Biology-2 QWC Practice Questions & Answers

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Biology-2 QWC Practice Questions & Answers

  1. Compare the internal structures of bacterial and yeast cells with those of plants and animals

Bacterial, fungal (yeast), animal and plant cells all have various common features; all have a cell membrane, cytoplasm and a form of genetic material.

 However, in a bacterial cell, this genetic material is presented in an alternative form; unlike the other cells which have their DNA contained inside the nucleus of the cell, a bacterial cell has their DNA found in a `loop` or strands of DNA in the cytoplasm.

Another difference in a bacterial cell, is that they may contain a `whip-like tail` called Flagella so they have the ability to move around, a feature not necessary in the cells of plants, animals and yeast.

A feature that an animal cell does not have, in comparison to the 3 other cell types, is a cell wall, this is because a cell wall ensures that the cell is strengthened and prevents the bursting of the cell, however an animal will not need this feature because they will grow, rather than expand.

What particularly differentiates a Plant cell to the other cells, are that they contain chloroplasts inside them, which enable them to absorb light and subsequently photosynthesize; their form of making food.

To make food for an animal cell, animals simply eat, food for fungal or yeast cells, are stored in a `food storage granule` and a bacteria’s source of food is created through protein synthesis within their ribosomes.

 All the cells apart from a yeast cell contain ribosomes, and only an animal and plant cell contain mitochondria.

  1. Describe, with examples, the process of specialisation in cells.

In animals, cell specialisation occurs at the beginning of their life; embryonic stem cells or `unspecialised cells` differentiate into the cells that make the animals body. However, animals cannot maintain cell differentiation throughout their lives; once a cell is specialised, they cannot become a stem cell once again; the genes for their particular function are switched on, for example, muscle stem cells only have the gene to become muscle cells, the genes for other functions, like becoming nerve cells are `switched off`, and the muscle cell is incapable of becoming any other form of animal cell.

 Stem cells can also be found in adult bone marrow, but these do not produce as many outcomes as an embryonic stem cell would.

On the other hand, in plants, their unspecialised cells maintain the ability to differentiate throughout their lives through meristems, which ensure a plant keeps growing and producing new organs.

  1. Explain what factors can affect the rate of diffusion.

Diffusion is the movement of particles from a higher concentration to a lower concentration, what affects the rate of diffusion includes how large the difference in concentration gradient is, so if there is a higher concentration of a particular particle in one area, and almost no concentration of the same particle in another, the rate of diffusion will be increased. Vice versa, if there was barely any difference in the concentration gradient, the rate of diffusion would be little.

 Another factor affecting the rate of diffusion would be the diffusion distance; the distance necessary to be travelled for diffusion to take place. So if the distance is small, the rate of diffusion will be fast and if the distance is large (assuming the medium is the same), the rate will be slower as there is a need to pass through longer.

 Also, if the diffusion barrier, or what may separate the two sets of particles has a large surface area, diffusion rates will be increased because there are more opportunities to pass through the space, rather than having to pass through a small surfaced `barrier`.

 What can also affect the rate of diffusion can be the state of matter of which is diffused, for example, solids will take longer to diffuse compared to liquids, and liquids will take longer compared to gases. Selecting which medium is used can greatly impact the rate of diffusion.

 Additionally, temperature can impact the rate of diffusion; an increased temperature is likely to result in an increased diffusion. For example, comparing putting squash into water at room temperature and putting squash in boiled water; the squash in the boiled water would diffuse quicker.

 Finally, the nature of the matter itself; the denser the matter, the longer to diffuse. For example, honey will take longer to diffuse compared to ink, because honey is of a denser nature.

  1. Describe the roles of the liver and pancreas in digestion of fats.

In the digestive system, the pancreas produces `digestive juices`, these juices contain enzymes which are biological catalysts, and so speed up the rate of digestion. One of these enzymes includes lipases, which break down fats, or lipids, into fatty acids and glycerol for use around the body.

The liver produces a substance called Bile, which is an alkaline solution in which emulsifies fats, meaning the fats are given a bigger surface area for the enzymes to work on, making it easier for them to catalyse and for our body to digest.

The fact that Bile is alkaline also means that lipase can work at its optimum ph in the small intestine, because it neutralises the food after it has arrived from the acidic conditions of the stomach. Together, the liver and pancreas speed up and provide the correct conditions for digestion.

  1. Describe the adaptations of leaves for photosynthesis

Leaves are adapted both internally and externally for the work of photosynthesis.

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Externally, they provide a large surface area to maximise the sunlight absorbed and are thin to ensure there is a small distance for carbon dioxide to diffuse. Also, there is a thin cuticle of wax on the surface of the leaf to protect it without blocking the essential sunlight.

Internally, the leaf is carefully structured to make sure the plant can photosynthesize as much as possible; found in the upper portion of a leaf, is the upper epidermis which is thin and transparent to allow more light to reach the palisade mesophyll beneath it. The palisade mesophyll contains many chloroplasts ...

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