Explain the process of aerobic respiration including oxidative phosphorylation [8]

In aerobic respiration, glucose is split into pyruvate by glycolysis. The pyruvate then enters the mitochondria and reacts with coenzyme A by the process of oxidative decarboxylation to form acetyl CoA, in this process carbon dioxide and NADH is formed. The acetyl group then enters the kreb cycle where FAD+ and NAD+ accept hydrogen to form NADH and FADH2. The energy in these molecules is then used to make many more molecules of ATP. In the inner membrane of the mitochondria there are the proteins. Both NADH and FADH2 donate electrons to the electron transport chain. As electrons move from 1 complex to another they transfer their energy to pump protons across the membrane, this then creates a concentration gradient across the membrane. Oxygen is the final electron acceptor; it will then combine with the protons to form water. 

Describe the process of active transport [4]

Active transport is when a protein moves a certain material across the membrane from a region of lower concentration to a region of higher concentration. This means the substance is absorbed against the concentration gradient and energy is needed for this active transport to work. The energy is usually comes from adenosine triphosphate or ATP, every cell supplies its own ATP by cell respiration. Globular proteins or pump proteins or transporter proteins in membranes carry out the active transport, the membrane must contain a lot of these proteins so that the cell can control the contents of its cytoplasm precisely. An example of active transport is in human nerve cells where potassium ions are pumped in and sodium ions are constantly transported out of the cell by active transport into the external fluid bathing the cell to build up a store of potential energy or an electrical impulse that is used to transmit a nerve impulse.

Draw a diagram of the ultrastructure of an animal cell as seen in a electron micro graph [6]

E.2.2 Label a diagram of the structure of the human eye.

E.2.6 Label a diagram of the ear and E.2.7 Explain how sound is perceived by the ear

E.2.4 Compare rod and cone cells.

Photoreceptors are the rods and cones

Both rods and cones synapse with their bipolar neurons

Rod cells are sensitive to light. They receive the stimulus of light, even dim light, and synapse with a bipolar neuron

Cone cells are activated by bright light. They receive the stimulus of bright light and synapse with a bipolar neuron

Bipolar neurons: cells in retina which carry impulses from a rod or cone cell to a ganglion cell of the optic nerve. They are called bipolar because they each have 2 processes extending from the cell body.

Ganglion cells are the cell bodies of the optic nerve. They synapse with the bipolar neurons and send the impulses to the brain.

Rods	Cones
Low/Dim light	Bright light
1 type of rods found in retina. It can absorb all wavelengths of visible light	3 types of cones found in retina. 1 can absorb red light, 1 blue and 1 green
Impulses from a group of rod cells pass a single nerve fibre (Ganglion axon) in the optic nerve	Impulse from a single cone cell passes to a single nerve fibre in the optic nerve

E.2.1 Outline the diversity of stimuli that can be detected by human sensory receptors.

Stimuli are detected by receptors which then trigger sensory neurones to transmit info to the CNS

Different receptors detect different stimuli

Human receptors can be classified as mechanoreceptors, thermo receptors, chemoreceptor’s or photoreceptors

Form of energy detected	Type of receptor	Location in body
Thermoreceptors (heat energy)
Temperature change in the skin	Cutaneous receptors	Dermis of skin
Temperature change in the body	Cells of hypothalamus	Brain
Chemoreceptors (chemical stimulation)
Detects chemicals in the air (smell)	Epithelium of the nasal cavity	Nose
Detects chemicals on the tongue (taste)	Taste buds	Tongue
Detects changes in the composition of arterial blood	Carotid body	Located near the fork of the carotid artery
Osmotic concentration of blood	Osmoreceptor	Kidneys
Mechanoreceptors (movement)
Light Touch	Touch Receptors	Mostly in skin dermis
Touch Pressure	Pressure receptor	Skin
Changes in length of muscle	Stretch receptors such as muscle spindles	Muscle
Sound and balance	Sensory hair cells	Auditory system (ears)
Pressure of blood flowing through vessels	Baroreceptors	Blood vessels
Photoreceptors (light)
Light	Rods and cones	Eye