BIOLOGY UNIT 4

DESCRIBE THE STRUCTURE OF CHLOROPLAST IN RELATION TO PHOTOSYNTHESIS. (LIGHT DEPENDENT AND LIGHT INDEPENDENT REACTIONS)

Thylakoid Membranes are the site of light dependent reactions. As they contain photosystems, electron carrier proteins. Thylakoid space provides space for accumulation of Hydrogen ions. Grana are joined together by lamella which maintain proper distance between grand to maximise light absorption. The chloroplast also contains chlorophyll which traps light from the sunlight. System of membrane disc known as thylakoid stack us grana, existing as layers to increases surface area for light absorption.

The Storm is the site of light independent reaction, As it contains enzymes such as RUBISCO that are involved in the calvin cycle.

Describe how global warming may be caused.

Greenhouse gases such as carbon dioxide, water vapour and methane from deforestation and burning of fossil fuels, accumulate in the atmosphere. U.V light pass through greenhouse gases while infrared radiation from the sun that has been absorbed and radiated by the surface of the earth is absorbed and reradiated back to the surface of the earth by the greenhouse gases in the atmosphere, thus increasing the temperature at the surface of the earth.

How is HIV able to enter the cells.

the viral gp120 (on HIV) is complementary to CD4 receptors on the surface membrane of T helper lymphocyte. The virus envelope fuses with the cell surface membrane of the T helper cell. HIV can also enter into macrophage via phagocytosis.

Infection of HIV

The Gp120 on virus is complemntary with the CD4 receptors on the surface membrane of lymphocytes or T helper cell. The viral RNA enters the lymphocyte and produces viral DNA by reverse transcriptase. Viral DNA becomes part of host cell DNA by integrate. Viral proteins are synthesised and form new viruses, lymphocytes are destroyed when new viruses bud out of the cell. T killer cells also destroy heavily infected T helper cells / lymphocytes .

T helper cells produce cytokines to activate b cells and t killer cells and this lowers immunity to other diseases and death is caused by opportunistic disease like TB or pneumonia

barriers to entry: skin and skin flora

The skin is strengthened by keratin, which makes it impermeable. antimicrobial secretions by the skin like oil and sebum inhibits microbial growth

skin flora: a bacteria that prevent growth of pathogenic bacteria, by competing for space and nutrients and release substances that inhibit their growth.

How does Decomposition take place?

Bacteria and fungi act as decomposers, they feed on dead bodies and faeces and break them down by secreting extracellular enzymes such as proteases,carbohydrase, cellulase that hydrolyse bonds and release simple molecules. The decomposers then respire these simple molecules and release carbon dioxide and NH3 (if respiring proteins) into the atmosphere. The rest of the simpler molecules are returned to the soil.

Methods of prevention and control

have stricter hygiene practices - handwashing for doctors, nurses and visitors. wear sterile clothing and changing clothes and bedding everyday. isolation of patients . allowing fewer visitors in and out

controlling the use of antibiotics

use antibiotics when strictly needed and dont use antibiotics ti treat viral diseases or to prevent one.

complete the antibiotic course

take prescribed dose of antibiotic

use narrow-spectrum antibiotics to avoid killing natural flora

there should be a rotation in the use of antibiotics

use a few different antibiotics and intrude new ones when available.