Photosynthesis - Absorption spectrum.

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Biology Notes

Photosynthesis

                          light

Water + carbon dioxide → glucose + oxygen

6H2O + 6CO2 → C6H12O6 + 6O2

Absorption Spectrum

An absorption spectrum shows which wavelength of light a molecule absorbs.

Action Spectrum

An action spectrum shows the effect of each wavelength of light on the rate of photosynthesis

The absorption spectrum of chlorophyll is very similar to the action spectrum of photosynthesis. This is evidence that chlorophyll absorbs light for photosynthesis.

The Light and Dark Reaction

1) The light reaction

         light

6H2O→12H + 3O2                Light splits water into hydrogen ions and oxygen.

2) The dark reaction

               enzymes

12H + 6CO2 → C6H12O6 + 3O2        Glucose is then formed from the hydrogen ions and carbon dioxide. (This reaction does not occur in the dark).

Factors affecting the rate of photosynthesis

The Light Reaction

Chlorophyll can split more water molecules at higher light intensities. Photosynthesis will reach a maximum rate when chlorophyll is saturated by sunlight.

The Dark Reaction

An increase in temperature will increase the rate of glucose production until it reaches the optimum temperature for the enzymes.

The enzymes will be denatured if it goes above a certain temperature.

An increase in carbon dioxide will also increase the rate of glucose production.

Millions of years ago there was much more carbon dioxide in the atmosphere, the plants sucked up the carbon dioxide and pumped out oxygen, this gave the atmosphere we have today.

These factors depend on each other. They must all be at their optimal amount for photosynthesis to occur at a maximum rate. The factor that restricts the effect of the others is known as the ‘limiting factor’.

Use of glucose from photosynthesis

Respiration

Energy is released from glucose and used for growth and repair.

Storage

Glucose is stored as starch. Starch is insoluble and so doesn’t change the osmotic potential of the cell. Starch is made of long chains of glucose molecules. It can be broken down when glucose is needed.

Transport

Glucose is turned into sucrose for transport in the phloem around the plant.

Synthesis of other substances

Chains of glucose molecules form cellulose for cell walls. Glucose + nitrates and sulphates from proteins. Glucose + phosphate forms DNA. Glucose + magnesium forms chlorophyll.

Mineral Nutrition in Plants

Plants need water, carbon dioxide and light. They also need many minerals:

  • Nitrates – nitrogen is needed for proteins, leaf and stem growth
  • Phosphates – phosphorous is needed for respiration, photosynthesis, healthy roots and DNA
  • Potassium – needed for leaf and flower growth
  • Magnesium – needed for chlorophyll

The plants absorb water and dissolved minerals through the roots. The water and the dissolved minerals are transported in the xylem to the stem and leaves. This is called the transpiration stream.

Mineral Deficiency Symptoms

  • Nitrogen deficiency – weak stem, stunted growth, yellow leaves. This is because due to no sunlight being trapped since there’s no chlorophyll.
  • Phosphate deficiency – stunted growth, poor root growth, purple leaves. This is because of poor root growth so less photosynthesis because of less water and minerals being sucked up.
  • Potassium deficiency – yellow leaves, poor fruit and flower growth. Since it has yellow leaves, this means there’s no chlorophyll to trap sunlight so less photosynthesis takes place.
  • Magnesium deficiency – yellow leaves, stunted growth. Same as above.

Digestion

Definition

Digestion is the breakdown of large, insoluble food molecules into small, soluble molecules so that they can be absorbed into the bloodstream.

Effect of temperature on Enzymes

Boiling the liver denatured the catalyst. This means that the catalyse does not work. This happens because the linkages in its molecules break down this is due to the high temperature. As the temperature goes up, so does the rate of reaction for the enzyme, but once it has gone past its optimum temperature the rate of reaction drops rapidly, and the enzyme will become denatured.

Teeth and Feeding

  • Enamel – covers the exposed part of the tooth and makes a hard biting surface.
  • Dentine – it is like bone, and it is softer than the enamel, calcium helps to strengthen it.
  • Pulp – this is the centre of the tooth, it is a soft connective tissue, it contains cells, which make the dentine and keep the tooth alive.
  • Cement – it is a bone like substance, which covers the roof of the tooth.
  • Incisors – used to cut pieces off the food
  • Canines – used similarly to incisors
  • Premolars – used to crush food to small pieces
  • Molars – same as premolars

Adaptation of teeth and skull to diet

Diets

Carnivore

Protein rich meals, long intervals between meals, teeth used to catch prey as well as physical digestion.

Herbivore

Food is poor in nutrients, large quantities of food eaten frequently, mostly cellulose that is difficult to digest, food is ‘harvested’ and not caught.

Carnivores

Incisors – Theses are pointed, and is able to apply more pressure, which means it is easier to cut off food, the incisors in the bottom jaw are like a more chiselled shape, and is there to pierce. Incisors are there to meet and grip the prey and to tear flesh away from near the bone.

Canines – The canines are long, curved and very sharp, they are there to hold and kill the prey. They can exert a lot of pressure to pierce the skin; also can be used as weapons when fighting for a mate.

Per/molars – The 1st molar on the lower jaw and the last premolar on the upper jaw are called the carnassials teeth. These teeth slide past each other like scissors, they pass and cut flesh and crack bones. They shear flesh from the prey. The other teeth are flattened and have sharp edges for cutting flesh and cracking bones.

A Carnivore’s teeth are adapted very well since they only eat flesh, which means they eat other animals. The incisors are there to cut the flesh off the animal and to keep the prey from moving too much. The canines are there to grip and kill the prey, these are adapted very well, and since they are sharp so it can pierce the prey’s skin very easily. The molars and premolars are there to crush bones and chew the flesh even further; these are very well adapted since the top teeth would fit nicely into the bottom ones, making the chewing processes a lot of efficient. Carnassials teeth are adapted very well, since they fit together like scissors, they can crush bones and cut off pieces of flesh a lot easier.

The joint between the lower and upper jaws are close fitting allowing only up and down movement. This also makes it hard to dislocate when struggling with prey. Large temporal muscle provides force to cut flesh and break bones. The temporal muscle is attached to the ridge on the top of the skull. Eyes are set in the skull facing forward; this is so they can judge the distance between them and their prey, so they can decide when to pounce. Carnivores have a very small masseter muscle since they do not use it very often. Carnivores also have a thick skull; this is to protect itself when catching prey or when fighting for mates.

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Herbivores:

Incisors and canines – there are only incisors and canines in the lower jaw; these teeth are used to cut through plants. They are similar in size and shape. Lower teeth act as blades cutting upwards against the horny pad (cropping).

Pre/molars – these teeth slide other each other and grind the food. They have a broad surface for grinding. The upper teeth have a W shape, and the bottom teeth have an M shape, so they fit together nicely, and can grind the food more efficiently. Enamel has worn away in the troughs leaving hard enamel ridges. But ...

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