue but the xylem tissue has no end walls at all (the cells form hollow tubes)
Compare the function of xylem and phloem tissue.
Xylem tissue is involved in transpiration whereas phloem tissue is involved in translocation.
Both transport substances through the stems, leaves, and roots of a plant but where xylem tissue transports water and mineral ions, phloem tissue transports dissolved sugars.
Explain one way in which root hair cells are adapted for their function
Large surface area for faster/more osmosis.
Name three aseptic techniques a student should use (culturing microorganisms)
-sterilise equipment
-secure lid of petri dish with tape
-only lift lid of petri dish a little
Briefly describe stage 3 of the cell cycle
The cytoplasm AND cell membrane divides.
Why might a student not be able to see cells when looking down a microscope?
-no cells in the field of view
-slide not in the correct position
-lens dirty
When placed into a beaker of water, a red blood cell will burst but a plant cell will not. Explain why. [2]
Water enters the cells by osmosis.
The plant cell has a cell wall which prevents it from bursting.
What is a eukaryote?
An organism whose cells contain a nucleus and other membrane-bound organelles.
How is total magnification calculated?
Eyepiece lens x objective lens
How would we tell if a cell is prokaryotic?
If it’s genetic material is not contained within a nucleus.
Why is the electron microscope better than the light microscope for viewing subcellular structures?
-Has a better resolution so can distinguish between two points more easily, leading to a sharper image
-Has a higher magnification so can be used to see smaller objects
