Posts Tagged ‘protein’

Option H – Hormonal control

Friday, March 2nd, 2012

As we delve into Option H, we’ll be reviewing human biology concepts at the same time.  This first section is about hormonal control.  Hormones are chemical messengers secreted by endocrine glands into the blood and transported to specific target cells.  They can be steroids (eg progesterone, testosterone, estrogen), proteins (eg insulin, ADH, FSH, LH) and tyrosine derivatives (eg thyroxin).

You need to:-

  • Distinguish between the mode of action of steroid and protein hormones.
  • Outline the relationship between the hypothalamus and the pituitary gland.
  • Explain the control of ADH (vasopressin) secretion by negative feedback.

Another fantastic presentation here.  We’ll use this one too. Hormonal Control

Energy in human diets

Friday, January 15th, 2010
fine crop of rice by shop boy on flickr

fine crop of rice by shop boy on flickr

Did you know that per 100g, carbohydrates and proteins contain similar amounts of energy whereas fats contain more than double that?  Actual figures are: 1760 kJ for carbohydrates, 1720 kJ for protein and 4000 kJ for fats (per 100g).

Differences exist between various ethnic groups in terms of their main dietary source of energy.  Your task will be to research different ethnic groups that use rice, wheat, cassava, maize, fish and meat as their staple energy source, and to compare their diets.

 

MSG by PunkJr on flickr

MSG by PunkJr on flickr

In addition, we will consider that there are social issues relating to inappropriate diets, especially in the developed world.  There is also highly effective marketing of unhealthy foods by profit-making companies (I saw a TV ad recently espousing the benefits of MSG!).  With this in mind, you must be able to explain the possible health consequences of diets rich in carbohydrates, fats and proteins. [Consequences of an excess of each type of nutrient should be explained separately.]

What makes us stop eating?  We have an appetite control centre in the brain.  Do some research and find out how it works.

Cell membrane structure

Monday, November 16th, 2009
Simple diffusion in cell membrane from wikimedia commons

Simple diffusion in cell membrane from wikimedia commons

Some questions to tackle this week:-

  • Do you know what a phospholipid is? 
  • Can you draw a labelled diagram of a cell membrane?
  • What other structures are present in the membrane to help it perform its function of allowing substances into and out of cells?
  • How does this relate to diffusion?
  • Can you explain why the membrane is described as fluid?

Here are some links to images and animations that might help you understand the answers to these questions.

Simple diagram of cell membrane.  More complex diagram of cell membrane.

Animation showing that the cell membrane is selectively permeable by only allowing molecules that are small enough to pass across.

This animation shows how protein channels can help diffusion of larger molecules across the membrane.

This interactive animation explains diffusion and how it relates to membrane structure.