BIOLOGY IGCSE CIE EXAM Q

STRUCTURE OF ARTERY, VEIN, AND CAPILLARY

Artery: Thick muscular wall, high pressure, narrow lumen

Vein: Thin wall, valves to prevent back flow, wide lumen, low pressure

Capillary: Single layer of cells, facilitates exchange of materials

HOW DOES THE BODY MAINTAIN INTERNAL TEMPERATURE

Body maintains internal body temperature through homeostasis (1) Thermo-receptors detect change in external temperature and sends nerve impulse to the brain (2) If it gets cold, there will be vasoconstriction and shivering (3) If it gets hot, vasodilation and sweating (4)

DEFINITION OF TISSUE AND ORGAN

Tissue: Group of cells working together to perform/carry out one function

Organ: Group of tissues working together to perform/carry out one function

HOW IS BLOOD GLUCOSE CONCENTRATION CONTROLLED?

If an increased concentration of glucose is detected in the blood, the pancreas detects it and begins secreting insulin to convert glucose and store it as glycogen in the liver. If the blood glucose level is too low, the pancreas detects it and sends a signal to the liver to release the store glycogen and convert it to glucose via. the hormone glucagon, which is secreted by the pancreas. This is an example of negative feed back in homeostasis.

PROCESS OF ULTRAFILTRATION IN THE NEPHRON

Substances in the blood such as water, ions, glucose, urea, and amino acids are filtered into the Glomerulus to pass through the semi-permeable membrane into the Bowman's capsule. This process selectively allows substances to pass while retaining larger molecules like proteins and blood cells. All glucose is reabsorbed. Only some water, ions and amino acids are reabsorbed. Urea, water, and ions then pass into the convoluted tube and collecting duct and form urine. This is transported to the ureter.

IMPORTANCE OF PROTEINS IN ACTIVE TRANSPORT

Protein carriers move the substances such as ions across a membrane during active transport against the concentration gradient.

THE PROCESS OF BLOOD CLOTTING

Platelets gather at the site of the wound, releasing a chemical which converts soluble fibrinogen to insoluble fibrin which forms a mesh layer at the area, trapping blood cells and clotting the wound. This prevents pathogens from entering the bloodstream and any future infections.

HOW DOES CHOLERA CAUSE DEHYDRATION

1) Cholera pathogen produces a toxin

2) This toxin secretes chloride ions

3) Travels into the small intestine

4) Loss of ions increase water potential

5) Causing water to leave the cells into the intestinal lumen via. osmosis

6) This results in diarrhoea and dehydration

THE PROCESS OF VACCINATION

1) Weakened version of the virus is introduced to the body

2) Antigens stimulate an immune response

3) Lymphocytes create antibodies

4) Antibodies bind to antigens and defeat the virus

5) Memory cells are formed

6) Referred to as active and long term immunity

HOW ARE IMPULSES PASSED DOWN

Neurotransmitters are released from their vesicles from the pre-synaptic neurone, travelling down and diffusing across the synaptic gap to bind with complementary receptors on the post-synaptic neurone, transmitting electrical signals, which carry impulses.

DISTRIBUTION OF RODS AND CONES IN THE EYE

Rods and cones are found in the retina, with a higher concentration of cones in the fovea. There are no rods or cones in the blindspot of the eye. Rods detect low light intensity, which gives night vision and produces a greyscale image. Cones detect high light intensity, allowing for the eyes to detect colour.

THE PROCESS OF DEAMINATION

The removal of nitrogen containing parts of amino acids to form urea.

WHAT ARE SOURCES AND SINKS

Sources: Part of the plant that releases sucrose and amino acids

Sinks: Stores and uses sucrose and amino acids

During the summer, where lots of sunlight is available, the leaves are the source as they can make sugars with photosynthesis and the roots are the sink to store.

During the winter, the roots act as sources and release stored sugars but leaves do not use the source from the roots to grow.

THE PROCESS OF VOLUNTARY ACTION

1) Stimulus

2) Receptor neurone

3) Sensory neurone

4) CNS

5) Motor neurone

6) Effector

7) Response

THE TRANSPORTATION OF BLOOD IN THE HEART

1) Deoxygenated blood enters the vena cava into the right atrium

2) Right atrium contracts and pumps blood to the right ventricle through the tricuspid valve

3) Right ventricle contracts and pumps blood through semi-lunar valve which closes to prevent back flow out to the lungs through pulmonary artery for gas exchange

4) Oxygenated blood enters heart through pulmonary vein into the left atrium

5) Left atrium contracts and pumps blood through bicuspid valve and into the left ventricle

6) Left ventricle contracts and pumps blood through the semi-lunar valve, out the aorta to the entire body

WHAT HAPPENS DURING INSPIRATION

1) Ribs move upwards and outwards

2) Diaphragm contracts and flattens

3) Lungs expand

4) Lung volume increases

5) Lung pressure decreases

THE PROCESS OF PROTEIN SYNTHESIS

1) mRNA is synthesised from gene in DNA in the nucleus

2) DNA stays inside nucleus

3) mRNA travels to cytoplasm

4) mRNA attaches to ribosome

5) Ribosome translates the mRNA sequence to assemble a chain of amino acids, forming proteins

!! It is important to remember that the base sequence of DNA determines the sequence of mRNA that is translated into proteins.

THE PROCESS OF GENETIC ENGINEERING

1) Plasmid is cut via. restriction enzyme

2) Gene is cut from DNA using ligase

3) Gene inserted into plasmid

4) Plasmid vector is used to insert gene X into required cell and will multiply many times.