Transcript Macromolecules & the Cell Membrane

Macromolecules, the Cell
Membrane, and Movement
Sections 7.3 and 2.3
Organic Macromolecules
• Organic matter has carbon in it, but it has a
few exceptions including carbon dioxide,
carbon monoxide, etc. Living things are made
up of carbon and other elements.
• 4 Categories of Organic Macromolecules
– Carbohydrates, Nucleic Acids, Proteins, and Lipids
Carbohydrates
• Carbohydrates are sugars made of
carbon, hydrogen, and oxygen.
• They are used as an energy source
and can be either
monosaccharides or
polysaccharides
– Monosaccharides: single chain
sugars; used quickly; EXAMPLE:
glucose
– Polysaccharides: multi-chain sugars;
put into storage; EXAMPLE:
glycogen
Nucleic Acids
• Nucleic Acids are made up of
nucleotides
– Nucleotides have a sugar,
phosphate, and a base
• They transmit genetic
information in the form of
DNA and RNA
– DNA: deoxyribonucleic acid
– RNA: ribonucleic acid
Proteins
• Proteins are made up of
amino acids.
– Structural proteins provide
shape and structure for a
physical trait. EXAMPLE: hair
– Enzymes are specialized
proteins that bind to
activation sites and speed up
a chemical reaction. LIVING
THINGS NEED ENZYMES TO
CARRY OUT THE FUNCTIONS
OF LIFE!!!
Lipids
• Lipids are fats and oils.
• Lipids have a hydrophilic
( “water”“loves” ) head
and a hydrophobic
(“water” “fear”) tail
• LIPIDS MAKE UP
MEMBRANES IN CELLS!!!
Cell / Plasma Membrane
• Composed of double layer of phospholipids and
proteins
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
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Phospholipids
• Heads contain glycerol & phosphate
and are hydrophilic (attract water)
• Tails are made of fatty acids and are
hydrophobic (repel water)
• Make up a bilayer where tails point
inward toward each other
• Can move laterally to allow small
molecules (O2, CO2, & H2O to enter)
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The Cell Membrane is Fluid
Molecules in cell membranes are constantly
moving and changing
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Cell Membrane Proteins
• Proteins help move large
molecules or aid in cell
recognition
• Peripheral proteins are
attached on the surface
(inner or outer)
• Integral proteins are
embedded completely
through the membrane
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GLYCOPROTEINS
Recognize
“self”
Glycoproteins have carbohydrate tails to act as markers for cell recognition
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Cell Membrane in Plants
Cell membrane
• Lies immediately
against the cell wall
in plant cells
• Pushes out against
the cell wall to
maintain cell shape
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Diffusion
• Solutions have solutes dissolved in solvents (e.g. salt
dissolved in water). The ratio between the solute and
the solvent is the concentration.
• Usually molecules move from a HIGHER concentration
gradient to a LOWER one through diffusion. For
example, this is why you are able to smell freshly bakes
cookies after they have started to cook.
• When diffusion occurs, molecules move so that they
are equally spread out in a space. This is called
equilibrium.
Diffusion
Osmosis
• Osmosis is the diffusion of water. Cells need water, so
this is especially important in Biology.
• Water is attracted to the solute and moves towards it
because it is going from a HIGHER concentration of
water to a LOWER concentration.
– Isotonic: solution outside of the cell is EQUALLY
concentrated; water moves in and out but there is no net
change
– Hypertonic: solution outside of the cell is MORE
concentrated; water leaves cell
– Hypotonic: solution outside of the cell is LESS
concentrated; water enters the cell
Osmosis
Facilitated Diffusion
• Sometimes molecules that are moving from a
higher concentration to a lower concentration
cannot pass through a cell membrane because
they are too large.
• Facilitated diffusion occurs when special
proteins in the cell membrane serve as a VIP
doorway for these large molecules.
Facilitated Diffusion
Active Transport
• When molecules move AGAINST the
concentration gradient, this is called active
transport
• Molecules can either be pumped across the
membrane using a specialized protein pump or
be escorted by parts of the membrane that break
off and surround the material.
– Endocytosis: when the membrane surrounds a
molecule to go INTO the cell
– Exocytosis: when the membrane surrounds a
molecule to go OUT of the cell
Active Transport – Protein Pump
Active Transport - Endocytosis
Active Transport - Exocytosis