How does a cell interact with its environment

1
How does a cell interact with its environment?

• Membrane structure and function
• The cell membrane is a fluid mosaic of lipids,
  proteins, and carbohydrates

2
Why interact with your environment?

• Obtention of food
• Maintenance of homeostasis ? Response to changes
• Regulation of processes

3
The fluid mosaic model
4
Phospholipids

• Major components of the cell membrane
• Amphipathic molecule having both a hydrophobic
  and a hydrophilic region

5

• when added to water, they self-assemble micelle
  and the phospholipid bilayer.
• The phospholipid bilayer forms a semi-permeable
  boundary

6
Membrane response to temperatures

• Fluidity of the membrane

7
Cholesterol

• Its a common component of animal cell membranes
  and functions to help stabilize the membrane
• immobilize the first few hydrocarbon groups of
  the phospholipid molecules. ? lipid bilayer less
  deformable and decreases its permeability to
  small water-soluble molecules.
• Without cholesterol (such as in a bacterium) a
  cell would need a cell wall.
• Cholesterol prevents crystallization of
  hydrocarbons and phase shifts in the membrane.

8
Proteins

• According to localisation
• Periferal proteins
• Integral proteins
• Transmembrane proteins
• Hydrophobic side of the protein in contact with
  the bilayer

9
Integral Proteins

• Association with carbohydrates Glicoproteins
• Cell signaling

10
Cell Junctions

• Animal cells
• tight junctions
• Desmosomes
• Gap junctions.
• Plant cells plasmodesmata
• Each type of junction has specialized functions
• preventing fluid leakage between membranes
• allowing the free passage of small molecules and
  ions between adjacent cells

11
Transport across a membrane

• Passive transport
• Osmosis
• Diffusion
• Facilitated diffusion
• Active transport
• Ion Pumps (ex. Na-K)
• Endocytosis
• Exocytosis

12
Passive transport

• Solute Substance disolved in a solvent

13
Cell response in different concentrations of
solutes
14
Endocytosis and Exocytosis

• Endocytosis is the movement of materials INTO a
  cell via membranous vesicles.
• Exocytosis is the movement of materials OUT of a
  cell
• The membrane is a dynamic, rather than static,
  structure.

15
Types of endocytosis

• Phagocytosis
• Solids
• Pinocytosis
• Fluids
• Receptor- mediated endocytosis

16
Cellular transport

• Look at the illustration of an animal cell. What
  does the illustration represent?
• Why is the animal cell lysed while the plant cell
  is turgid?
• What are the characteristics of an isotonic
  solution?

17
Cellular transport

• One factor that limits cell size is the
  surface-to-volume ratio. Why?
• How do water molecules transport within a cell?
  How is this process called?
• The major lung problems for someone with cystic
  fibrosis are related to which type of transport
  process?

18
Cystic fibrosis

• CF, mucoviscoidosis, or mucoviscidosis
• Hereditary disease affecting the exocrine (mucus)
  glands of the lungs, liver, pancreas, and
  intestines, causing progressive disability due to
  multisystem failure and infections.
• Lung disease results from clogging the airways
  due to mucus buildup and resulting inflammation.