Cheatography
https://cheatography.com
i hate biology, but i have to learn it
This is a draft cheat sheet. It is a work in progress and is not finished yet.
CELL STRUCTURE
Cytoplasm: |
Living material that makes up a cell |
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between solid-liquid (texture) |
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made of many structures, can be seen in an electron microscope |
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structures -> organelles |
Nucleus: |
largest organelle |
Contains: |
chromosomes (carry genes) |
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important group of proteins:enzymes (control the chemical reactions in the cytoplasm) |
Cell membrane: |
thin layer |
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forms a boundary between cytoplasm-outside |
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chemicals can pass into and out -> membrane is partially permeable |
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can go further & control the movement-selectively permeable |
Mitochondrion: |
need a lot of energy (muscle/nerve cells) |
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carry out reactions of respiration |
- The DNA stays in the nucleus, proteins are carried to the cytoplasm, they are put together in ribosomes.
PLANT CELLS
Cell wall: |
layer of non-living material outside the cell membrane |
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made of cellulose (carbohydrate) -> helps the cell to keep its shape |
Vacuole: |
large central space surrounded by a membrane |
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permanent feature of the cell |
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filled w/ cell sap (store of dissolved sugars, mineral ions and other solutes) |
Chloroplast: |
absorbs light energy to make food (photosynthesis) |
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contains chlorophyll (green pigment) |
ENZYMES: CONTROLLING REACTIONS IN THE CELL
- Chemical reactions are controlled by enzymes |
- Enzymes are biological catalysts |
- Catalysts: chemical which speeds up a reaction w/out being used up itself |
- It takes part in the reaction, but then is unchanged and free to catalyse more |
- Cells contain many different enzymes, each catalysing different reactions |
genes -> proteins (enzymes) -> catalyse reactions |
KEY POINT
Metabolic reactions: chemical reactions in a cell |
Metabolism: sum of all the metaboloic reactions |
Enzymes' function: catalyse these reactions |
KEY POINT 2
In the intestine enzymes are covered onto the food to break it down -> extracellular enzymes (outside cells) |
However, most enzymes stay inside cells and do their function there -> intracellular |
KEY POINT 3
Secretion is the release of fluid/substances from a cell/tissue |
Why are enzymes important?
- The temperatures inside the organisms are low |
e.g-> human 37ºC, w/out catalysts the reactions would be too slow to allow life to go on |
- Reactions only take place quickly enough when enzymes are ther to speed them up |
ENZYMES 2
Substrate: |
molecule that an enzyme acts on |
Active site: |
small area on an enzyme's surface |
Lock and key model: |
the substrate fits into the active site of the enzyme like a key fitting into a lock |
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a substrate will only fit into the active site of a particular enzyme |
1- the substrate attaches to the active site of the enzyme
2- the reaction the takes place and products are formed
3- substrate joins up w/ the active site -> lowers the energy needed for the reaction to start, allowing the products to be formed easily
TEMPERATURE
As the enzyme is heated up to the optimum temperature, the rise in temperature increases the rate of reaction. |
↑ temperatures give the enzyme's molecules & substrate + kinetic energy -> they collide more often |
+ collisions -> reaction will take place more frequently |
KEY POINT
"Optimum" temperature means the "best" temperature (temperature at which the reaction takes place most rapidly)
TEMPERATURE 2
However, above the optimum, temperature has another effect |
Enzymes are made of proteins-> proteins are broken down by heat |
Denatured: ↑40ºC, heat destroys the enzyme |
Denaturing changes the shape of the active site so the substrate won't fit into it |
Denaturing's permanent- enzyme molecules won't catalyse the reaction |
effect of t on the action of an enzyme
pH
pH's inside cells is neutral (pH7) & most enzymes have evolved to work best at this pH. |
at extremes of pH either side of neutral, the enzyme activity decreases (photo) |
optimum pH: pH at which the enzyme works best |
either side of the optimum, the pH affects the structure of the enzyme molecule & changes the shape of its active site-> substrate won't fit into it so well |
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HOW THE CELL GETS ITS ENERGY
how does it get energy? ↓ |
respiration: break down food molecules to release the stored chemical energy that they contain |
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oxygen: oxidise food |
carbon dioxide & water: are released as waste products |
glucose (sugar):main food oxidised, contains stored chemical energy that can be converted into other forms of energy |
respiration releases ATP, can be used in ↓ |
-contraction of muscle cells (movement) |
- active transport of molecules and ions |
- building large molecules (proteins) |
- cell division |
reaction for respiration ↓↓ |
glucose + oxygen -> carbon dioxide + water (+energy) |
C6H12O6 + 6O2 -> 6CO2 + 6H2O |
⌙-> aerobic respiration |
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