What do cells make up?
All living things
Name the two types of cell?
Eukaryotic
Prokaryotic
What are eukaryotic cells?
They’re complex and include all animal and plant cells.
What are prokaryotic cells?
They’re smaller and simpler than eukaryotic cells (e.g - bacteria)
What are Eukaryotes?
They’re organisms that are made up of eukaryotic cells.
What are prokaryotes?
They’re prokaryotic cells. (Single-called organisms).
What sub-cellular structures do most animal cells have?
- Nucleus - contains genetic material that controls the activities of the cell. Genetic material is arranged into chromosomes.
- Cytoplasm - gel-like substance where most of the chemical reactions happen. It contains enzymes that control these reactions.
- Cell membrane - holds the cell together and controls what goes in and out.
- Mitochondria - these are where most of the reactions fro respiration take place. Respiration transfers energy that the cell need to work.
- Ribosomes - these are involved in the translation of genetic material in the synthesis of proteins.
What sub-cellular structures do most plant cells have?
They usually have all the bits the animal cells have plus extra :
- Nucleus 2. Cytoplasm 3. Cell membrane 4. Mitochondria 5. Ribosomes
- Cell wall - made of cellulose. It supports the cell and strengthens it.
- Large vacuole - contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.
- Chloroplasts - these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.
What sub-cellular structures do most bacterial cells have?
- Chromosomal DNA - controls the cells activities and replication. It floats free in the cytoplasm.
- Ribosomes 3. Cell membrane
- Plasmid DNA - small lops of extra DNA that aren’t part of the chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria.
- Flagellum - a long hair-like structure that rotates to make the bacterium move. It can be used to move the bacteria away from harmful substances like toxins and towards beneficial things like nutrients or oxygen.
What’s the difference between bacterial cells and plant + animal cells?
Bacterial cells are a lot smaller and contain chromosomal DNA, flagellum and plasmid DNA.
What are multicellular organisms?
They contain lots of different types of cells (cells with different structures).
What are specialised cells?
They’re cells that have a structure which makes them adapted to their function.
E.g - egg, sperm and ciliated cells.
How is an egg cell adapted to its function?
The main functions of an egg are to carry the female DNA and to nourish the developing embryo in the early stages.
- It contains nutrients in the cytoplasm to feed the embryo.
- It has a haploid nucleus.
- Straight after fertilisation, its membrane changes structure to stop any more sperm getting in. This makes sure the offspring end up with the right amount of DNA.
How is a sperm cell adapted to its function?
The function of a sperm is to transport the males DNA to the females egg.
- A sperm cell has a long tail so it can swim to the egg.
- It has lots of mitochondria in the middle section to provide the energy (from respiration) needed to swim this distance.
- It also has an acrosome at the front of the ‘head’, where it stores enzymes needed to digest its way through the membrane of an egg cell.
- It also contains a haploid nucleus.
How is a ciliated epithelial cell adapted to its function?
They’re specialised for moving materials.
- Epithelial cells line the surfaces of organs.
- Some of them have cilia (hair-like structures) on the top surface of the cell.
- The cilia beta to move substances in one direction, along the surface of the tissue.
What’s the calculation for magnification?
Magnification = image size
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Real size
What are enzymes?
They’re catalysts produced by living things.
What is an active site?
Every enzyme has an active site.
The part where it joins on to its substrate to catalyse the reaction.
What’s the substrate?
It’s the molecule changed in the reaction.
Explain how enzymes work with substrates?
They usually only work with one substrate. They’re said to have high specificity for their substrate.
This is because, for the enzyme to work, the substrate has to fit into the active site. If the substrates shape doesn’t match the active sites shape, then the reaction wont be catalysed. This is called the lock and key mechanism, because the substrate fits into the enzyme just like a key fits into a lock.
What affects the rate of reaction?
Temperature, pH, substrate concentration.
How does changing the temperature, change the rate of an enzyme-catalyst reaction?
- A higher temperature increase the rate at first. But if it gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzymes active site, so the substrate won’t fit any more.
The enzyme is said to have been denatured.
- All enzymes have an optimum temperature that they work bets at.
How does changing the pH, change the rate of an enzyme-catalyst reaction?
- If it’s too high or low, the pH interferes with the bonds holding the enzymes together. This changes the shape of the active site and dentures the enzymes.
- All enzymes have an optimum pH that they work best at. It’s often neutral pH 7, but not always.
How does changing the substrate concentration, change the rate of an enzyme-catalyst reaction?
- The higher the concentration, the faster the reaction. This is because its more likely that the enzyme will meet up and react with a substrate molecule.
- This is only true up to a certain point. After that, there are so many substrate molecules that the enzymes have about as much as they can cope with, so adding makes no difference.
