t3 Flashcards
robert hooke and cells
what year?
what did he do?
year : 1665
he built microscopes to examine thin sections of dried cork samples from plants - names cavities cells
cell theory
- all organisms are made up of cells
- the cell is the fundamental unit of life
- cells come from pre-existing cells
prokaryotic cells
prokaryotic cells lack a nucleus and have no internal compartmentalization
eukaryotes cells
eukaryotic cells have a nucleus and internal membrane-bound organelles
hopaniods
-located in membranes of bacteria
- modulate the fluidity of the membrane bilayer
-increase rigidity of the membrane
cholesterol
- found in animal cell membranes
- both polar and non polar regions
- impact membrane fluidity
all cells are defined by a cell man brand (lipids)
- lipids found in the cell membrane are phospholipids
- phospholipids have a hydrophobic tail (non polar region) and hydrophilic head (polar region)
lipid structures micelle
formed by phospholipids with large bulky heads and a single hydrophobic tail
lipid structure bilayer
bilayers and liposomes are formed by phospholipids with small heads and 2 hydrophobic tails
lipid structure phospholipid
when in water phospholipid spontaneously form a liposome, wherein polar heads and non polar tails associate with one another in a bilayer
membranes
membranes are self-healing because they will spontaneously reform
membranes are a fluid mosaic
- lipids and proteins are found in the membrane, forming a mosaic
- pupils are able to move laterally within the membrane
- lipid movement is affected by the nature of the phospholipid tails
saturated vs unsaturated
- van der waals interactions between the fatty acid tails help stabilize the membrane
- bc these interactions are weak, membrane lipids are able to move in the plane of the membrane, thus membrane is fluid
cholesterol
- found in many animal cell membranes
- both polar and non polar regions
- impact membrane fluidity
cholesterol and fluidity
cholesterol acts like a “buffer” for membrane fluidity
proteins in the membranes: transporters and receptors
- transporters that move ions and molecules
- receptors that allow the cell to receive signals from the environment
proteins in the membrane: enzyme and anchors
- enzyme that catalyze chemical reactions in a cell
- anchors that attach to other proteins such as actins or cytoskeleton that help to maintain cell structure and shape
integral proteins
- integral membrane proteins are permanently associated with the membrane and can cross the entire membrane
peripheral proteins
- peripheral membrane proteins are temporarily associated with either side of the membrane
examples of integral membrane proteins
- sodium-potassium pump
- aquaporins
- ATP synthase
examples of peripheral membrane proteins
- cytochrome c
- phospholipase
glycolipid transfer proteins
evidence for the fluid mosaic model: is there movement in the membrane?
- proteins are fluorescently labeled
- one specific region of the membrane is targeted by a laser and photo bleached
- researchers than observe the membrane to see if the bleached area remains, or if fluorescent proteins return to the bleached area
protein ls do move in the membrane
- fluorescence returns to the bleached area, showing that proteins are mobile throughout the membrane
cell membranes
- the cell to the right is a pancreatic cell. the cell is surrounded by a cell membrane which defines the shape and size of the cell
is the cell membrane impermeable?
- all cells are enclosed by a plasma membrane that serves as a boundary defining the space of the cell
- the cell membrane is selectively permeable
selective permeability of cell membranes
- freely permeable: small gas molecules such as oxygen, nitrogen, and co2
- somewhat permeable: small, uncharged polar molecules such as water, ethanol, and glycerol
- impermeable: large, uncharged polar molecules such as glucose and sucrose
- ions such as h+, na, k, cl, etc
simple diffusion: passive transport across the permeable membrane
- movement of molecules from an area of high conc to an area of low conc
- passive transport does not require expenditure of energy from the system
osmosis
-water movement across a permeable membrane (ie. diffusion specific to water)
- movement of water from an area of low solute to high solute
facilitated diffusion (energy not required) ; movement down a concentration gradient through a channel or carrier
- during facilitated diffusion in cells, molecules and substances move from high conc to low conc throughout transporters embedded in the membrane
active transport
- when cells need to move substances against their conc gradient, energy must be expanded
primary active transport
- in primary active transport, the na/k pump uses energy released from hydrolysis of atp to move 3 na ions and 2k ions against the conc gradient
- energy stored in the conc gradient can produce an electrochemical gradient to drive the movement of other molecules through secondary active transport
secondary active transport
- antiporter: h ions return into the cell to exchange for the export other positive ions or molecules such as na
- because the movement of the coupled ions or molecules is driven by the movement of protons and not atp, the transports is called secondary active transports
maintaining cell shape
- cell shape and size in red blood cells change based on the solute conc surrounding the cells
- red blood cells use active transports of ions to keep the internal environment of the cell isotonic to the external environment
maintaining cell shape part 2
- in some single-called organisms, cells contain a contractile vacuole, an organelle
- the contractile vacuole absorbs excess water in the cell and expels it to prevent cell lysis
maintaining cell shape: cell walls
- the cells of many different organisms contain a cell wall, a structure that helps to maintain the cell shape
- the cell wall can be made up of many different compounds but the function of the cell wall is similar in each organism with the structure
cell walls and turgor pressure
- the cell wall provides structural support and protection
- turgor pressure within the cell occurs when water moves into the cell through osmosis
plant cell that animal cell doesn’t have
- cell wall: provides additional support to the cell
- vacuoles: contribute to the structure of the cell by maintaining turgor pressure
- chloroplasts: convert the energy from sunlight into chemical energy that the cell can use
cell organelles: the nuclear envelope
- the nuclear envelope is a double membrane that surrounds the nucleus
- the membrane is perforated by protein openings called nuclear pores, which allow molecules to move into and out of the nucleus
- these pores are essential for the nucleus to communicate with the rest of the cell
