Cell Structure Flashcards
All 37 cards in this deck
What is the function of the nucleus in an animal or plant cell?
It contains the chromosomal DNA and controls the activities of the cell.
What is the function of mitochondria?
They are where aerobic respiration takes place, releasing energy (producing ATP).
What is the function of ribosomes?
Protein synthesis — they are where proteins are made.
What is the plant cell wall made of, and what does it do?
Cellulose; it is strong and rigid, giving the cell support and stopping it bursting.
What is the function of the permanent vacuole in a plant cell?
It holds cell sap; as water enters, the cell becomes turgid, which supports the cell.
Which three structures are found in plant cells but not in animal cells?
Cell wall, chloroplasts and a large (permanent) vacuole.
What is the characteristic feature of a prokaryotic cell?
It has no nucleus — its chromosomal DNA lies free in the cytoplasm.
What is plasmid DNA?
A small circular loop of DNA in a bacterial cell, separate from the chromosomal DNA.
What is the function of a bacterial flagellum?
It moves the cell (motility); a bacterium without flagella, e.g. Streptococcus, is not motile.
True or false? Bacterial cells do not have ribosomes.
False. Bacteria do have ribosomes; what they lack is membrane-bound organelles such as mitochondria and chloroplasts.
Why are the cells of organisms such as birds described as eukaryotic?
They have membrane-bound organelles, including a nucleus.
What is the function of the acrosome in a sperm cell?
It contains digestive enzymes that break through the membrane of the egg cell.
Why does a sperm cell contain many mitochondria?
To release energy by respiration so the tail can move the sperm to the egg.
True or false? The nucleus of a sperm cell is haploid.
True. It carries one set of chromosomes, so the fertilised egg has the full number.
What does the cytoplasm of an egg cell contain, and why?
Nutrients — a food store for the developing embryo.
What happens to the membrane of an egg cell straight after fertilisation?
It changes (hardens) so that no other sperm can enter.
What is the function of ciliated epithelial cells in the airways?
Their cilia waft mucus (containing trapped dust and bacteria) away from the lungs.
What is the equation linking magnification, image size and actual size?
magnification = image size ÷ actual size
What is meant by the resolution of a microscope?
The smallest distance between two points that can still be seen as two separate points.
Why is an electron microscope used to see mitochondria clearly rather than a light microscope?
It has greater magnification and greater resolution (electron beams have a shorter wavelength).
True or false? Ribosomes can be seen using a light microscope.
False. A light microscope has too low a resolution; ribosomes were only seen once electron microscopes were developed.
What is the equation for the total magnification of a light microscope?
total magnification = eyepiece lens magnification × objective lens magnification
Why is a coverslip placed on a microscope slide?
To keep the specimen flat and in place, and to protect the specimen and the objective lens.
Why is a stain added when preparing a slide of cells?
To make the cells and their structures show up clearly (increase contrast) so they can be identified.
Why is a thin peel or thin section viewed under a light microscope rather than the whole specimen?
The whole specimen is too thick and would not let light pass through it; a thin section lets light through so the cells can be identified.
What should a labelled scientific drawing of cells seen under a microscope include?
Clear sharp pencil lines with no shading, the shape of the actual cells seen, labels (e.g. nucleus, cytoplasm, cell membrane, cilia) and the magnification or a scale bar.
What does the prefix milli (m) mean?
One thousandth, .
e.g. 1 mm = mWhat does the prefix micro (µ) mean?
One millionth, .
e.g. 1 µm = mWhat does the prefix nano (n) mean?
One thousand-millionth, .
e.g. 1 nm = mWhat does the prefix pico (p) mean?
(one million-millionth).
e.g. 1 pm = mTrue or false? 6000 µm written in standard form is µm.
False. It is µm — a negative power is only used for numbers smaller than 1.
When should an estimate be used instead of an exact measurement or count?
When measuring or counting everything exactly is impractical, e.g. counting the cells in one field of view and scaling up to estimate the total.
True or false? The cell wall of a bacterial cell is made of cellulose.
False. Bacteria do have a cell wall, but it is not made of cellulose — cellulose cell walls are found in plant cells.
What is the function of the cell membrane?
It surrounds the cell and controls which substances can enter and leave it.
What kind of genes can plasmids carry, and how can they spread?
Extra genes, such as genes for antibiotic resistance; plasmids can be passed from one bacterium to another.
Which type of microscope can be used to look at living cells: a light microscope or an electron microscope?
A light microscope. Specimens for an electron microscope cannot be alive.
When first bringing a slide into focus under a light microscope, which objective lens and which focusing knob should you use?
The lowest-power objective lens and the coarse adjustment knob; then use the fine adjustment knob to make the image sharp.