Biology Common Misconceptions

Cell membrane is “partially permeable”. Should avoid using “semi-permeable “

Surface to volume ratio is key to many processes (osmosis, active transport and diffusion) and heat loss is one of them

The key is likened to as the lock, as the substrate is likened to as the key and binds to the active site on the protein enzyme molecules.

The stomach, small or large intestine can reabsorb substance like water that is secreted into the gut as a digestive juice, but not the duodenum, whose wall is thicker and does not absorb significant qualities.

The liver stores glycogen, iron and vitamins.

Liver converts excess glucose into fats and glycogen.

Emulsification does not involve a decrease in the size of fat molecules or fat particles. Bile is not an enzyme and therefore ask others.

Respiration in humans: Energy is released, not produced, during respiration. Energy is needed for respiration but the process releases more energy than energy being used. Higher rate of respiration, the more energy is more than the heat.

It is not correct to say that “oxygen is not breathed in, and carbon dioxide is breathed out”. Exhaled air contain urea.

In describe the mechanism of breathing

Increase in volume of thoracic cavity   -à         drop in pressure in lungs   –à             pressure inside becomes lower than the atmospheric pressure outside    à   pressure different forces air into lungs [not that air rushes or moves into lungs on its own.]

Transport in humans: The lack of nucleus in red blood cells increases the volume available for oxygen carrying molecules, not to hold extra oxygen molecules.

Poor interpretation of graphed pressure changes during cardiac cycle.

The role of vitamins, minerals, enzymes and prothrombin in blood clotting are beyond the required syllabus knowledge

Confusion between antigens and antibodies

Plant nutrient and transport: For substances to be translocated, they need to be in solution, hence starch cannot be translocated.

A plant wilts because more water is lost through transpiration than absorbed.

In a wilted plant, the stomata may close, but will open as carbon dioxide accumulates. The water potential of the cells will be lower [more negative]

Because of the loss of water.

In high temperature, stomata closes

Transpiration is defined as the loss of water vapour from the leaves, not just the loss of water from plants. Water also can be lost from plants by guttation. Water in the plant cells push against the cellulose cell walls and creates turgor pressure. Surrounding cells push against each other creating support for the plant.

Coordination and control:

While a person is perspiring, it is water that evaporates, not sweat.

Respiration is a source of heat energy.

Blood temperature, not body temperature is monitored by the hypothalamus in the brain.

The coordination of temperature regulation is carried out by the brain.

The balance of hormone production is what helps maintain blood glucose concentration within narrow limits.

Function of suspensory ligaments transmit force from the ciliary muscle; are structures that attach the lens to the ciliary body.

Common misconceptions:

-Ciliary body relaxes [instead of ciliary muscle]

-Suspensory ligaments relaxing [instead of ciliary muscle]

-Lens becoming taut [instead of suspensory ligaments]

Sexual Reproduction in Plants: Asexual reproduction is not the same as self- fertilisation.

Sexual reproduction in humans: Advantage of sexual reproduction is that generic recombination leads to variety, not simply that it helps off springs to become better adapted.

Fertile period in most women normally last from about 11 to 19.

Egg and sperm fuses together in the fallopian tube, for more likely than in the uterus.

A zygote divides to form the embryo, not the other way around.

The large size of the ovum is related to the fact that it needs to store the initial nutrients for the development of the embryo, and the release of only one ovum at a time is related to the limited space available for the subsequent development of the embryo.

Molecular genetics: Difficulty in describing relationship between genes and chromosomes.

The order of bases in DNA molecules is what forms the code for the formation of proteins.

Cell division: Misconceptions

-Mitosis occurs in all cells.

-The parent cell in meiosis is haploid.

-Meiosis involves fusion of cells.

Man and the environment: Both carbon dioxide and oxygen MUST be recycled to maintain life.

Micro-organisms in sewage treatment include aerobic and anaerobic bacteria and fungi.