Download Cell Boundaries

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

List of types of proteins wikipedia, lookup

Mitosis wikipedia, lookup

Cytokinesis wikipedia, lookup

Extracellular matrix wikipedia, lookup

Amitosis wikipedia, lookup

Organ-on-a-chip wikipedia, lookup

Endomembrane system wikipedia, lookup

JADE1 wikipedia, lookup

Cellular differentiation wikipedia, lookup

Cell culture wikipedia, lookup

Cell growth wikipedia, lookup

Cell encapsulation wikipedia, lookup

Cell cycle wikipedia, lookup

Tissue engineering wikipedia, lookup

Signal transduction wikipedia, lookup

Cytosol wikipedia, lookup

Cell membrane wikipedia, lookup

Cell wall wikipedia, lookup

Cytoplasmic streaming wikipedia, lookup

Programmed cell death wikipedia, lookup

Biochemical switches in the cell cycle wikipedia, lookup

Cell Boundaries
The roles of the cell membrane and
the cell wall….it’s all about transport
(active and passive)
Structures that enclose the cell
• Cell membrane is the outer boundary of
every cell
• Role is to separate and protect the cell from
its surroundings
• Cell membrane is selectively permeable
• Phospholipids and the lipid bilayer
• Role of proteins and carbohydrates
In plants: the cell wall
• Cell wall located outside the cell membrane
and serves to support and protect the cell
• Found in PLANTS ONLY
• Cell walls are very porous; allow water,
gases to pass through easily
• Primarily cellulose (carbohydrate) and some
It’s about Transport
• Cell membranes help the cell regulate its
internal chemistry
• Cells maintain a constant internal
environment by compensating for
environmental changes.
• This is called homeostasis
• Use a combination of Passive Transport and
Active transport
Passive Transport
• Substances cross the cell membrane without
the cell expending energy
• Process is diffusion: this is how substances
spread through a liquid or a gas
• Substances move from regions of high
concentration to regions of lower
Passive transport (diffusion)
• Small molecules like alcohol, water and
small lipids diffuse directly across the cell
• Cell membranes have hundreds of different
kinds of protein channels to allow diffusion
of specific molecules (like glucose)
• This use of channels is called facilitated
Special case: diffusion of water
• Diffusion of water across the cell membrane
is called OSMOSIS
• Like all other substances water diffuses
form regions of high concentration to
regions of low concentration
• Pure water has a higher concentration of
water than a solution does
• This has important consequences for a cell
The consequence: Osmotic
• Movement of water causes powerful
pressure; high enough to burst the cell
• Cells deal with this:
– By having cell walls (physical strength)
– Pumping out water (special structures)
– By having blood to bathe the cells (blood and
cells have same concentrations of dissolved
Active Transport
• Movement of substance against a
concentration gradient
• ALWAYS requires energy; can be compared
to a pump
• Used to transport large molecules into the
cell, pareticles of food and sometimes
whole other cells
Active Transport
• Endocytosis: the cells engulfs large
particles and takes the particle into the cell
• Endocytosis is also called phagocytosis
– Protozoans
– White blood cells
• Exocytosis: cells use energy to expel
particles from the cell