Biology Year 9

Plant & animal cells > eukaryotic cells 

• cell membrane
• cytoplasm
• genetic material enclosed within nucleus

Bacteria cells > prokaryotic cells 

• much smaller
• cytoplasm
• cell mebrane
• cell wall
• genetic material not enclosed (single DNA loop with (sometimes) one or more small rings of DNA called plasmids

Most types of animal cells differentiate at a young age

Mant plant cells can differntiate throughout life

Cell differentation = specialised cell

Electron microscope:

• higher magnification & resolving power
• more expensive
• allows scientists to study cells in higher detail than light microscope

Cells are basic building blocks 

Tissue > group of cells with simular function

Organs > aggregation of tissues performing specific functions

Organ systems > work to form organisms

Eg. circulatory, nervous, repoductive, digestive

• Have an active site specific to one molecule (lock & key)
• If damaged (pH, temperature) enzyme is denatured

Optimum temp > 37........ Optimum pH varies for each enzyme

Enzymes are catalysts > speed up reaction but remain unchanged

Bile > made in liver (stored in gall bladder) alkaline used to neutralise acid from stomach entering small intestine

       > also emulsifies fat to form small droplets (larger surface area) - increases rateit can be broken down at

Stomach contains hydrochloric acid > kills bacteria & correct conditions for stomach enzymes

Bile > made in liver (stored in gall bladder) alkaline used to neutralise acid from stomach entering small intestine

       > also emulsifies fat to form small droplets (larger surface area) - increases rateit can be broken down at

Stomach contains hydrochloric acid > kills bacteria & correct conditions for stomach enzymes

Small intestine > food is absorbed into blood stream through villi & micro villi 

Large intestine > excess water is absorbed 

Glucose + oxygen > CO2 + water (+ energy)

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Respiration supplies energy needed for:

• chemical reactions to build larger molecules
• movement
• keeping warm

Happens in muscles, plants & yeast

In yeast > known as fermentation (used for bread making & alcoholic drinks)

glucose → ethanol + carbon dioxide (+ energy released)

In muscles > produces less energy than aerobic & causes oxygen debt

glucose → lactic acid (+ energy released)

During exercise:

• heart rate increases
• breathing rate increases
• breath volume increases

If there is not enough oxygen anaerobic respiration takes place

Oxygen debt > the amount of extra oxygen the body needed after exercise to react with the lactic acid & remove it from the cells

After exercise:

• blood flowing through muscles transports lactic acid to liver
• convertes back to glucose

Sum of all the chemical reactions in a cell or body

Metabolism includes:

• conversion of glucose to starch, gycogen & cellulose
• formation of lipid molecules from a molecule of glycerol & three molecules of fatty acids
• glucose & nitrate ions tp form amino acids which synthesise proteins
• respiration
• breakdown of excess proteins to form urea for excretion

Anabolic reaction > makes up eg. phtosynthesis

Catabolic > breaks down eg. digestion

Oxygen goes throught trachea > bronchi > bronchioles > alveoli

CO2 & oxygen diffuse (high concentration to low concentration) into & out of the alveoli into the blood stream