Modern Cell Theory:
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Prokaryotes: have no nucleus or other internal membranes
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Eukaryotes: have a nucleus and are more complex cells
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Where did cells come from?
Earth is about 4.6 Billion years old; all organisms are believed to have derived from a prokaryotic cell 3.5 Billion years
Earth is about 4.6 Billion years old; all organisms are believed to have derived from a prokaryotic cell 3.5 Billion years
Although we typically look at bacteria, plant, and animal cells, all cells do not all look alike. A cell's form is due to its function... (Ex: a nerve cell function is to conduct electrical impulses, therefore it has long axons. The human body has over 200 different types of eukaryotic cell types, each with a different function...and each cell types has a different form.
Even though cell types have different functions, they have the same organelles.
Even though cell types have different functions, they have the same organelles.
Plant Cell
Animal Cell
Mitochondria:Chloroplast:Amoeba's pseudopod..
Plasma Membrane
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Cell Organelles:
- Chromosomes contain genes (parts of DNA that code for proteins) - Surrounded by a selectively permeable membrane with pores to allow transport of molecules such as RNA out of the nucleus and into the cytoplasm
- tangles of chromatin in this region
- made up of ribosomal RNA and protein - suspended in cytoplasm or bound to the ER - a human liver cell that produced much protein has millions of ribosomes
- ROUGH ER= site for protein synthesis and transport - SMOOTH ER= synthesizes steroid hormones and other lipids
- secretes these substances to other parts of the cell and to the cell surface to export OUT to other cells
- plant cells don't always have lysosomes
- a very active cell has over 2,500 mitochondria - consist of an outer double membrane and a folded inner membrane (cristae) - mitochondria contain their own DNA and can self-replicate - ATP synthetase is found inside the mitochondria - this is the enzyme that will make ATP
- a contractile vacuole will PUMP excess water out of the cell - plant cells and human fat (adipose) cells have large central vacuoles for storage
- found in axon of a nueron- they release neurotransmitters (chemical signals) into a synapse
- site for photosynthesis - contain their own nuclear membrane and can self-replicate
- Two centrioles at a right angle = centrosome
- cilia are short, flagella are long
- cell walls in fungi= made of chitin - cell walls in plants and algae = made of cellulose
- Cytosol: semiliquid portion of the cytoplasm - Cyclosis: movement of organelles in eukaryotes around the cell
- "fluid mosaic model because made of many different particles that can move around - Phospholipid bilayer with proteins dispersed in it - molecules of cholesterol making it less fluid and more stable - carbohydrate chains are in the outside for cell to cell recognition - 60% proteins; proteins act as enzymes (like APT synthetase), some are pumps (like in the sodium potassium pump) |
Transport Into and Out of the Cell
Terms:
- selectively permeable: the cell membrane will allow certain molecules to easily pass through based on size, and other molecules, such as ions, based on the need of the cell.
- solvent: the substance that does the dissolving
- solute: the substance that dissolves
- hypertonic: having greater concentration of solute than another solution
- hypotonic: having lower concentration of a solute than another solution
- isotonic: two solutions containing equal concentrations of solute
Passive Transport
Passive Transport: no energy required; movement from high concentration to low concentration
DIFFUSION & Facilitated Diffusion-
OSMOSIS- the diffusion of water
Simple diffusion: the movement of molecules from high to low concentration; the steeper the GRADIENT, the faster the rate of diffusion.
EX: earthworm "breathe" as oxygen from is air is absorbed by simple diffusion across their moist skin into capillaries beneath the skin
EX: humans obtain oxygen by simple diffusion across moist membranes in air sacs (called alveoli) in the lungs
DIFFUSION & Facilitated Diffusion-
OSMOSIS- the diffusion of water
Simple diffusion: the movement of molecules from high to low concentration; the steeper the GRADIENT, the faster the rate of diffusion.
EX: earthworm "breathe" as oxygen from is air is absorbed by simple diffusion across their moist skin into capillaries beneath the skin
EX: humans obtain oxygen by simple diffusion across moist membranes in air sacs (called alveoli) in the lungs
Facilitated Diffusion: relies on membrane protein channels to assist in transporting specific substances across the membrane but still NO ENERGY is required for this process.
EX: neurons require calcium ions to be transported by facilitated diffusion through the calcium ion channels on the axon membrane |
Osmosis: diffusion of water across a membrane; water flows DOWN the concentration gradient toward a region with high SOLUTE concentration.
Ex: cell A has more solute than cell B; cell A is hypertonic to cell B and cell B is hypotonic solution
plasmolysis: when water leaves the cell causing the cell to shrink
turgor pressure: when a Plant cell fills with water due to a hypotonic solution, it will swell and have pressure on its cell walls (in animal cells, when cell fills too much with water, it will burst, called lysis)
isotonic solution: a solution that results in no net change in the amount of water inside or outside a cell (equilibrium has been reached)
Ex: cell A has more solute than cell B; cell A is hypertonic to cell B and cell B is hypotonic solution
plasmolysis: when water leaves the cell causing the cell to shrink
turgor pressure: when a Plant cell fills with water due to a hypotonic solution, it will swell and have pressure on its cell walls (in animal cells, when cell fills too much with water, it will burst, called lysis)
isotonic solution: a solution that results in no net change in the amount of water inside or outside a cell (equilibrium has been reached)
Active Transport: energy is required; movement from low concentration to high concentration.
Receptor Mediated Endocytosis- a cell can take up large quantities of a very specific substance
- extracellular substances bind to specific receptors on the cell membrane and are drawn into the cell by vesicles - this is how the body cells take up cholesterol from the blood. |
Sodium- Potassium Pump carries particles or ions across the membrane against the concentration gradient. Sodium potassium pump in nerve cells carry Na+ and K+ across the axon membrane to make the nerve return to a resting state after and impulse signal has passed.
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Technology to study cells
ultra centrifuge: isolate components of cell
cell fractionation (larger components separate from smaller ones)
freeze fracture: study details of membrane structure under the electron microscope (makes cast of the cell)
tissue culture: allow cells to live in the petri dish to be studied in vivo!
cell fractionation (larger components separate from smaller ones)
freeze fracture: study details of membrane structure under the electron microscope (makes cast of the cell)
tissue culture: allow cells to live in the petri dish to be studied in vivo!
Notes: (* Notes and Powerpoints adapted from Shannan Muskopf's fantastic teaching resource: Biology Corner.)