BIOLOGY · FREE FLASHCARDS
Biology flashcards: cells, enzymes and DNA
Level: A-level Biology and first-year university
These free flashcards cover the cell biology that comes up in A-level Biology and first-year university courses: organelles, prokaryotic and eukaryotic cells, membranes, transport, enzymes and DNA replication. Read the front, say the answer out loud, then flip the card. Testing yourself like this is called active recall, and it beats re-reading.
How to use these flashcards
- Answer before you flip. Retrieving the answer is what makes it stick.
- Put the cards you got wrong back in the pile and repeat them later. This is spaced repetition.
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Flashcards
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- What does the nucleus do?
- Holds the cell's DNA as chromatin and controls the cell by directing protein synthesis. The nucleolus makes ribosomes.
- What happens in mitochondria?
- Aerobic respiration: the link reaction, the Krebs cycle and oxidative phosphorylation, which make most of the cell's ATP.
- 80S vs 70S ribosomes
- Both are sites of protein synthesis. Eukaryotic cytoplasm has larger 80S ribosomes; prokaryotes, mitochondria and chloroplasts have smaller 70S ribosomes.
- Rough vs smooth endoplasmic reticulum
- Rough ER is covered in ribosomes and folds and processes proteins. Smooth ER has no ribosomes and makes and processes lipids.
- What does the Golgi apparatus do?
- Modifies proteins (for example adding carbohydrates to make glycoproteins), packages them into vesicles for secretion, and makes lysosomes.
- Three differences between prokaryotic and eukaryotic cells
- Prokaryotes have no nucleus (circular DNA free in the cytoplasm, not bound to histones), no membrane-bound organelles, and smaller 70S ribosomes. Many also have a murein cell wall, plasmids and a capsule.
- The fluid mosaic model
- The membrane is a phospholipid bilayer with proteins scattered through it like a mosaic. Its molecules can move, so it is fluid. It also contains cholesterol (in animal cells), glycoproteins and glycolipids.
- Simple diffusion
- The net movement of small or lipid-soluble molecules from a higher to a lower concentration, straight through the phospholipid bilayer. It is passive: no ATP is needed.
- Facilitated diffusion
- Passive movement of larger or charged particles down a concentration gradient through channel or carrier proteins.
- Osmosis
- The net movement of water molecules from a region of higher water potential to a region of lower water potential, across a partially permeable membrane.
- Water potential of pure water
- 0 kPa, the highest possible value. Adding solutes makes water potential more negative.
- Active transport
- Movement of molecules or ions against a concentration gradient, using carrier proteins and energy from ATP.
- The induced fit model
- As the substrate binds, the active site changes shape slightly to fit it. This forms an enzyme-substrate complex, puts strain on bonds and lowers the activation energy.
- Why does high temperature stop enzymes working?
- Above the optimum, vibrations break hydrogen and ionic bonds in the tertiary structure. The active site changes shape, the substrate no longer fits, and the enzyme is denatured.
- Competitive vs non-competitive inhibitors
- Competitive inhibitors are a similar shape to the substrate and block the active site; adding more substrate reduces their effect. Non-competitive inhibitors bind elsewhere and change the active site's shape, so more substrate does not help.
- Semi-conservative replication
- Each new DNA molecule keeps one original strand and gains one new strand. DNA helicase breaks the hydrogen bonds between bases, free nucleotides pair with complementary bases, and DNA polymerase joins them.
Questions
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