Cell Structure Flashcards
All 37 cards in this deck
What is the function of the nucleus in an animal or plant cell?
It controls the activities of the cell. It contains the chromosomes (DNA/genes).
What is the function of the cell membrane?
It controls which substances enter and leave the cell.
What is the function of mitochondria?
Aerobic respiration – they release energy. Say 'release energy', never 'make energy'.
What is the function of ribosomes?
Protein synthesis – this is where proteins are made.
Which three structures are found in plant cells but not in animal cells?
Cell wall, chloroplast and large (permanent) vacuole.
What is a plasmid?
A small ring of DNA in a bacterial cell, separate from the chromosomal DNA.
What is the function of a bacterial flagellum?
Movement – it allows the bacterium to swim.
True or false? A bacterial cell keeps its chromosomal DNA inside a nucleus.
False. Bacteria have no nucleus – the chromosomal DNA is a single loop free in the cytoplasm.
Give three structures found in both a bacterial cell and a plant cell.
Cell wall, cell membrane and ribosomes (also cytoplasm and DNA).
Which cells are prokaryotic and which are eukaryotic?
Bacteria are prokaryotic; animal and plant cells are eukaryotic. Prokaryotic cells are also much smaller.
What is the acrosome of a sperm cell and what does it do?
A sac of enzymes in the head; the enzymes digest the membrane around the egg so the sperm can enter.
Why does a sperm cell have many mitochondria?
To release energy by respiration so the tail can move and the sperm can swim to the egg.
What does it mean that the nucleus of a sperm cell or egg cell is haploid?
It contains half the number of chromosomes of a body cell – 23 in a human gamete.
Why does the cytoplasm of an egg cell contain nutrients?
To provide food for the developing embryo after fertilisation.
What happens to the cell membrane of an egg cell straight after fertilisation?
It changes so that no more sperm can enter the egg.
How are ciliated epithelial cells in the airways adapted to their function?
They have cilia that beat to move (waft) mucus, with trapped dust and bacteria, along the airway.
What is meant by the resolution of a microscope?
The smallest distance between two points that can still be seen as two separate points.
Give two advantages of an electron microscope over a light microscope.
Higher resolution and higher magnification, so more detail and smaller structures can be seen.
Give two advantages of a light microscope over an electron microscope.
It is affordable and easy to use (also portable, large field of view, shows colour and living cells).
What can electron microscopes show scientists that light microscopes cannot?
Small sub-cellular structures such as ribosomes and the inside of mitochondria, which revealed what these organelles do.
Why is a stain such as iodine added to a slide of onion cells?
To make the cells and their structures, such as the nucleus, more visible.
Why must the specimen on a microscope slide be a thin layer of cells?
So that light can pass through it, so the cells can be seen clearly.
What equation gives the total magnification of a light microscope?
total magnification = eyepiece lens magnification × objective lens magnification
What equation links the actual size of a cell, its image size and the magnification?
actual size = image size ÷ magnification
What should a labelled scientific drawing of a cell seen under a microscope show?
The shape and internal structures of the cell you actually observed, with parts labelled (e.g. nucleus, cytoplasm, cell membrane) – not a copied textbook diagram.
Which part of a light microscope do you adjust to get a clear image?
The focusing wheel (which moves the stage or lens up and down); the mirror or lamp is adjusted for brightness.
What does the prefix milli mean?
10⁻³ (one thousandth). e.g. 1 mm = 0.001 m
What does the prefix micro mean?
10⁻⁶ (one millionth). e.g. 1 µm = 0.000001 m
What do the prefixes nano and pico mean?
nano = 10⁻⁹ and pico = 10⁻¹².
How many micrometres (µm) are there in 1 millimetre (mm)?
1 000
Which unit is normally used to give the size of animal cells?
The micrometre (µm) – a typical animal cell is about 10–20 µm across.
True or false? Plant cells do not contain mitochondria because they have chloroplasts instead.
False. Plant cells contain both: chloroplasts for photosynthesis and mitochondria for respiration.
True or false? A nanometre is larger than a micrometre.
False. A nanometre is m and a micrometre is m, so a nanometre is 1000 times smaller.
What is the function of chloroplasts in a plant cell?
Photosynthesis – they contain chlorophyll, which absorbs light.
What is the function of the cell wall in a plant cell?
It supports and strengthens the cell. It is made of cellulose.
What is the function of the vacuole in a plant cell?
It contains cell sap and keeps the cell firm (turgid).
Give two rules to follow when making a scientific drawing of a specimen seen under a microscope.
Any two: use single, clear, unbroken pencil lines; don't colour or shade; rule label lines straight and don't let them cross; record the magnification or a scale.