Cells and Microscopy Flashcards
State the two types of cell
Eukaryotic (animals and plants) and prokaryotic
What is the difference between a eukaryotic and prokaryotic cell?
A eukaryotic cell contains a nucleus and membrane-bound organelles. A prokaryotic cell does not.
List the components of both plant and animal cells (5)
● Nucleus ● Cytoplasm ● Cell membrane ● Mitochondria ● Ribosomes
How is genetic information stored in a eukaryotic cell?
Within the nucleus, arranged in chromosomes
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 e.g. first stage of respiration
What is the function of the cell membrane?
Controls the entry and exit of materials 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?
Where protein synthesis occurs
Which organelles are found in plant cells only? (3)
● Large, permanent vacuole
● Cell wall
● Chloroplasts
What is the plant cell wall made of?
Cellulose
What is the function of the cell wall?
● Provides strength
● Prevents the cell bursting when water enters by osmosis
What does the permanent vacuole contain?
A solution of salts, sugars and organic acids
What is the function of the permanent vacuole?
Supports the cell, maintaining its turgidity
What is the function of the chloroplasts?
Site of photosynthesis
When looking at a cell using a light microscope, why do chloroplasts appear green?
Contain chlorophyll, a green pigment
List the organelles found in prokaryotic cells (6)
● Chromosomal DNA ● Plasmid DNA ● Cell wall ● Cell membrane ● Ribosomes ● Flagella
How is genetic information stored in a prokaryotic cell?
Found free within the cytoplasm as:
● 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 e.g. antibiotic resistance
What is the prokaryotic cell wall composed of?
Peptidoglycan
What is a flagellum?
● Long, rotating, ‘whip-like’ protrusion
● Enables bacteria to move
What is a haploid cell?
A cell that contains a single copy of each chromosome (half the number of chromosomes)
e.g. 23 chromosomes in humans
What is a diploid cell?
A cell that contains two copies of each chromosome (full set of chromosomes)
e.g. 46 chromosomes in humans
What are gametes?
● Reproductive cells(e.g.egg and sperm cells)
● They are haploid cells
Describe sexual reproduction in terms of chromosome number
● Two haploid gametes fuse
● Resulting embryo has two chromosomes for each gene and two copies of each allele ∴ diploid
Describe how egg cells are adapted to their function
● Haploid nucleus contains genetic material
● Mitochondria in cytoplasm produce energy for the developing
embryo
● Cytoplasm contains nutrients for the developing embryo
● Cell membrane hardens after fertilisation, preventing the entry of other sperm and ensuring the zygote is diploid
Describe how sperm cells are adapted to their function
● Haploid nucleus contains genetic information (23 chromosomes)
● Streamlined head and flagellum (tail) enables movement
● Mitochondria provide energy for tail movement
● Acrosome contains enzymes that digest the egg cell membrane
Where are ciliated epithelial cells found?
Found lining the surface of structures such as the respiratory tract and uterus.
Describe the function of ciliated epithelial cells lining the airways
Move in synchronised waves to beat mucus (containing dirt and pathogens) up to the back of the throat where it can be swallowed.
What is magnification?
The number of times bigger an image appears compared to the size of the specimen
How can the total magnification of an image be calculated from lens powers?
Total magnification = eyepiece lens magnification x objective lens magnification
How can the magnification of an image be calculated?
Magnification = size of image/size of specimen
What is resolution?
The smallest distance between two objects that can be distinguished
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.
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 types 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 (e.g. mitochondria, ribosomes) 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 do you convert from m to mm?
× 10^3
How do you convert from m to μm?
x 10^6
How do you convert from m to nm?
x 10^9
How to you convert from nm to m?
x 10^-9
How do you convert from m to pm?
x 10^12
Write 0.005 in standard form
5 x 10^-3
Write 10382 in standard form
1.0382 x 10^4
Convert 1.527 m to μm. Write your answer in standard form
1.527 x 10^6 μm
