Cell Biology
What's covered
Key facts
Cell Division
Cancer is uncontrolled cell division caused by mutations to genes that regulate the cell cycle, producing tumours.
Cell Structure
Animal cells do not have a cell wall (cellulose walls are a plant-cell feature).
Cell Transport
Active transport can move substances against a concentration gradient using cellular energy.
Microscopy
The main advantage of an electron microscope is far greater magnification and resolution than a light microscope.
Specialised Cells
Ciliated epithelial cells line the trachea and bronchi; their cilia sweep mucus and trapped debris away from the lungs.
Stem Cells
Adult stem cells are found in tissues like bone marrow and can differentiate into a more limited range of cell types — e.g. bone marrow stem cells form the various blood cell types but not nerves.
Cell Division
During meiosis, crossing over exchanges sections of chromatids between homologous chromosomes, creating new combinations of alleles.
Cell Structure
The cell membrane controls which substances enter and leave the cell.
Cell Transport
Active transport moves substances against a concentration gradient and requires energy.
Microscopy
Electron microscopes can see ribosomes and other tiny organelles that light microscopes cannot resolve.
Sample questions
A taste of the 72 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What type of cell division produces two genetically identical daughter cells for growth and repair?
- •Binary fission
- •Fertilisation
- •Meiosis
- ✓Mitosis
Which structure is found in plant cells but NOT in animal cells?
- •Cell membrane, cytoplasm, and a nucleus
- ✓Cell wall, chloroplasts, and a permanent vacuole
- •Cytoplasm, ribosomes, and a cell membrane
- •Mitochondria, ribosomes, and a nucleus
What is osmosis?
- •Any molecule moves down a concentration gradient through a membrane.
- •Mineral ions move through a membrane using ATP from mitochondria.
- •Water moves against its gradient using energy from respiration.
- ✓Water moves through a partially permeable membrane down its gradient.
What is the main advantage of an electron microscope?
- ✓Far greater magnification and resolution than a light microscope.
- •It can view living cells, while light microscopes cannot.
- •It is cheaper and easier to use in schools.
- •It produces colour images instead of black-and-white ones.
How is a sperm cell adapted for fertilising an egg?
- •Cilia for movement and glycogen stores instead of mitochondria.
- ✓Long tail to swim; mitochondria for energy; acrosome enzymes.
- •No cell membrane and no DNA, so it fuses easily.
- •Very large body with thick cell wall to protect DNA.
What is a stem cell?
- •A mature cell that has permanently lost the ability to divide.
- •A plant-only cell producing new growth at shoot and root tips.
- •A white blood cell that produces antibodies against pathogens.
- ✓An undifferentiated cell that can divide and specialise.
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