COMMUNICATION, HOMEOSTASIS AND ENERGY

BIOLOGY NOTES

MODULE 5

snaprevise.co.uk

DISCLAIMER

The information presented is no way produced or endorsed by any exam board.

A-LEVEL REVISION & EXAM PREP IN A SNAP

Concise & exam board specific videos

Visit snaprevise.co.uk to find out more

High quality notesand summaries

Created by A* students

I have designed and compiled these beautiful notes to provide a detailed but concise summary of this module. I have spent a lot of time perfecting the content as well as the presentation to make your learning as easy as possible and less daunting.

3

INDEXTOPIC 1: COMMUNICATION AND HOMEOSTASIS . . . . . . . . . . . 6

1. The Need for Communication Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Cell Signalling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Homeostasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Ectotherms and Endotherms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

TOPIC 2: EXCRETION AS AN EXAMPLE OF HOMEOSTATIC CONTROL . . 12 1. The Importance of Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. The Mammalian Liver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3. The Kidney . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4. The Control of Blood’s Water Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5. Kidney Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6. The Use of Excretory Products in Medical Diagnosis . . . . . . . . . . . . . . . . . . . . . 22

TOPIC 3: NEURONAL COMMUNICATION . . . . . . . . . . . . . . 24 1. Sensory Receptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2. Sensory, Relay and Motor Neurones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3. Nerve Impulse Generation & Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4. Synapses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

TOPIC 4: HORMONAL COMMUNICATION . . . . . . . . . . . . . . 31 1. Endocrine Communication by Hormones . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2. The Adrenal Glands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3. The Pancreas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4. Regulation of Blood Glucose Concentration . . . . . . . . . . . . . . . . . . . . . . . . . . 34 5. Diabetes Mellitus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

TOPIC 5: PLANT AND ANIMAL RESPONSES . . . . . . . . . . . . . 38 1. Plant Responses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2. Plant Hormones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3. Experimental Evidence for The Role of Auxins . . . . . . . . . . . . . . . . . . . . . . . . . 41 4. The experimental evidence for the role of gibberellin . . . . . . . . . . . . . . . . . . . . 41 5. The Commercial use of Plant Hormones . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 6. The Mammalian Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 7. The Human Brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 8. Reflexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 9. Nervous and Endocrine Coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4

10. Regulation of Heart Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 11. The Neuromuscular Junction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 12. Mammalian Muscle and Muscular Contraction . . . . . . . . . . . . . . . . . . . . . . . . 52

TOPIC 6: PHOTOSYNTHESIS . . . . . . . . . . . . . . . . . . . . . . 58 1. Photosynthesis and Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 2. Chloroplasts and Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3. Factors Affecting the Rate of Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . 62

TOPIC 7: RESPIRATION . . . . . . . . . . . . . . . . . . . . . . . . . 65 1. The Need for Cellular Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 2. The Mitochondrion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3. Glycolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4. The Link Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5. The Krebs Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 6. Anaerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 7. The Difference in Respiratory Substrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 8. The Respiratory Quotient (RQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 9. Practical investigations into factors affecting the rate of respiration . . . . . . . . . . . . 71

TOPIC 1

Communication and

Homeostasis

6snaprevise.co.uk

Communication and Homeostasis

1 The Need for Communication Systems

Keeping Cells Active

• All organisms needs to maintain a limited set of conditions • Need to respond to changes in external and internal environments • This is because cellular activities rely on enzymes which require a specific set of conditions to work effectively

• Organs need to coordinate their activity to maintain optimal internal conditions that support survival

2 Cell Signalling

When cells communicate by signalling, one cell releases a chemical

• This chemical is detected by another cell • The second cell then responds to this signal

There are 2 major systems of communication:

Neuronal System

• Network of neurons • Quick signals • Rapid responses

Hormonal System

• Uses blood to transport signals • Endocrine organs secrete hormones directly into blood • Carried all over the body • Only recognized by specific target cells • Enables long-term responses to be coordinated • Specific target cells have receptors that have a shape that is complementary to the shape of the hormone

7snaprevise.co.uk

3 HomeostasisHomeostasis is the regulation of internal environments independently of external environments

These include: • Temperature • Blood glucose concentration • Blood salt concentration • Water content • Blood pressure • Blood carbon dioxide partial pressure (blood pH)

Negative Feedback

• Reversal of a change in the environment to return to the optimum position • Receptor detects the change • Communication systems inform the effectors • The effector reacts to reverse the change • Eg: maintaining blood pressure • Pathway:

Positive Feedback

• Response causes change to increase • Destabilizes the system • Usually more harmful • Does not lead to homeostasis • Can be useful in certain situation • Eg: childbirth - uterine contractions • Pathway:

View more for FREE

snaprevise.co.uk

These notes are intentionally incomplete, to view more click the

button above.