Unit 2
Cells
Characteristics of LIving things
Made of cells
Respond to stimuli
Adapt to the environment
Growth and reproduction
Use energy
Maintain homeostasis
Cell theory
All living things are made of cells.
Cells are the basic unit of structure and function of living things.
All cells come from other cells.
Types of Cells
Prokaryote
1st cells
Evolved first on the Earth
Very simple
Lack most organelles
Example: Bacteria
Eukaryote
Evolved from prokaryotes
Complex
True nucleus
Have various organelles
Example: plant, animal, fungus and protists
Prokaryote Bacteria
Cell Wall: Made of peptidoglycan: uses for support (difference between a Gram + and Gram -
Cell Membrane: Regulates what enters and leaves the cell (homeostasis)
Ribosomes: Site of protein synthesis
(no membrane), Different size than eukaryotes
Nucleoid: Region of the cell that the DNA is located
Plasmids: small circular piece of DNA that bacteria can exchange
Pili: Connect to other Bacteria to exchange plasmids
Flagella: Long tail that aids in movement.
Organelles
Cell Wall
All cells except Animals
Protects and supports the cell
Made out of carbohydrates
Cell Membrane
All cells
Regulates what goes into and out of the cell
Cytoplasm
All cells
Liquid part of the cell (Mostly water)
Cytoskeleton: protein network that holds the organelles in place
Nucleus
All Cells except bacteria
Contains the DNA and nucleolus
Nucleolus
All Cells except bacteria
found in the nucleus and makes ribosomes
Ribosome
ALL CELLS
Not membrane bound
Site where proteins are made
Main function of the cell is to make proteins
Endoplasmic Reticulum
All cells except bacteria
allows for the transport within the cell
Smooth = no ribosomes
Rough = ribosomes
Golgi Apparatus
All cells except bacteria
site where proteins are modified prior to use
Chloroplast
Only in plant and algal cells
site of photosynthesis
Mitochondria
Found in all cells except bacteria
Site where the the energy of glucose is converted into ATP
Lysosome
All cells except Bacteria
Contain enzymes to allow for the digestion of molecules within the cell
Vacuole
All cells except bacteria
Very large in plant cells
Storage sacs for water, salts and minerals
Centrosomes
Found in animal cells
Make spindle fibers to use in cell division
Cell Membrane
Cell Membrane
Made of Biomolecules
Carbohydrates
Lipids
Proteins
Selectively permeable - only certain material is able to pass
All cells contain a cell membrane
All organelles except ribosomes contain a membrane
Lipids
Phospholipids
Main body of the cell membrane
Hydrophilic Head
Contains a Phosphate
LIkes water
Polar
Hydrophobic Tail
Made of 2 fatty acids
Doesn’t like water
Non-polar
Bilayer
The fatty acid tails point towards each other
Phosphate heads are outwards by the watery fluids
Only small nonpolar molecules can easily cross between the fatty tails
Cholesterol
Fits in between the phospholipids
Holds the phospholipids together without making it too stiff
Prevents membrane from freezing
Proteins
Large molecules that are embedded throughout the membrane
Many different types
Channel Proteins: move large or polar molecules across the membrane
These will be open from one side of the membrane to the other
Carrier proteins: binds to material and moves them through a channel protein
Acts like a key to open the channel protein to move the material across
Carbohydrates
Glycolipids
Glycoproteins
Function
Cell communication
Tells neighboring cells that it needs something
Tells neighboring cells that it is going to divide
Cell recognition
How cells know that cell belongs to you
How cells know that cell belongs to an organ
Your body can recognize non-self cells and mark them for death
What factors influence how molecules move across the cell membrane?
Size
Small can fit through the phospholipids
Large go through a protein
Polarity (charge)
Nonpolar = phospholipid
Polar = protein
Shape
Proteins work like a lock and key
Concentration
The greater the concentration difference, the faster diffusion will occur
Types of Transport
Passive Transport
Movement of molecules from an area of high concentration to an area of low concentration
With the concentration gradient
Across the membrane
Until it reaches equilibrium
All the molecules are equally spaced
Molecules continuously move
No energy is required to move across the membrane
Examples
Diffusion
Movement of molecules/material through phospholipids
HIgh concentration to low concentration
Reach equilibrium
No energy required
Facilitated diffusion
Diffusion with assistance from a membrane protein
Still from high to low concentration
No energy required
Example
Glucose
Na+
Osmosis
Facilitated diffusion of water only
Water moves toward solutes
Reach equilibrium
No energy
Really water moves in response to solute concentration
Solute is the stuff dissolved into the water
Water wants to dilute the solute, so it moves to the higher solute concentration
Example situation
Hyperosmotic
Means more solute on the outside of the cell
Water move out of the cell
Cell shrinks
Also known as plasmolysis
Hypoosmotic
Means less solute outside of the cell
More solute inside of the cell
Water moves in
Cell will expand
Also known as Turgor Pressure
Helps plants to stand tall
Isosmotic
Equal amount of solute in and out of the cell
Equal movement of water in and out of the cell
No net loss or gain to cell size
Active transport
Molecules move against the concentration gradient
Low concentration to High concentration
Never reach equilibrium-actively working AGAINST equilibrium
Requires a protein
Requires energy
Examples:
Sodium-potassium pump = used in nerve function and muscle cell contractions
Electron Transport Chain = used in photosynthesis and Cell Respiration
Endocytosis = bring materials into a cell
Exocytosis = removal of material from the cell