Biology

• Prokaryotic Cells

  • single-celled organisms.
  • simplest living things on the planet
  • single chromosome
  • have a cell wall
  • ends attach so that it forms a circle
  • don't have a nucleus
  • don't have any special compartments
  • e.g. Bacteria and Archaea
• Eukaryotic Cells

  • unicellular and stand-alone
  • have a plasma membrane to hold all their contents inside.
  • more complex than prokaryotic cells
  • have organelles
  • have nucleus
  • DNA is housed
  • have straight-line chromosomes since they have a protective nucleus
  • e.g. yeast, animals, plants, and fungi
• organelles


  individual compartments
• nucleus

  • large organelle in a cell
  • sac that holds the DNA genome.
  • DNA replication and transcription
• cell membrane

  • barrier separating the cell from the outside world.
  • made from 2 layers of phospholipids that create a nonpolar hydrophobic region in the middle
• membrane

  • help anchor things, direct things, and invite things in.
• Cytoplasm

  • Prokaryotes and Eukaryotes
  • liquid goo that fills out the inside of the cells
  • mostly water, but contains ions and proteins
  • things travels in and out of the cell and travelling between organelles
• cytoskeleton

  • prokaryotes and eukaryotes
  • skeleton type structure for the cell

  
  

  * microtubules - built and broken down as needed to move things like organelles and chromosomes around the cell

  * microfilaments - built and broken down as needed to help cells move and stretch, esp. muscle cells

  * intermediate filaments: form the basic scaffold to hold up the cell
• nucleolus

  • eukaryotes
  • ribosomes are made
• nucleus

  • eukaryotes
  • DNA is kept
  • DNA replication and transcription
  • surrounded by two membranes
• mitochondria

  • eukaryotes
  • cell creates energy in the form of ATP
  • Krebs cycle and electron transport chain occur here

  * matrix - inside part
• endoplasmic reticulum

  • Eukaryotes
  • folded membranes that winds its way through the cell like a series of canals
  • The space between the membranes is similar to the environment outside of a cell, and the cell uses it as a staging area for things that will eventually get sent out.

  Types:

  * Rough

  • covered with ribosomes
  • make proteins requiring special treatment

  *Smooth

  • not covered with ribosomes
  • makes lipids and breaks down drugs and alcohol
• Ribosomes

  • Prokaryotes and Eukaryotes
  • translation occurs (mRNA to proteins)
  • can be found in the cytoplasm or on the rough ER
• Golgi Apparatus

  • eukaryotes
  • a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion.
  • In addition, as noted earlier, glycolipids and sphingomyelin are synthesized within the Golgi.
• Lysosomes

  • Eukaryotes
  • enzyme tanks where the cell sends things it wants eliminated
• vacuoles

  • eukaryotes
  • a membrane-bound cell organelle.
  • In animal cells, vacuoles are generally small and help sequester waste products.
  • In plant cells, vacuoles help maintain water balance.
• Cell wall

  • prokaryotes, plants, and fungi
  • plants and fungi have a cell wall like prokaryotic cells because this gives them a bit more stability
• chloroplast

  • plants only
  • found in plants and green algae
  • extract energy from sunlight so they can make sugar
• central vacuole

  • plants only
  • Plant cells have a huge vacuole filled with a watery fluid
  • The plant vacuole is almost like a second cytoskeleton and gives support to the plant
  • dry plants- low on fluid
• Flagellate

  • this movement requires flagella

  *Flagella

  • microscopic hair-like structures involved in the locomotion of a cell.
  • made from microtubules
  • type of building block used in the cytoskeleton
  • e.g. bacteria and other unicellular organisms, human sperms
• Ciliate

  • this movement depends on the presence of many tiny hairs called cilia

  *Cilia

  • made from microtubules
  • very small but have a large number
  • brush back and forth and create a wind/wave effect
  • sometimes an entire cell can be covered in cilia
  • cilia brush back and forth, they push waves of water or food into the mouth structure
  • move dust and particles out of the lungs. It is a constant tiny upward breeze out of the lungs

  paramecium: type of protest that uses cilia to eat
• Amoeboid

  • type of movement named for amoebas
  • does not require any fancy whips
  • ONLY requires the cytoskeleton to stretch or reach in a direction so much that the cell membrane bulges out
  • slow process
  • helps amoebas to move toward food and also to surround food and engulf it
  • in the body, immune cells move around by slowly stretching and sliding to search for invaders

  Pseudopod

  • extending bulge of the cellular membrane
  • "false foot"
  • formed: the cell anchors it and then the rest of the cell shifts to follow along
• Diffusion

  • spreads out until everything is even
  • movement of something from where it is the most concentrated to the area where it is least concentrated

  
  

  Concentration Gradient: when things are not equally spread out

  
  

  Lots of something = high concentration

  few of something = low concentration

  going from high to low concentration is moving DOWN the concentration gradient

  going from low to high is moving AGAINST/UP the concentration gradient
• Osmosis

  • diffusion of water

  * water goes from where there is lots of water to where there is little water

  * that water dilutes other things like the sugary inside of a cell or the salty ocean

  Solute- dissolved in water (or another liquid)

  Solvent- the liquid

  Hypertonic- more dissolved particles

  Isotonic- same amount of dissolved particles

  Hypotonic- fewer dissolved particles
• Passive Transport

  • natural movement of things across the cell membrane.
  • no energy required to move
  • the movement is because of diffusion
  • Types: simple diffusion and facilitated diffusion
  • things will cross the membrane until there are equal levels on each side of the membrane
• Simple Diffusion

  • simple hydrophobic things can zip across the membrane
  • oxygen and carbon dioxide can do this
  • Nonpolar
• Facilitated Diffusion

  • special tunnels/channels so they can get through without touching the hydrophobic space
  • polar things like water can't pass through the membrane
  • only allow certain things to get through
  • great when things want to diffuse
• Active Transport

  • requires energy to force something to move in a direction that is against natural diffusion
  • accomplished using ATP
• Primary Active Transport


  using the energy from ATP for transport
• Secondary Active Transport


  ATP is indirectly used to move something.

  • uses ATP indirectly because it uses a gradient set up by primary active transport to move a second substance
• endocytosis

  • uptake of things
  • the membranes begin to pinch together at the surface. This causes the pocket to become an enclosed circle and then the original membrane reattaches
• exocytosis

  • does the reverse of endocytosis
  • small vesicles arrive at the surface of the cell and slowly start to wiggle their membranes into the cell membrane
• Fission

  • bacteria reproduce by binary fissions

  Binary fission: process of making clones of themselves

  First they copy their ingredients, including their circular chromosome.Then, the cell grows. Finally, the membrane sort of pinches togetherin the middle and the cell wall pinches together until there are twocells where there once was one.
• FISSION PROCESS

  Fission process

  A) Cell elongates and DNA is replicated

  B) Cell wall and plasma membrane begin to divide

  C) cross wall forms completely around divided DNA

  D) cells separate

  E) cell wall

  F) plasma membrane

  G) DNA (nuclear area)

  
• Cell division 


  ongoing process for multicellular organisms

  • cells die and other cells take their place
• mitosis


  process of cell division
• our skin cells and intestinal cells have a particularly high turnover rate. Brain cells don't divide very much
• Interphase

  • cells are not dividing
  • Three phases: G1, S, and G2
  • S phase- Synthesis (DNA Replication occurs)
  • genome is divided into chromosomes, & each chromosome must be copied during DNA replication
  • there is a lag time before mitosis starts, the body keeps the original and the new copy of a chromosome attached
• sister chromatids

  • held together at the chromosome's centromere
  • while the chromosomes are attached they're called sister chromatids