OCR A level biology content

Excretion

The removal of waste products of metabolism from the body

Liver

A large lobed glandular organ in the abdomen of vertebrates, involved in many metabolic processes

Urea

A colourless compound which is the main nitrogenous breakdown product of protein metabolism in mammals and is excreted in urine

Hepatic Vein

The blood vessel that drains deoxygenated blood from the liver

Hepatic Artery

The blood vessel that supplies oxygenated blood to the liver

Hepatic Portal Vein

The blood vessel that conveys blood to the liver from the spleen, stomach, pancreas, and intestines

Hepatocyte

A liver cell

Liver Lobule

A polygonal unit of the liver consisting of masses of liver cells arranged around a central vein

Sinusoids

Small irregular shaped blood vessels found in the liver that run from the outside to the inside of liver lobules

Kupffer Cells

Cells found along sinusoids in liver lobules. Responsible for removing bacteria from the blood and break down old red blood cells

Deanimation

The process by which nitrogen-containing amino groups are removed from amino acids, forming ammonia and organic acids

Ornithine Cycle

A cycle of biochemical reactions in which ammonia is combined with carbon dioxide to create urea and water

Kidney

Organs in the abdominal cavity that excrete urine.

Ultrafiltration

The filtering of the blood that takes place under high pressure, as blood passes from the glomerulus into the Bowman's capsule

Renal Artery

Blood vessel carrying oxygenated blood to the kidneys

Nephron

One of the filtering units of the kidney, responsible for removing waste substances such as urea from the blood

Loop of Henle

Part of the kidney nephron responsible for establishing the water potential gradient, which allows water to be reabsorbed by the kidney

Countercurrent multiplier hypothesis

A system that expends energy to create a concentration gradient in the medulla of the kidneys.

ADH

Antidiuretic hormone. Responsible for changing the water content of the blood when it's too low or too high by altering the permeability of the DCT and collecting duct in the nephron

Kidney failure

A medical condition where the kidneys are inadequately filtering metabolic waste products, such as urea, from the blood.

Dialysis

The clinical purification of blood by a machine, as a substitute for the normal function of the kidney.

Fixed Monoclonal antibodies

Antibodies used in test strips and pregnancy tests. Often bound to coloured beads, they are highly specific for certain molecules and by changing colour can indicate whether a molecule is present or not

hCG

Human chorionic gonadotropin. A hormone produced by the placenta and present in the urine of pregnant women.

Renal Vein

Blood vessel carrying deoxygenated blood away from the kidneys

Podocyte

Cells in the Bowmn's capsule that wrap around the capillaries in the glomerulus.

Oxidation

Reaction involving the loss of electrons

Reduction

Reaction involving the gain of electrons

Respiration

Release of energy from organic molecules. Energy used to form ATP. Process in all living cells.

Ethanol

Product of anaerobic respiration in plants and fungi

Lactic acid/ lactate

Product of anaerobic respiration in animals

Respiratory quotient (RQ)

Respiratory substrates can be identified by calculating the relationship between the volume of CO2 produced divided by the volume of O2 used.

cytoplasm

Site for glycolysis

Glucose

Most commonly used respiratory substrate

ATP

Universal energy currency in all cells.
Produced in respiration

Glycolysis

First stage of respiration produces pyruvate

Pyruvate

3 carbon molecule produced at the end of glycolysis

NAD

A coenzyme that picks up hydrogen in respiration reactions

Coenzyme A

Picks up the remains of the respiratory substrate after the link reaction and delivers it to the Krebs Cycle

Link reaction

Pyruvate is converted to an acetyl group

Acetyl coenzyme A

Acetyl group 2C and coenzyme A

Krebs cycle

Series of redox reactions in the matrix

Coenzymes

a molecule other than a substrate that an enzyme needs to operate.

Substrate level phosphorylation

A phosphate group is directly transferred from one molecule to another

Oxidative phosphorylation

Energy carried by electrons is used to make ATP from ADP and Pi

Electron transfer chain

A series of proteins embedded in the cristae of the mitochondria

protons

Hydrogen ions

electrons

Sub- atomic particle with a negative charge

matrix

Site of Krebs cycle

cristae

Folds in the inner mitochondrial membrane. Site of electron transport system

Resting Potential

The potential difference across a cell membrane when the cell ( neurone) is at rest

generator potential

The change in potential difference across a cell membrane due to the presence of a stimulus

sensory receptor

A cell, or protein on a cell surface membrane ,that detects a specific stimulus

effector

An organ that becomes active in response to a nerve impulse

transducer

Something that changes one form of energy into another

Electrical potential

A form of potential energy resulting from an unequal distribution of ions across a membrane

voltage -gated channels

Protein Channels ( Sodium and Potassium ) in the axon membrane of neurones that are controlled by voltage ( changes in p.d) . They can open or close.

cholinergic synapse

A synapse ( gap between two neurons) that uses the neurotransmitter substance acetylcholine

all-or-nothing principle

An individual neurone cannot produce action potentials of different magnitudes. If the stimulus does not reach the threshold then there is no impulse.If the stimulus reaches the threshold then the neuron will conduct an impulse

myelination

Neurones with a layer of Schwann cells ( myelin sheath)that act as an electrical insulator

refractory period

Is the span of time during which a second stimulus will be unable to cause an impulse along a neurone.

divergence ( at a synapse)

When one presynaptic neurone connects to many post synaptic neurones

convergence( at a synapse)

Where many presynaptic neurones connect to one post synaptic neurone

depolarisation

A decrease in the potential difference across a cells ( axon) membrane making it less negative ( more positive) than the resting potential.

pacinian corpuscle

A type of mechanoreceptor ( transducer) found in your skin

spatial summation

Term: The convergence of impulses for several different neurons.

temporal summation

occurs when a single presynaptic neuron fires many action potentials in succession, causing the postsynaptic neuron to reach its threshold .

threshold

The level of stimulation required to trigger a neural impulse

dendrites

What part of the nerve cell carries impulses TOWARD the cell?

axon

A threadlike extension of a neuron that carries nerve impulses away from the cell body.

Oxidation

Reaction involving the loss of electrons

Reduction

Reaction involving the gain of electrons

Respiration

Release of energy from organic molecules. Energy used to form ATP. Process in all living cells.

Ethanol

Product of anaerobic respiration in plants and fungi

Lactic acid/ lactate

Product of anaerobic respiration in animals

Respiratory quotient (RQ)

Respiratory substrates can be identified by calculating the relationship between the volume of CO2 produced divided by the volume of O2 used.

cytoplasm

Site for glycolysis

Glucose

Most commonly used respiratory substrate

ATP

Universal energy currency in all cells.
Produced in respiration

Glycolysis

First stage of respiration produces pyruvate

Pyruvate

3 carbon molecule produced at the end of glycolysis

NAD

A coenzyme that picks up hydrogen in respiration reactions

Coenzyme A

Picks up the remains of the respiratory substrate after the link reaction and delivers it to the Krebs Cycle

Link reaction

Pyruvate is converted to an acetyl group

Acetyl coenzyme A

Acetyl group 2C and coenzyme A

Krebs cycle

Series of redox reactions in the matrix

Coenzymes

a molecule other than a substrate that an enzyme needs to operate.

Substrate level phosphorylation

A phosphate group is directly transferred from one molecule to another

Oxidative phosphorylation

Energy carried by electrons is used to make ATP from ADP and Pi

Electron transfer chain

A series of proteins embedded in the cristae of the mitochondria

protons

Hydrogen ions

electrons

Sub- atomic particle with a negative charge

matrix

Site of Krebs cycle

cristae

Folds in the inner mitochondrial membrane. Site of electron transport system

endocrine gland

A gland that secretes its products directly into the bloodstream rather than via a duct

homeostasis

The maintenance of a relatively constant internal conditions

target cells

cells/tissues/organs that contain specific receptor protein in their plasma membranes or in their cytoplasm. These specific receptors are absent on other cells .

islets of Langerhans

Small groups of cells within the pancreas that are responsible for hormone production. Alpha cells which secrete glucagon and Beta cells which secrete insulin.

gluconeogenesis

The synthesis of glucose from molecules that are not carbohydrates,such as amino acids,fatty acids,lactate,pyruvate

glycogenolysis

The breakdown( hydrolysis) of glycogen to glucose. Glucagon activates enzymes which carry out this conversion.

glycogenesis

The conversion ( condensation) of glucose to glycogen. Insulin activates enzymes which carry out this conversion.