biology unit 1 aos 1

the purpose of cell division

• repair (replace damaged and existing cells)

• growth (allow for growth and differentiation of cells)

• reproduction (the production of new organisms)

the cell cycle

• events that take place from one cell division to another

interphase

• the stage between divisions where chromosomes aren't visible, cells spend most of there time there and do its assigned job

G1 phase

the cell produces new proteins, organelles duplicate,

S phase

• DNA replication occurs so that each chromosome is made up of two chromosomes

G2 phase

• the cells grow again and prepares for cell division

M phase

• mitosis

prophase

• chromosomes thicken and shorten to prepare for division, become visible, nuclear membrane disintegrates

metaphase

• chromosomes meet in the middle, become attached to spindle fibres

anaphase

• chromosomes are pulled apart by spindle fibres to opposite sides of the cell

telophase

• chromosomes uncoil

• spindle fibres disintegrate

• nuclear membrane forms around the two nuclei

cytokinesis

• after mitosis to separate the cells the outer membrane divides resulting in two separate cells

cytokinesis in plant cells

• a new cell wall must form around each daughter cell, a cell plate is formed prior to the cytoplasmic division

cytokinesis in animal cells

• a ring of actin fibres forms at the metaphase plate, the ring contracts forming a cleavage furrow that divides the cell into two

apoptosis

• programmed cell death

purpose of apoptosis

• is essential for development, shaping organs and tissues and removing cells that are old or infected

• cells with DNA damage can pose as a threat, if they do to the rest of the organism, it is removed

• will try to repair itself, if unsuccessful it is sent to apoptosis

the difference between the 2 ways of apoptosis

• trigger is either external (DR) or internal (M), starts at the cell membrane (DR) of mitochondria (M)

the general process of apoptosis

• 1) cells with damage receive a signal to apoptosis (either pathway)

• 2) caspases are activated to break down the cell, cytochrome c from the mitochondria is released which activates more caspases, the membrane begins to bleb

• 3) the cell shrinks and the membrane continues blebbing due to caspases breaking down cellular components

• 4) the membrane continues blebbing

• 5) apoptotic bodies form

phagocytosis (apoptosis)

• a macrophage that engulfs apoptotic bodies, not actually a part of apoptosis

binary fission

• cell division in prokaryotic cells

difference between mitosis and binary fission

• less complex in prokaryotic cells compared to eukaryotic

• allows bacteria to replicate much faster

• bacteria are the fastest reproducing organisms

the process of binary fission

• 1) the cell replicates its DNA

• 2) the cytoplasmic membrane elongates, separating the DNA molecules

• 3) cross wall forms, the membrane invaginates

• 4) cross walls form completely

• 5) two daughter cells are created

common features for all cells

• plasma membrane, cytoplasm, nucleic acids, ribosomes

prokaryote cells

unicellular, lack membrane bound organelles,

specialized structures of prokaryote cells

• flagella: tail life extensions, allow for movement

• pili: allow for genetic transfer

• fimbriae: important for attachment to surfaces

eukaryotic cell

• unicellular (yeast) or multicellular (plant or animal cells), has lots of membrane bound organelles

structures unique to plant cells

• cell wall, chloroplasts, plant vacuoles, and plastids

structures unique to animal cells

• centrioles, lysosome

common features for plant and animal cells

• plasma membrane, nucleus, endoplasmic reticulum, ribosomes, golgi bodies, mitochondria, vesicles, centrosome, cytoskeleton

mitochondria

• powerhouse of the cell, makes energy, site of cell respiration (produces ATP),

chloroplasts

• takes energy from the sun to convert it into glucose, the site of photosynthesis, consists or stroma (fluid) and grana, commonly found in the cells of leaves

the cell theory

• all living things consist of at least one cell

• all cells arise from pre-existing cells

• cells are the smallest structural unit of life

SA:V

• an important factor in the limitations of cell size and the need for organelles:

• smaller cells have a larger SA:V making it easier to exchange nutrients

• larger cells are less efficient

the fluid mosaic model

• a way to describe the composition and structure of the plasma membrane

fluid in terms of the fluid mosaic model

• the molecules within the plasma membrane are able to move, important for transport across the membrane

mosaic in terms of the fluid mosaic model

• the membrane is composed of many different molecules

the function of the plasma membrane

• to control what goes in and out of the cell, separates the extracellular environment from intracellular, allows cells to recognise each other, membranes also exist outside of the cell to establish components

phospholipid

• naturally arrange themselves in a bi-layer due to the chemical properties of the head and tail, has a hydrophillic head and a hydrophobic tail

cholesterol

• regulates fluidity of the membrane and reduces permeability, embedded in membrane, regulates temp in hot (prevents phospholipids from packing too tightly), and cold (prevents them from spreading apart)

proteins in the plasma membrane

• peripheral = loosely attaches, important for cellular communication

• integral = embedded in the membrane, important for transport

carbohydrates

• important for cellular communication and maintaining membrane structure

• glycoproteins = carbohydrate chain attached to a protein

• glycolipids = carbohydrate chain attached to lipid

passive transport

• no energy required, molecules move along their concentration gradient from high to low, there are different types depending on size and chemical properties

simple diffusion

• the passive movement of a substance across a differentially permeable membrane along the concentration gradient, this is affected by:

• permeability of the membrane, surface area, concentration gradient, and the distance of diffusion

osmosis

• the passive net movement of water molecules through a differentially permeable membrane from an area of low solute to high solute - the pressure that makes water move is osmotic pressure

hypotonic solution (osmosis)

• more solute inside the cell, the water moves into the cell and the cell enlarges

isotonic solution (osmosis)

• equal concentration of solute inside and outside of the cell, no net movement

hypertonic solution (osmosis)

• less solute inside the cell, water moves out of the cell and the cell shrinks

facilitated diffusion

• the passive net movement of a substance through a protein channel (doesn't change shape, smaller substances) or a carrier protein (the molecule causes the protein to change shape, allowing the molecule to leave the other side)

active transport

• energy requires, molecules move against their concentration gradient (in a way there not usually meant to go in) from low to high concentration

protein pump (active transport)

• the active transport of a substance against the concentration via a protein pump, the pump changes shape (due to ATP) to allow molecules to pass through

endocytosis (bulk transport)

• enables the transport of macromolecules (large molecules) into the cell, there are three main types:

• phagocytosis (cell eating) = for large solid molecules such as food particles or bacterial cell

• pinocytosis (cell drinking) = for liquids

• receptor mediated endocytosis = a form of pinocytosis triggered by cell receptors on the plasma membrane

exocytosis (bulk transport)

• the exit of large molecules from the cell

• the vesicle carrying molecules for the export moves to the perimeter of the cell

• vesicle fuses with the plasma membrane

• the contents of the vesicles are expelled into the intracellular space

secretory pathway

• the pathway from producing proteins to them exiting the cell, involves golgi body and er

how does the structure of the mitochondria assist

• has a double membrane, inner (cristae) that provides a large SA for the production of ATP

how does the structure of the chloroplast benefit

contain chlorophyll to capture sunlight for photosynthesis