Name the structures found in a bacterial cell.
Reveal answer
Cell wall, cell membrane, cytoplasm, a circular chromosome of DNA, and plasmids. There is no nucleus.
Key words: circular chromosome · plasmid · cell wall
1(b) VARIETY OF LIVING ORGANISMS · RECALL
1.3 Common features of bacteria
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Give the two bacteria named in the specification and one fact about each.
Reveal answer
Lactobacillus bulgaricus: rod-shaped, used to make yoghurt from milk. Pneumococcus: spherical, causes pneumonia.
Key words: Lactobacillus · Pneumococcus
How do most bacteria feed, and how do a few feed differently?
Reveal answer
Most feed off other organisms, living or dead; a few can photosynthesise.
Key words: feed · photosynthesise
What is meant by the term prokaryote?
Reveal answer
An organism whose cell lacks a membrane-bound nucleus and other membrane-bound organelles.
Key words: prokaryote
What is meant by the term plasmid?
Reveal answer
A small circular DNA molecule separate from the main bacterial chromosome.
Key words: plasmid
What is meant by the term chromosome?
Reveal answer
The main DNA molecule carrying genes; bacterial chromosomes are usually circular.
Key words: chromosome
What is meant by the term flagellum?
Reveal answer
A rotating protein structure that moves some bacterial cells.
Key words: flagellum
What is meant by the term pathogen?
Reveal answer
A microorganism or infectious agent (including viruses) that causes disease.
Key words: pathogen
Reading a bacterial cell, Cell membrane. What it is? Why it matters?
Reveal answer
What it is: Boundary around the cytoplasm. Why it matters: Controls exchange and supports membrane-associated reactions.
Key words: Cell membrane
Reading a bacterial cell, Cytoplasm. What it is? Why it matters?
Reveal answer
What it is: Aqueous interior containing enzymes. Why it matters: Site of many metabolic reactions.
Key words: Cytoplasm
Reading a bacterial cell, Ribosomes. What it is? Why it matters?
Reveal answer
What it is: Small protein-making structures. Why it matters: Build proteins from amino acids.
Key words: Ribosomes
Reading a bacterial cell, Circular chromosome. What it is? Why it matters?
Reveal answer
What it is: Main loop of DNA free in the cytoplasm. Why it matters: Carries essential genetic information.
Key words: Circular chromosome
Reading a bacterial cell, Plasmid. What it is? Why it matters?
Reveal answer
What it is: Small additional ring of DNA. Why it matters: May carry transferable advantageous genes.
Key words: Plasmid
Reading a bacterial cell, Cell wall. What it is? Why it matters?
Reveal answer
What it is: Rigid layer outside the membrane. Why it matters: Supports the cell and helps prevent osmotic bursting.
Key words: Cell wall
True or false, and why? “Bacteria have no DNA because they have no nucleus.”
Reveal answer
False. Their circular chromosome and any plasmids lie free in the cytoplasm.
True or false, and why? “Bacteria cannot respire because they have no mitochondria.”
Reveal answer
False. They carry out respiratory reactions in the cytoplasm and across cell membranes.
True or false, and why? “Photosynthetic bacteria contain chloroplasts.”
Reveal answer
False. They use pigments and membrane systems but do not possess chloroplast organelles.
True or false, and why? “All bacteria are pathogens.”
Reveal answer
False. Only some cause disease; many are harmless or beneficial.