Edexcel Biology Unit 5 Key Word Glossary

Negative Feedback - the system which maintains a condition in the body within a narrow range by detecting and counteracting a change bringing the level back to normal. 

Receptors - used to detect deviations from the norm.

Effector - carries out response which brings about a corrective change. 

Homeostasis - the maintenance of a stable internal environment.

Thermoregulation - temperature control in the body, controlled by the Hypothalamus. 

Respirometer - a piece of equipment that measures the rate of oxygen being taken up by an organism and therefore the rate of respiration. 

Glycolysis - the first stage of respiration, the ‘splitting of sugar’. Takes place in the cytoplasm. 

Phosphorylation - The addition of phosphate molecules to a glucose molecule to increase its reactivity, produces TP. Catalysed by Phosphofructokinase. 

Oxidation - the removal of H⁺ ion from TP to form pyruvate. 

Skeletal muscle - muscles which allow us to move, under the control of the voluntary nervous system, attached to bones. 

Myofibrils - long, cylindrical organelles within each muscle fibre, made up of proteins which are highly specialised for contraction. 

Sarcomere - units which make up a myofibril made up of actin and myosin. 

Sarcolemma - the cell membrane of muscle fibres. 

Sarcoplasm - the cytoplasm of the muscle cells. 

Sarcoplasmic Reticulum - a network of internal membranes which runs through the sarcoplasm, stores and released Ca²⁺ ions that are needed for muscle contraction. 

Myosin - thick myofilaments that appear dark under a microscope (A bands). 

Myosin Heads - globular head on the myosin which is hinged so it can move back and forth. Has a binding site for actin and ATP. 

Actin - thin myofilaments that appear light under a microscope (I bands). Have actin-myosin binding sites.

Tropomyosin & Troponin - Two proteins that are found between actin filaments, they are attached to each other and help myofilaments move past each other. 

Cross-Bridges - form when myosin heads bind with myosin binding sites on the actin. 

Slow Twitch Muscle Fibres - muscle fibres which are adapted for steady action over a period of time, which contract relatively slowly.

Fast Twitch Muscle Fibres - muscle fibres which are adapted for rapid bursts of activity, which contract very rapidly. 

Cartilage - found between bones, a good shock absorber, hard but flexible, elastic and able to withstand compressive forces. 

Tendons - join muscle to bone, gives a secure…