• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Exchange with the environment.

Extracts from this document...


Exchange with the environment Definitions * Heterotrophic Organisms: These obtain their carbon in the form of ready-made complex organic substances, such as glucose. * Catabolism: This is the process of the breakdown of complex substances into simpler ones, such as the breakdown of glucose to carbon dioxide and water, in the process of cell respiration. * Autotrophic Organisms: These can make complex organic compounds from simple inorganic substances, such as carbon dioxide and water. Exchange processes * Living organisms constantly need to exchange materials with the environment in order to survive and grow. * Organisms need to respire to release energy from their food. * Most organisms take up oxygen from the environment and, as a consequence of the catabolic reaction involved, release carbon dioxide as a waste product. * Heterotrophic organisms require a ready-made source of food, which they obtain from their environment. This food consists of complex organic compounds, which need to be digested into simple, soluble molecules. Any undigested material is egested and thus returned to the environment. * Autotrophic organisms make their own organic nutrients from simple, inorganic molecules. To achieve this, they need to obtain the raw materials from their environment. * Green plants are photoautotrophs, which mean they use light energy in the process of photosynthesis. ...read more.


It is also present in many glands, where it has a secretory function. Squamous epithelium consists of thin, flattened cells with little cytoplasm. The nucleus of each cell is disc-shaped and centrally situated. Cytoplasmic connections exist between adjacent cells. The cells fit closely together and, when viewed from above, the margins of the cells are seen to be irregular (tesselated). This type of epithelium is found in the Bowman's capsule of the kidney, the alveoli of the lungs and lining the blood vessels and the chambers of the heart. Columnar epithelium is made up of tall, narrow cells. A large spherical nucleus is situated near the base of each cell and the free surface often possesses microvilli. Mucus-secreting goblet cells are often found amongst the columnar cells. This tissue lines the stomach and intestine, and is also present in some ducts of the kidney. Respiratory gas exchange As has already been mentioned, aerobic respiration is common to most living organisms and necessitates the uptake of oxygen and the release of carbon dioxide. Respiring cells are constantly using up oxygen and releasing carbon dioxide, so concentration gradients exist between the organism and its environment with respect to these gases. Usually within the organism there will be a lower concentration of oxygen and a higher concentration of carbon dioxide than in the environment, so oxygen tends to diffuse in and carbon dioxide diffuse out. ...read more.


In such cases, the oxygen-carrying capacity of the blood is increased by the presence of a respiratory pigment. In mammals, this pigment is haemoglobin and is present in specialised blood cells: erythrocytes. * The respiratory surface needs to be permeable to the respiratory gases. All cell surface membranes are permeable to oxygen, carbon dioxide and water. Gas exchange in flowering plants Gas exchange in the flowering plants involves the aerial parts, mainly the leave and stems. Leaves have a large surface area: volume ratio, which is favourable for the exchange of gases. Access to the respiring cells is by means of Stomata, which are pores in the epidermis of the leaves. Inside the leaf, the large intercellular air space in the spongy mesophyll facilitate the diffusion of gases and cells bordering these air spaces increase the total area available for gas exchange still further. During the day, when photosynthesis is occurring, the fixation of carbon dioxide maintains a concentration gradient of carbon dioxide between the interior of the leaf and the external atmosphere. The rate of diffusion of carbon dioxide is directly proportional to the concentration gradient, but it is also affected by factors such as the number and size of the stomata, the cuticle of the leaf and the layer of air surrounding the leaf. As these are factors which also affect the movement of water in the plant. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Energy, Respiration & the Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Energy, Respiration & the Environment essays

  1. Marked by a teacher

    Effect of nitrate concentration on the growth of Duckweeds

    5 star(s)

    So the solutions containing 0%- 0.4% x 10-3 nitrate concentration had a higher water potential than the fluid inside the cells cytoplasm. Therefore this caused water from the solution to move inside the root cells of the duckweeds, and prevent dehydration.

  2. Marked by a teacher

    The Role of the Respiratory and Circulatory Systems in the Provision of Oxygen and ...

    3 star(s)

    Air then passes the cartilage flap called the epiglottis, which is present to stop food entering the trachea. The larynx, which is responsible for producing vocal sounds, opens into the pharynx at the entrance of the trachea. The trachea then connects the pharynx to the lungs.

  1. the effect of bile concentration on the activity of the enzyme lipase during the ...

    increase as the chances of successful collisions become greater therefore the bile salts have a direct effect on lipase's activity as they increase the surface area. Therefore the rate at which the pH drops will increase as lipase breaks the fat molecules into glycerol and fatty acid lowering the pH.

  2. Investigate the effect of bile salt concentration on the digestion of milk by the ...

    bile salts were the value for the rate of reaction is too low compared to the other rates of reactions at 3% and 5%. A table to show the different statistical techniques I used Bile Salt Concentration 0% 1% 2% 3% 4% 5% Lower value -1.1 0.1 0.4 0.3 0.2

  1. Ecology of leaves

    Which are considerably more and therefore the plant will loose the excess water by increasing surface area, which will cause there to be more stomata on the leaves surface area. Another reason for the significant differences between the light exposed area and the light shaded area, maybe due to photosynthesis.

  2. Why the Body Needs Energy? Every living cell within the ...

    and (anteriorly). It works as part of both the digestive and respiratory system The Structure of the Pharynx * The pharynx is about 12.5cm long and is made of muscular and fibrous tissues. * At the back of the section of the pharynx which connects to the nose are small

  1. the Effect of Copper Ions on a

    Volume of inhibitor, enzyme and amylase- 2cm3 of CuSO4, 4cm3 of 0.2% bacterial amylase and 4cm3 of 0.1M starch solution will be placed in each test tube resulting in a total volume of 10cm3 in each test tube. Preliminary Method 1.

  2. The Homeostatic Mechanisms

    Also, when the body?s temperature increases, thermo receptors cause the hypothalamus to activate the sympathetic nervous system, which causes the heart to beat faster. The heart rate increases under pressure e.g. when a person is feeling stressed or has done exercise.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work