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7.3: CELL TRANSPORT (across the cell membrane!)
Vocabulary
• Osmosis• Diffusion• Facilitated Diffusion• Osmotic Pressure• Isotonic• Hypertonic• Hypotonic
• Active Transport• Endocytosis• Exocytosis• Protein Pumps
Background Info…• Every living cell contains a liquid interior
(cytoplasm) and is surrounded by a liquid.
• The cell (plasma) membrane separates what is inside the cell from what is outside of the cell
• What is the MAJOR function of cell membrane?– regulate the movement of molecules from one side of
the membrane to the other.• In other words—control what gets in and what gets out!
Selectively permeable: • property of biological membranes which
allows some substances to pass more easily than others
Transport proteins: • membrane proteins that transport
SPECIFIC molecules or ions across biological membranes
GLUCOSE
Binding
TransportRecovery
Dissociation
Movement across the cell membrane can
be: 1) PASSIVE cell does not have to spend
energy substance moves from where it
is MORE concentrated to where it is LESS concentrated.
2) ACTIVE cell “spends” energy to move a
substance from where it is LESS concentrated to where it is MORE concentrated (“UPHILL”)
Passive Transport: DIFFUSION
• movement of a substance from where it is conc. to where it is less conc. (“down a concentration gradient”)
Passive Transport: OSMOSIS
• diffusion of WATER
across a selectively
permeable membrane;
water moves DOWN its
concentration gradient
INSIDE THE CELL
OUTSIDE THE CELL
– the direction of water movement water can be described/predicted based on if the cell’s environment is:
• ISOTONIC: equal solute concentration compared to inside a cell
• HYPERTONIC: greater solute concentration than inside a cell
• HYPOTONIC: lower solute concentration compared to inside a cell
WATER MOVES FROM HYPO TO HYPERTONIC!!!
In animal cells: • in a HYPERTONIC environment,
water exits the cell;
cells shrivel and usually die
• in a HYPOTONIC environment,
water moves into cell,
causing it to swell and
possibly burst
In cells with cell walls (i.e. plant cells): • in a HYPERTONIC environment, water exits
the cell; cells shrivel and usually die
• in a HYPOTONIC environment, water moves into cell, causing it to swell; cells become more TURGID.
Passive Transport: FACILITATED DIFFUSION
• diffusion of solutes across a membrane, with the help of transport proteins
(passive transport because it is movement down a concentration gradient; cell does not need to spend any energy)
ACTIVE TRANSPORT: energy-requiring process; molecules are moved across the cell membrane AGAINST their concentration gradient (“uphill”)
ACTIVE TRANSPORT: ENDOCYTOSIS & EXOCYTOSIS
• transport of large molecules (e.g. proteins and polysaccharides) into or out of the cell
ENDOCYTOSIS EXOCYTOSIS
*importing large molecules by forming vesicles out of the cell membrane**vesicle forms in a small region of cell membrane***used by cells to bring in larger, extracellular substances (e.g. proteins)
ENDOCYTOSIS EXOCYTOSIS
*exporting large molecules by vesicles fusing w / the cell membrane**vesicle buds from ER or Golgi and migrates to cell membrane***used by cells to export products (e.g. cells in pancreas secreting insulin)
2 types of Endocytosis:
1) Phagocytosis: solid particles (“cell
eating”)
2) Pinocytosis: fluid droplets (“cell
drinking”)
Phagocytosis
Pinocytosis
What are the 3 types of passive What are the 3 types of passive transport across a membrane?transport across a membrane?
a)a) Diffusion, osmosis, and exocytosisDiffusion, osmosis, and exocytosis
b)b) Exocytosis, endocytosis, and Exocytosis, endocytosis, and phagocytosisphagocytosis
c)c) Diffusion, facilitated diffusion, and Diffusion, facilitated diffusion, and osmosisosmosis
d)d) Diffusion, osmosis, and endocytosisDiffusion, osmosis, and endocytosis