1. Textbook questions
Q1 Active transport requires energy, facilitated diffusion does not (passive process)
Q2 Chloride gets into the cell by diffusion as the concentration outside is higher than inside the cell

2. Learning question: what makes water so special?
Title: Water January 2019
Learning question: what makes water so special?
Homework: Learning package 2 due 23rd September

3. Key words
Polar molecule
Solvent
Plasma
Tissue fluid
Lymph
Serum
Electrolytes

4. Aims from specification
(e) describe the differences between plasma, serum, tissue fluid and lymph;
(f) describe the normal composition of blood plasma;
(g) explain how the properties of water make it an ideal transport medium;
(h) explain the importance of electrolytes in body fluids and outline how they are measured in plasma and urine;

5. Water – a special molecule
Write a short note on why water is a special molecule using all the following key words. You may draw a labelled diagram to illustrate your answer:
Hydrogen bonds
Polar
Small negative charge
Small positive charge
Solvent

6. Water – a special molecule
Water is a polar molecule as it has an uneven distribution of charge. Oxygen atoms have a slightly negative charge, while hydrogen atoms have a slightly positive charge.
Positive hydrogen atoms are attracted to negative oxygen atoms. The forces of attraction that allow water molecules to “stick” together are hydrogen bonds.
Water will surround other polar molecules, such as ions, causing them to dissolve.
Water is a really good solvent as many different chemicals will dissolve in it, e.g salt, sugar and amino acids.

7. Properties of water important to life
Good solvent – transport medium for polar (charged) molecules
Thermostable molecule - less prone to heat damage
Allows cooling for thermoregulation – sweating cools us down
Good support molecule (water molecules “stick” together – are cohesive)
Lubricant properties e.g. mucus and pleural fluid

8. Tissue Fluid
Blood plasma is squeezed out of capillaries as a result of pressure filtration (going from a big artery to a series of smaller ones)
The squeezed out blood plasma is now called tissue fluid
Tissue fluid lacks plasma proteins but contains the rest of the other stuff that was in blood

9. Summary Blood Plasma Tissue Fluid Glucose Amino Acids
Respiratory Gases
Ions
Proteins
 none

10. Exchange Materials
Living cells are constantly bathed in tissue fluid because blood capillaries form a dense network around cells
Tissue fluid is therefore used as a medium to for diffusion of useful and waste substances into and out of the cell

11. Exchange Materials
Useful ions & food

12. Osmotic Return of Tissue Fluid
Majority of tissue fluid returns to the blood vessels at the venule side
This occurs because the tissue fluid lacks plasma proteins and therefore has a higher water concentration – osmosis takes place!
Carbon dioxide and wastes enter the blood by diffusion

13. Lymphatic system Another circulatory system Three main roles: -
drains tissue fluid back
into blood stream
filters lymph
fights infections

14. Lymphatic Return of Tissue Fluid
Some tissue fluid enters the lymphatic system
Once this fluid is lymphatic vessels it is called lymph
Lymph is collected from all parts of the body and returns this fluid to the blood circulatory system
This fluid can only move in one direction because there are valves in larger lymphatic vessels to prevent backflow

16. Lymph and lymph vessels
lymph is mainly tissue fluid collected in lymph vessels
Lymph is moved along by muscular contraction
lymph returns to blood via two lymph ducts

17. Task 2 Complete learning package 4 Q5.
If you complete this, do questions 1 - 4

18. Quiz! Why is water described as a polar molecule?
Give an example of how water is important to life
Explain why fibrinogen and albumin are not present in tissue fluid
Why is water described as a solvent?
How many layers does the plasma membrane have?