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prokaryotic cell
single cells and have no membrane-bound nucleus or organelles
bacteria and archaea
prokaryotic
eukaryotic cells
membrane-bound nucleus and membrane-bound organelles
microscope and cells
allowed scientists to see cells for the first time
magnification
how much an image has been increased in size
resolution
minimum distance objects need to be apart to be able to be seen separately
light microscope
pass light rays through thin specimens that are magnified by convex glass lenses, living and non-living specimens can be viewed
magnification and resolution in light microscope
up to 2000×, maximum resolution 200 nm
electron microscopes
transmission electron microscopes (TEM) and scanning
electron microscopes (SEM). No living specimens can be viewed with an electron microscope.
transmission electron microscopes
beams of electrons pass through a specimen and produce a two-dimensional image. Very high magnification and resolution are possible, up to ten million times
scanning electron microscopes
electron beams bounce off surfaces and create a three-dimensional image
organelle
membrane-bound internal structures, each with a specific function to ensure the efficient functioning of the cell
organelle surface area
most organelles have structures that maximise the surface area
organelles observable by light microscope
cell membrane, cell wall, nucleus,
chloroplasts and vacuoles
cell membrane
Selectively permeable boundaries, control the movement of substances into and out of the cell/organelle
nucleus
The control and information centre
smooth endoplasmic reticulum
transports lipids
rough endoplasmic reticulum
transports proteins
golgi apparatus
package and sort proteins
ribosomes
protein synthesis
lysosomes
Digestion and cell destruction
Mitochondria
Cellular respiration – production and storage of energy (ATP)
Vacuoles
Storage and support
Chloroplasts
Photosynthesis
Plant cell wall
Shape and support
cell membrane
selectively permeable barrier and performs the function of controlling the movement of substances into and out of the cell
fluid mosaic model
fluid’ phospholipid bilayer with different types of proteins embedded in it, creating a ‘mosaic’ effect. Proteins either penetrate from one side to the other or are only partially embedded
cell membrane proteins
form pores, some form active carrier systems or channels for transport, and others have carbohydrates attached for cell recognition.
scientific model
used in science for a number of reasons, including to simplify a concept, make a
visual representation of something that can’t be seen, or make predictions of expected results
scientific model validation
Before a model is accepted, it needs to be validated – that is, certain predictions should be made and, when tested using the model, should hold true
cell requirements
Gases, nutrients, water and ions are required by the cell, while wastes and cellular products need to be removed from the cell
permeability of membrane
depends on its size, electrical charge and its lipid solubility.
diffusion
movement of particles from a region of high concentration to a region of low concentration until equilibrium is reached.
equilibrium
no net movement of particles in either direction.
diffusion and energy
does not require the input of energy but occurs faster with a higher temperature or a steeper concentration gradient.
easily diffused molecules
Small, uncharged molecules such as oxygen and carbon dioxide
passive diffusion
allows larger molecules and small electrically charged ions to diffuse across the cell membrane aided by carrier or channel proteins
solution
a solute dissolves in solvent
concentrated solution
has a high concentration of solute and a low concentration of water
osmosis
the process by which water moves from a region of high concentration of water (dilute – low solute) to a region of low concentration of water (concentrated – high solute) which requires no energy input
osmotic pressure
the minimum pressure which needs to be applied to a solution to stop osmosis
Isotonic
fluids inside and outside a cell are of equal solute concentration – no net water movement
Hypertonic
a solution of higher solute concentration (lower water concentration) that surrounds a cell – net movement of water molecules will be out of the cell.
Hypotonic
a solution of lower solute concentration (higher water concentration) that surrounds a cell – net movement of water molecules will be into the cell.
Active transport
the movement of molecules from a region of low concentration to a region of high concentration. moves against the concentration gradient and requires the input of energy
passive transport
the movement of molecules from a region of high concentration to a region of low concentration. moves with the concentration gradient and doesn’t requires the input of energy
Endocytosis
moves large molecules that cannot cross the cell membrane into a cell by creating a vesicle around it. It requires the expenditure of energy
Exocytosis
reverse of endocytosis and used to remove waste
vesicles
small structures in a cell with a lipid layer
surface area to volume ratio
determine how efficiently substances move into and out of a cell.
high surface area to volume ratio
allows the most efficient movement of substances into and out of the cell and is mostly large cells
enzyme
proteins that control cellular reactions
enzyme-catalysed reactions
the substrate attaches to the shape on the surface of the enzyme (the active site) and forms an substrate–enzyme complex
substrate
substance where an enzyme acts on
enzyme models
lock and key model and induced fit model
enzymes and temperature
The activity of an enzyme increases as temperature increases until the optimal temperature is reached. With further temperature increases the enzyme activity decreases and then stops completely when the high temperatures denature the structure of the enzyme
enzymes and ph
Each enzyme has an optimum pH at which it functions most efficiently
enzymes and substrate concentration
As the substrate concentration increases, the activity of the enzyme increases until all the enzymes are saturated. After this, further increases in substrate concentration will not lead to increases in enzyme activity.
energy in cells
transported within cells by small and mobile ATP molecules
atp
stores energy in a high-energy bond that attaches the third phosphate group to the ADP molecule and when energy is required, the high-energy bond is broken, releasing energy, a phosphate group and ADP.