A Level Terms

Phosphorylation

The transfer of phosphate atoms from ATP to glucose to raise its energy level.

-2 ATP; +4 ATP; +2 NADH

Product of glycolysis

Substrate-linked phosphorylation

Is a process in which ATP is produced by the direct transfer of a phosphate group to ADP from a substrate molecule during glycolysis.

Decarboxylation

The removal of carbon dioxide.

Dehydrogenation

The removal of hydrogen

Acetyl Coenzyme A

The compound formed during the link reaction

+1 CO2; +1 NADH

Product of link reaction

+3 NADH; +2 CO2; +1 GTP (ATP); +1 FADH2

Product of Kerbs cycle

Citrate

Starting product of the Krebs cycle

Oxaloacetate

Ending product of the Kerbs cycle

redox reaction

a chemical reaction in which one substance is reduced and another is oxidised

-2 ATP; +34 ATP; +6 H2O; +6 CO2

Total production from respiration

Ethanol fermentation

Anaerobic respiration in which pyruvate is converted to ethanol

Lactate fermentation

Anaerobic respiration in which pyruvate is converted to lactate

Aerenchyma

plant tissue containing air spaces

respiratory quotient (RQ)

the ratio of the volume of carbon dioxide produced to the volume of oxygen used. Volume of CO2 given out/Volume of oxygen taken in.
- Carbs: 1.0
- Lipids 0.7

- Proteins: 0.9

- Anaerobic: more than 1

Photolysis

splitting a water molecule, using energy from light

Photophosphorylation

producing ATP using energy that originated as light

Stroma

the background material in a chloroplast in which the light-independent stage of photosynthesis takes place

Lamellae

membranes found within a chloroplast

Thylakoid spaces

fluid-filled sacs enclosed by the thylakoid membranes

Thylakoid membranes

the membranes inside a chloroplast that enclose fluid-filled sacs; the light dependent stage of photosynthesis takes place in these membranes

Grana

Stacked thylakoids

P680

Photosystem II absorption range

P700

Photosystem I absorption range

photoactivation

the emission of an electron from a molecule as a result of the absorption of energy from light

cyclic photophosphorylation

the production of ATP using energy from light, involving only photosystem I

non-cyclic photophosphorylation

the production of ATP using energy from light, involving both photosystem I and photosystem II; this process also produces reduced NADP

ribulose bisphosphate (RuBP)

a five-carbon phosphorylated sugar which is the first compound to combine with carbon dioxide during the light-independent stage of photosynthesis

Rubisco

the enzyme that catalyses the combination of RuBP with carbon dioxide

glycerate-3-phosphate (GP) (G3P)

a three-carbon compound which is formed when RuBP combines with carbon dioxide

triose phosphate (TP)

a three-carbon phosphorylated sugar, the first carbohydrate to be formed during the light-independent stage of photosynthesis

-1 NADPH; -2 ATP

A turn of the Calvin cycle

Photosynthesis limiting factors

• The presence of photosynthetic pigments

• a supply of carbon dioxide

• a supply of water

• light energy

• a suitable temperature

Deamination

the breakdown of excess amino acids in the liver, by the removal of the amine group; ammonia and, eventually, urea are formed from the amine group

nephron

the structural and functional unit of the kidney composed of Bowman’s capsule and a tubule divided into three regions: proximal convoluted tubule, loop of Henle and distal convoluted tubule

Bowman’s capsule

the cup-shaped part of a nephron that surrounds a glomerulus and collects f iltrate from the blood

glomerulus

a group of capillaries within the ‘cup’ of a Bowman’s capsule in the cortex of the kidney

proximal convoluted tubule

part of the nephron that leads from Bowman’s capsule to the loop of Henle

loop of Henle

the part of the nephron between the proximal and distal convoluted tubules

distal convoluted tubule

part of the nephron that leads from the loop of Henle to the collecting duct

collecting duct

tube in the medulla of the kidney that carries urine from the distal convoluted tubules of many nephrons to the renal pelvis

afferent arteriole

arteriole leading to glomerular capillaries

efferent arteriole

arteriole leading away from glomerular capillaries

ultrafiltration

filtration on a molecular scale separating small molecules from larger molecules, such as proteins (e.g. the filtration that occurs as blood flows through capillaries, especially those in glomeruli in the kidney)

selective reabsorption

movement of certain substances from the filtrate in nephrons back into the blood

Podocyte

one of the cells that makes up the lining of Bowman’s capsule surrounding the glomerular capillaries

Cuboidal epithelial cells

Nephron cells

antidiuretic hormone (ADH)

hormone secreted from the posterior pituitary gland that increases water reabsorption in the kidneys and therefore reduces water loss in urine

osmoregulation

the control of the water potential of blood and tissue fluid by controlling the water content and/or the concentration of ions, particularly sodium ions

osmoreceptor

type of receptor that detects changes in the water potential of blood

islets of Langerhans

a group of cells in the pancreas which secrete glucagon and insulin

glucagon

a small peptide hormone secreted by the α cells in the islets of Langerhans in the pancreas to bring about an increase in the concentration of glucose in the blood

insulin

a small peptide hormone secreted by the β cells in the islets of Langerhans in the pancreas to bring about a decrease in the concentration of glucose in the blood

glycogenesis

synthesis of glycogen by addition of glucose monomers

adenylyl cyclase

enzyme that catalyses formation of the second messenger cyclic AMP

Protein kinase A

enzyme that is activated by c-AMP and once activated adds phosphate groups to other proteins, including phosphorylase kinase, to activate them

Phosphorylase kinase

an enzyme that is part of the enzyme cascade that acts in response to glucagon; the enzyme activates glycogen phosphorylase by adding a phosphate group

glycogenolysis

the breakdown of glycogen by removal of glucose monomers

gluconeogenesis

the formation of glucose in the liver from non-carbohydrate sources such as amino acids, pyruvate, lactate, fatty acids and glycerol

abscisic acid (ABA)

an inhibitory plant growth regulator that causes closure of stomata in dry conditions

sensory neuron

a neuron that transmits nerve impulses from a receptor to the central nervous system (CNS)

intermediate neurons

neurons that transmit impulses from sensory neurons to motor neurons

motor neurons

transmit impulses from the CNS to effectors

myelin

insulating material that surrounds the axons of many neurons; myelin is made of layers of cell surface membranes formed by Schwann cells so that they are very rich in phospholipids and therefore impermeable to water and ions in tissue fluid

node of Ranvier

a very short gap between Schwann cells where myelinated axons are not covered in myelin so are exposed to tissue fluid

Schwann cells

Cells that surround the axons of some neurons

action potential

a brief change in the potential difference from –70 mV to +30 mV across the cell surface membranes of neurons and muscle cells caused by the inward movement of sodium ions

resting potential

the difference in electrical potential that is maintained across the cell surface membrane of a neurone when it is not transmitting an action potential; it is normally about –70 mV inside and is partly maintained by sodium–potassium pumps

potential difference

the difference in electrical potential between two points; in the nervous system, between the inside and the outside of a cell surface membrane such as the membrane that encloses an axon

voltage-gated channel protein

a channel protein through a cell membrane that opens or closes in response to changes in electrical potential across the membrane

depolarisation

the reversal of the resting potential across the cell surface membrane of a neuron or muscle cell, so that the inside becomes positively charged compared with the outside

Threshold potential

the critical potential difference across the cell surface membrane of a sensory receptor or neuron which must be reached before an action potential is initiated

Repolarisation

returning the potential difference across the cell surface membrane of a neuron or muscle cell to normal following the depolarization of an action potential

refractory period

a period of time during which a neurone is recovering from an action potential, and during which another action potential cannot be generated

Saltatory conduction

movement of an action potential along a myelinated axon, in which the action potential ‘jumps’ from one node of Ranvier to the next

chemoreceptor

a receptor cell that responds to chemical stimuli; chemoreceptors are found in taste buds on the tongue, in the nose and in blood vessels where they detect changes in oxygen and carbon dioxide concentrations

receptor potential

a change in the normal resting potential across the membrane of a receptor cell, caused by a stimulus