Cells & internal environment Flashcards
What makes up the body fluid?
- 18% protein
- 15% fat
- 7% minerals
- 60% water
How does females body water content compare to males?
They have slightly less than males
Women have 50% compared to men who have 60%
What happens to your body water content with age?
It decreases
Causes wrinkles?
What are the 3 compartments that water is stored in the body and the %?
- Blood plasma –> 5%
- Interstitial fluid –> 15%
- Intracellular fluid –> 40%
What is intracellular fluid?
In cells - makes up 40% of the 60% water content
What is interstitial fluid?
Between cell and bloodstream (15%)
What is blood plasma fluid?
fluid found in blood vessels
What is blood plasma?
The fluid in the bloodstream
What maintains the balance of water between the cells and capillaries?
Osmotic equilibrium maintains the constant % in each of the 3 compartments
Where can we gain and lose water from?
The lungs/kidneys - can be lost by vomiting, respiration or urinating
What makes up a cell membrane?
A phospholipid bilayer (Fluid-mosaic model)
What makes up a phospholipid?
A phosphate head and 2 fatty acid chains
What are the properties of the phosphate head?
It is hydrophilic (likes H2O) so draws to the water, forming the outside of the membrane
What are the properties of the fatty acid chains in a phospholipid?
Hydrophobic (doesn’t like H2O) so pulls the membrane together in the middle
How do phospholipids organise themselves?
Into spheres to form a membrane due to the behaviours of the tails and head
What are the conc. of ions around the cell?
- Na+ & Ca- ions are more conc outside the cell
- K+ ions more conc in cell
- Proteins much higher conc in cell
What are the factors that determine the permeability of the membrane?
- Size of molecule
- Lipid solubility
- Charge (ionisation)
How does size affect the permeability of a molecule?
Smaller molecules pass through membrane easier
Above 3nm = less passage
How does lipid solubility affect the permeability of a molecule?
More lipid soluble means more permeable - due to the phospholipids
Which molecules pass through membranes easily?
O2 and N2
Small & no charge
Which molecules find it hard to pass through membranes without aid?
Sugars, amino acids, peptides etc
They require transport proteins
What are the main ways that substances are moved across membranes?
- Diffusion
- Filtration
- Osmosis
- Protein mediated transport (two types)
- Active transport
What are the two types of protein mediated transport through membranes?
Carrier proteins and channel proteins
What is involved in diffusion?
- 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
What is involved in filtration?
- 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
What is involved in osmosis?
- 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
What is osmotic pressure (P)?
Pressure which would prevent H2O moving
What is involved in protein mediated transport?
- 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
What is protein mediated transport used for?
Helps ions & large unionised molecules pass across a bilayer
What do carrier proteins do?
The protein combines w substrate, transports it across & releases it into the cell
Are generally specific to the substrate
Give an example of the use of a carrier protein
RBCs taking up glucose via GLUT1 transporters
What do channel proteins do?
They permit movement through the cell membrane (through a channel) - via osmosis
e.g. Na+ aquaporins
What happens in active transport?
Move molecules against the conc gradient
- Uses ATP to produce energy for movement
ATP –> ADP using ATPase to release energy
What is endocytosis?
The movement of substances into cells
Traps protein in membrane to move through
What is exocytosis?
Movement of substances out of cells
Uses vesicles which fuses w cell membrane –> calcium dependent
e.g. hormones & NTs
