Ch 2: Cells Flashcards
What is life?
- Response to the environment
- Exchange of materials with the environment
- Metabolism
- Growth
- Reproduction
Cell is first fundamental sign of life.
Virus is not alive
Prokaryotic cells
- No true nucleus
- 1 to 10 µm
- ex: bacteria
Eukaryotic cells
- Have a true nucleus
- 10 to 100 µm (1/100 to 1/10 mm)
- almost all other cells that are not bacteria
Unicellular
- Each cell carries out all life processes
- Usually found in clusters
- Bacteria are unicellular
Multicellular
Made up of many cells, with different cells specialized to perform different functions
Why are cells so small?
Cells are small because they require a high surface to volume ratio to exchange materials with their environment.
Bacterial cells
- Prokaryotic
- no true nucleus
- no endoplasmic reticulum
- no Golgi apparatus
- no mitochondria
- no chloroplasts
- no vesicles or vacuoles
- no centrosome
Bacterial cell anatomy: Cytosol
- Mixture of enzymes and many other molecules in water.
- Many chemical reactions take place in the cytosol.
Bacterial cell anatomy: Flagellum
- Hair-like
- Attaches at plasma
- Rotates to provide mobility
- Not all bacteria have it
Bacterial cell anatomy: Thylakoid
Provides a membrane for photosynthesis
Not all bacteria have this
Bacterial cell anatomy: Capsule
- Not all bacteria have this
- Thick, sticky, gooey layer
- Protects the cell from attack or dehydration
- Allows some cells to stick together
- When bacteria with a capsule infect you, your immune system doesn’t recognize them/kill them.
Bacterial cell anatomy: Plasmid
- Not all bacterial cells have this
- Accessory genetic information
- Bacteria can trade these
- Scientists can use it to add extra genes for our purposes
Bacterial cell anatomy: Cell wall
- NOT a fluid like the plasma membrane
- Relatively rigid (gives the cell its shape)
- Prevents it from bursting
- Porous
- Most bacteria (not all) have this
Bacterial cell anatomy: Plasma Membrane
- AKA cell membrane
- Boundary between cell and environment.
- Controls movement of material in and out (exchange)
- Made of a phospholipid bilayer
Plasma membrane: Phospholipid bilayer
- Made of lipid molecules that have a polar head and non-polar tails.
- In water, the tails go in towards the center and the heads form two layers surrounding the tails because the heads like water but not the tails (semi-permeable)
- This bilayer is actually a fluid (not solid)
- The non-polar layer makes it relatively non-permeable to polar molecules.
- The non-polar molecules pass through easily (CO2 , O2 , lipids, …). They diffuse through freely.
- Some small polar molecules can actually sneak in, but very slowly.
- Larger polar molecules (ex: glucose) and ions diffuse through hardly at all, but there are some proteins embedded in the bilayer that will let some of the important stuff in.
Facilitated Diffusion (plasma membrane)
- Channel protein: Very specific about what it lets in. No control over in-out direction. Aquaporins (water channels)
- Gated channel proteins: Gates open or close depending on what the cell needs (or other various events)
- Carrier protein: only allows in a specific, but larger molecule.
- All 3 of these help with facilitated diffusion or passive transport (diffusion to areas of smaller concentration)
Active transport protein
- Also for transport in or out of the cell, but not by diffusion (it can bring something in even in concentration is higher inside)
- The cell provides energy to this protein which transports specific molecules in or out of the cell
Animal cells
- no cell wall
- no plasmodesmata
- no chloroplasts
- no central vacuole
- DNA is not in a loop like in prokaryotic cells
Eukaryotic Cell Anatomy (Animal)
Animal Cell Anatomy
Better View of the Cytoskeleton
- Centrosome: Contains centrioles. With pair of centrioles, the centrosome organizes the cytoskeleton
- Cytoskeleton: Gives the cell its shape, allows cell to change its shape, helps with intracellular transport
Eukaryotic Cell Anatomy (Animal)
Plasma Membrane
- Phospholipid bilayer
- Tight junction protein: helps cells stick together
- Extracellular matrix: strengthens tissues, helps cells to react to the environment (with glycoproteins like glycogen)
- Cholesterol: helps maintain membrane fluidity. Non-polar
- Protein receptor: allows cells to respond to only specific chemicals
Eukaryotic Cell Anatomy
Animal
Cytosol
- Synthesis of proteins that need to be packaged
Eukaryotic Cell Anatomy
Animal
Cilium
- Coordinated beating to provide mobility
Eukaryotic Cell Anatomy
Animal
Flagellum
- Unlike in prokaryotic cells, these whip instead of rotate to provide mobility
Eukaryotic Cell Anatomy MITOCHONDRION (Animal)
- Generates ATP for the cell
- Have several features that are similar to a prokaryotic cell
- Outer Membrane: similar to the plasma membrane
- Inner Membrane: similar to a prokaryotic plasma membrane
- Loop of DNA
- Ribosomes: Similar to prokaryotic ribosomes
- Matrix: Fluid, similar to cytosol
Eukaryotic Cell Anatomy
Animal
Nucleus
- Nucleus contains the nucleolus, chromatin and nuclear envelope
- Definining feature of the eukaryotic cell
- Nucleolus: Site of assembly of ribosomes
- Nuclear envelope: Double membrane
- Chromatin: Substance holding most of the genetic information. Made of several diffuse chromosomes (each made of one double-stranded DNA molecule with associated proteins)
Eukaryotic Cell Anatomy
Animal
Smooth endoplasmic reticulum
- Synthesis of lipids
- Destruction of drugs and toxins (we have many in our liver)
Eukaryotic Cell Anatomy
Animal
Rough Endoplasmic Reticulum
- Synthesis of proteins that need to be packaged (i.e. needed in the blood to signal, but not needed in the cell. ex: insulin)
- Looks rough under a microscope because it’s covered in ribosomes
Eukaryotic Cell Anatomy
Animal
Ribosomes
- Protein synthesis
Eukaryotic Cell Anatomy
Animal
Vacuole
- Larger membrane sack of material
- Several types: Lysosome (vacuole of digestive enzymes
Eukaryotic Cell Anatomy
Animal
Vesicle
- Small membrane sack of material
- Small packages that pinched off the rough ER
- Composed of a phospholipid biliayer
- Package will go join the Golgi Apparatus
Eukaryotic Cell Anatomy
Animal
Golgi Apparatus
- Phospholipid bilayer
- Package, modify and sort proteins from Rought E.R.
Plant cells
- no centrosome
- no lysosomes
- cell wall: cellulose. Cell walls are NOT present in animal cells.
- Cytoskeleton, but no centrosome. The nuclear envelope organises part of the cytoskeleton.
- Chloroplasts (site of photosynthesis in plants)
- Large central vacuole (storage, turgor (stiffness caused by water pressure)). Animal cells tend to have many small ones instead.
- Plasmodesmata: channel that allows connection between cells. Allows cytosol and other material to move from cell to cell.
Plant cells: Chloroplast
- Contains a loop of DNA
- Thylakoid: provides a membrane for photosynthesis
- Stroma
- Inner membrane (phospholipid bilayer)
- Outer membrane
- Ribosome
Fungal cells
- eukaryotic
- cell wall: chitin
- pores between cells
- no plasmodesmata
- no centrosome
- no chloroplasts
Cytosis
Transport via folding of a membrane
- Endocytosis: Entering the cell by cytosis
- Exocytosis: Exiting the cell by cytosis
What is different about a Bacterial Cell?
- no true nucleus
- no endoplasmic reticulum
- no golgi apparatus
- no mitochondria
- no chloroplasts
- no vesicles or vacuoles
- (basically no organelles)
- no centrosome
What is different about an Animal Cell?
- No cell walls
- No plasmodesmata
- No chloroplasts
- No central vacuole (only a bunch of little ones)
What is different about plant cells?
- No centrosome
- No lysosomes
- Cell wall is made of cellulose (chemically different than the wall of a bacteria. Cellulose = polusaccharide
What is different about Fungal Cells?
- Eukaryotic
- Cell wall: chitin
- No plasmodesmata
- Pores between cells (large)
- No centrosome
- No chloroplasts
