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Cheatography

life processes Y9 Cheat Sheet (DRAFT) by

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
 
between solid-­liquid (texture)
 
made of many struct­ures, can be seen in an electron microscope
 
structures -> organelles
Nucleus:
largest organelle
Contains:
chromo­somes (carry genes)
 
important group of proteins:enzymes (control the chemical reactions in the cytoplasm)
Cell membrane:
thin layer
 
forms a boundary between cytopl­asm­-ou­tside
 
chemicals can pass into and out -> membrane is partially permeable
 
can go further & control the movement-select­ively permeable
Mitoch­ond­rion:
need a lot of energy (muscl­e/nerve cells)
 
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
 
made of cellulose (carbo­hyd­rate) -> helps the cell to keep its shape
Vacuole:
large central space surrounded by a membrane
 
permanent feature of the cell
 
filled w/ cell sap (store of dissolved sugars, mineral ions and other solutes)
Chloro­plast:
absorbs light energy to make food (photo­syn­thesis)
 
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
 
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

enzyme catalysing

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

pH figure

 

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
------­---­---­---­---­---­---­---­---­---­------
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