Cells & internal environment

Question 1

What makes up the body fluid?

Answer 1

• 18% protein
• 15% fat
• 7% minerals
• 60% water

Question 2

How does females body water content compare to males?

Answer 2

They have slightly less than males
Women have 50% compared to men who have 60%

Question 3

What happens to your body water content with age?

Answer 3

It decreases
Causes wrinkles?

Question 4

What are the 3 compartments that water is stored in the body and the %?

Answer 4

• Blood plasma –> 5%
• Interstitial fluid –> 15%
• Intracellular fluid –> 40%

Question 5

What is intracellular fluid?

Answer 5

In cells - makes up 40% of the 60% water content

Question 6

What is interstitial fluid?

Answer 6

Between cell and bloodstream (15%)

Question 7

What is blood plasma fluid?

Answer 7

fluid found in blood vessels

Question 8

What is blood plasma?

Answer 8

The fluid in the bloodstream

Question 9

What maintains the balance of water between the cells and capillaries?

Answer 9

Osmotic equilibrium maintains the constant % in each of the 3 compartments

Question 10

Where can we gain and lose water from?

Answer 10

The lungs/kidneys - can be lost by vomiting, respiration or urinating

Question 11

What makes up a cell membrane?

Answer 11

A phospholipid bilayer (Fluid-mosaic model)

Question 12

What makes up a phospholipid?

Answer 12

A phosphate head and 2 fatty acid chains

Question 13

What are the properties of the phosphate head?

Answer 13

It is hydrophilic (likes H2O) so draws to the water, forming the outside of the membrane

Question 14

What are the properties of the fatty acid chains in a phospholipid?

Answer 14

Hydrophobic (doesn’t like H2O) so pulls the membrane together in the middle

Question 15

How do phospholipids organise themselves?

Answer 15

Into spheres to form a membrane due to the behaviours of the tails and head

Question 16

What are the conc. of ions around the cell?

Answer 16

• Na+ & Ca- ions are more conc outside the cell
• K+ ions more conc in cell
• Proteins much higher conc in cell

Question 17

What are the factors that determine the permeability of the membrane?

Answer 17

• Size of molecule
• Lipid solubility
• Charge (ionisation)

Question 18

How does size affect the permeability of a molecule?

Answer 18

Smaller molecules pass through membrane easier

Above 3nm = less passage

Question 19

How does lipid solubility affect the permeability of a molecule?

Answer 19

More lipid soluble means more permeable - due to the phospholipids

Question 20

Which molecules pass through membranes easily?

Answer 20

O2 and N2

Small & no charge

Question 21

Which molecules find it hard to pass through membranes without aid?

Answer 21

Sugars, amino acids, peptides etc

They require transport proteins

Question 22

What are the main ways that substances are moved across membranes?

Answer 22

• Diffusion
• Filtration
• Osmosis
• Protein mediated transport (two types)
• Active transport

Question 23

What are the two types of protein mediated transport through membranes?

Answer 23

Carrier proteins and channel proteins

Question 24

What is involved in diffusion?

Answer 24

• From high to low conc. (down conc grad)
• Small soluble molecules pass through membrane
• Collisions that cause random movements
• Net movement from high –> low (movement happens in both directions)
• Can happen in open system or across partition

Question 25

What is involved in filtration?

Answer 25

- Takes place in kidneys - Filtration barriers - most substances can pass through, not all - Plasma delivers substances - proteins cannot pass through as too large - Stops the body losing important proteins

Question 26

What is involved in osmosis?

Answer 26

- Movement of water across membrane in response to a solute concentration grad - Low to high - Osmotic pressure (P) - Moves across semipermeable membrane - Helps cell shrink/swell

Question 27

What is osmotic pressure (P)?

Answer 27

Pressure which would prevent H2O moving

Question 28

What is involved in protein mediated transport?

Answer 28

- Proteins act as carriers & channels - Facilitate flow of substances that cannot permeate lipid bilayer - High to low conc. using facilitated diffusion down the conc gradient

Question 29

What is protein mediated transport used for?

Answer 29

Helps ions & large unionised molecules pass across a bilayer

Question 30

What do carrier proteins do?

Answer 30

The protein combines w substrate, transports it across & releases it into the cell Are generally specific to the substrate

Question 31

Give an example of the use of a carrier protein

Answer 31

RBCs taking up glucose via GLUT1 transporters

Question 32

What do channel proteins do?

Answer 32

They permit movement through the cell membrane (through a channel) - via osmosis e.g. Na+ aquaporins

Question 33

What happens in active transport?

Answer 33

Move molecules against the conc gradient - Uses ATP to produce energy for movement ATP --> ADP using ATPase to release energy

Question 34

What is endocytosis?

Answer 34

The movement of substances into cells Traps protein in membrane to move through

Question 35

What is exocytosis?

Answer 35

Movement of substances out of cells Uses vesicles which fuses w cell membrane --> calcium dependent e.g. hormones & NTs