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

Learning question: what makes water so special? Title: Water 13 January 2019 Learning question: what makes water so special? Homework: Learning package 2 due 23rd September

Key words Polar molecule Solvent Plasma Tissue fluid Lymph Serum Electrolytes

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;

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

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.

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

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

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

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

Exchange Materials Useful ions & food

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

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

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

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

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

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?