Unit 1: Cell Biology Review

What are the 3 parts to “Cell Theory”?

1. Cell is the smallest unit of life

2. All cells come from preexisting cells

3. All living things are made up of cells

What are the common characteristics in cell?

• Have a membrane that separates the internal/external environment.

• Genetic material that instruct cell’s activities

• Energy is released to power activities

What are some atypical examples?

• Striated muscle : made up of fibers similar to cells, larger than most cells, and multiple nuclei.

• Aseptate fungal hyphae: thread-like structure, many nuclei, but not new or different cells.

• Giant algae: one cell with one single nucleus that grow to 100mm. Usually cells this large divide in more cells. ex: Acetabularia

• Red- Blood cells: Do not have a nucleus

What the characteristics of electron microscope?

• high resolution

• See small distance between the cells or 2 objects

• Beam of electron

• Non-living organism

What the characteristics of light microscope?

• Uses light.

• Low resolution

• Organism (can be) alive.

What the magnification formula?

• Size of image/ actual size of specimen

• Know your units.

What are unicellular organism?

• An organism has one cell that can carry out all functions of life.

What are the functions of life? (unicellular)

• Nutrition : obtaining food for energy and growth

• Growth: increase in size

• Metabolism: chemical reaction, releasing energy.

• Response: adapt and react to changes in the environment.

• Homeostasis: keeping internal environment within tolerable limits.

• Reproduction: producing offspring sexually or asexually.

• Excretion: removes waste products of metabolism.

Paramecium Functions of Life

• Found in pondwater.

• Reproduction: Nucleus divides to produce the extra nuclei when the cells reproduce. (Asexual reproduction)

• Nutrition: Food is kept in the vacuoles (contain small organism that are consume. They get digested and the nutrients is absorbed into the cytoplasm. Energy provides growth for the unicellular organism.

• Excretion: Cell’s membrane control what enter and leaves. Allows oxygen for respiration. Waste products are diffuse out of the membrane.

• Homeostasis: Contractile vacuoles at each end of the cell fill up with water then expel it through the plasma membrane. This happens to keep cell’s water content within its limits.

• Metabolism: Metabolic reactions take place in the cytoplasm, including the reactions that releasing energy by respiration. Enzyme catalyst these reactions.

• Response: Beating of cilia moves it through the water. This can be controlled by the cells, so that it moves to a particular direction response to the environment.

Chlamydomonas Function of Life?

• Unicellular alga that lives in freshwater and soil

• Not a true plant, even though it goes through photosynthesis, green, and its cell wall isn’t made up of cellulose.

• Reproduction: Nucleus of the cell divide to produce identical nuclei for asexual reproduction.

  • Nuclei can fuse and divide to carry out sexual reproduction.

  • Nucleus is concealed by chloroplasts.

• Metabolism: Metabolic reactions take place in the cytoplasm. Enzyme speeds them up.

• Excretion: Cell wall is freely permeable. Also, the membrane that inside, controls what chemical leaves and enter the cell.

• Homeostasis: The contractile vacuoles at the base of the flagella. They are fill up with water. Then it is expelled through the plasma membrane of the cell, to maintain cells tolerable limits.

• Nutrition: Photosynthesis occurs inside chloroplasts in the cytoplasm.

  • Carbon Dioxide is converted into compounds needed for growth.

  • Other carbon compounds are absorbed through the cell membrane.

• Response: Beating of the two flagella moves the Chlamydomonas through the water. Light sensitive “eyespot” allows for the cell to sense where the brightest light is and respond by swimming towards it.

What Surface Area to Volume Ratio?

• The smaller the cell, the greater surface area to volume ratio

• As the cells grows, the surface area to volume ratio decreases.

  • Greater ratio allows for more better transfer of materials.

Continued of Surface Area to Volume Ratio?

• Without cell division to keep cells smaller, this makes it a lot harder for materials to transfer. Materials such as waste and heat can’t be transferred as fast enough.

  • Rate of exchange is the function of its surface area.

  • The rate of production of heat, waste, carbon dioxide, and oxygen are function of its volume.

    • Volume of a cell determines requirements while surface area determines supply. 

Multicellular Organism?

• Cells differentiate to carry out special functions. Each cells have the same DNA, but different genes are expressed to give them their specialized functions.

• Emergent Properties: Different cells interact with watch other to allow for more complex functions. Do more work together, rather than alone.

• Caenorhabditis elegans is a 1mm worm that has 959 cells working together and humans have 220 different types of specialized cells.  

  • The whole is greater than the sum of its parts

    • Individual neurons are not capable of thought but communication and cooperation of neurons allow the brain to think.

What are Stem Cells?

Undifferentiated cells, they have the ability to divide into various cell types.

• Also used to repair and replace tissues.

• Occurs down different pathways: totipotent, pluripotent, multipotent, & unipotent.

• Ethic concerns: death of embryos to obtain stem cells. (IVF PROCESS)

Benefits of Stem Cells?

• Stargardt’s Disease- macular dystrophy (degeneration of the retina); Stem cells have been used to replace damaged cells in eye with positive results.

• Leukemia- blood stem cells have been used to replace damaged bone marrow caused by treatment.

Embryonic Stem Cells Functions?

• Almost unlimited potential

  Any cell in the body

  Risk of tumors

  Less chance of genetic damage form accumulated mutations.

  Genetically different than patient receiving them.

  Kills embryo unless only 1 or 2 cells are taken.

Cord Stem Cells?

 

Easy to get and store.

Collection/ storage services available

No rejection

Limited capacity- only develops into blood cells.

Limited quantities from one baby

Cord discarded with or without cells taken.

Adult Stem cells?

 

Difficult to obtain- deep in tissue.

Less growth potential

Less chance of tumor developing than from embryo

Limited capacity

No rejection

Removal does not kill adult that they are taken from

Prokaryotic Cell Structures and Functions?

• Cell wall- not cellulose

• Naked DNA- no proteins

• Plasma membrane

• Cytoplasm

• Ribosomes- smaller than eukaryotes

• Pili- attach to surfaces and other bacteria

• Flagella- movement/ motility

• Reproduces through binary fission cells are made identical.

Eukaryotic Organelles and Functions?

• Nucleolus- produce ribosomes and RNA nucleotides

• Nucleus- house genetic material

• Ribosome- protein synthesis

• Rough Endoplasmic Reticulum- houses ribosomes; protein synthesis on ribosomes & forms vesicles for transport out of cell or to Golgi Apparatus

• Smooth Endoplasmic Reticulum- detoxification

• Golgi Apparatus- specialize and package proteins, forms vesicles for transport. 

• Lysosome- intracellular digestion

• Microtubules- structural support & movement

• Mitochondria- aerobic respiration 

• Chloroplast- photosynthesis

• Central Vacuole- similar to lysosome but in plants, storage of water and waste

What is the difference between Prokaryotic vs Eukaryotic?

In the prokaryotic cell:

• Genetic material in a loop of DNA located in cytoplasm

• Naked DNA

• Mitochondria not present

• Ribosomes small (70S)

• Few or no organelles present

In Eukaryotic cell:

• Genetic material in strands of DNA located in a contained nucleus

• Chromosomes of DNA and proteins

• Mitochondria always present

• Ribosomes large (80S)

• Many organelles to compartmentalize functions

Comparing Plant & Animal Cells?

Plants:

• Cell wall of cellulose

• Large central vacuole- large; similar to lysosome

• Chloroplasts for photosynthesis

• No centrioles

• Rigid shape

• Carbohydrates stored as starch.

Animals

• No cell wall.

• No large central vacuole

• No chloroplast

• Centrioles

• Globular shape

• Carbohydrates stored as glycogen.

Davason-Danoelli Model

• Early freeze etched micrograph images show two dark lines with a lighter area between them.  Prior to this, it had been concluded that the membrane was made up of a bilayer of phospholipids (Gorter and Grendel).  In electron micrographs, proteins appear dark and phospholipids light.  Davson & Danielli proposed that a layer of proteins was on either side of the bilayer to explain this and allow for the membrane to be very thin but still an effective barrier.

Falsification of the Davson-Danielli Model

Since then, proteins have been able to be extracted and shown to be varied in size and globular.  These are not likely to be able to form the proposed continuous layer on the periphery.  Also, at least a part of them was hydrophobic and would have been attracted to the fatty acid tails in the center.

Later, fluorescent tags (red and green) were used to bind to membrane proteins and showed that they were mixed throughout free to move rather than fixed on the periphery.

What are Phospholipids?

-amphipathic: (hydrophobic and hydrophilic parts

• Hydrophilic head groups point outward.

  • Hydrophobic tails form a lipid bilayer to form a

  (phospholipid) bilayer

  • Ions and polar molecules cannot pass through.

  hydrophobic barrier

  • Helps the cell maintain internal concentration and exclude other molecules.

Is cholesterol also amphipathic?

• Maintains consistency of plasma membrane in heat and cold.

• Mostly hydrophobic and situate around the fatty acid tails, but also have a hydroxyl that is hydrophilic and situates between phosphate heads.
  

What are some glycoproteins?

They identified Cells.

• Cell ID tags

  • Embryos

  • Immunity

What is a membrane protein?

• embedded in the membrane.

• Some extend from one side to another.

What is the function of membrane protein?

• Serve as channels for passive-transport: Hydrophilic particles by facilitated diffusion.

• Hormone binding site ex: Insulin receptor

• Enzymes: active site on the outside ex small intestine

• Pump for active transport: use ATP and change shape.

• Cell adhesion: between tissues and organs.

• Cell to cell communication: Neural receptors for neurotransmitter synapses.

What are the types of diffusion?

1. Simple diffusion

2. Facilitated Diffusion

3. Osmosis

What’s simple diffusion?

• the movement of particles from a high concentration to a low concentration.

• Greater difference in concentration = faster rate of diffusion

• Charge and large molecules cannot bass without the transport of a protein.

What’s Facilitated Diffusion?

• Large and charged molecules can still move by diffusion but require a transport protein to facilitate them through the plasma membrane.

What is Osmosis?

Diffusion of water, from high to low solvent or low to high solute

Semi-permeable membrane require.

What is Isotonic, hypertonic, hypotonic?

• Isotonic: no water movement

• Hypertonic: Water moves out, cells shrink

• Hypotonic: water moves, outward pressure, eventually burst.

What is Active transport?

Membrane protein is use in the energy form ATP to pump molecules from areas of low concentration to high. This goes against the concentration gradient causing the protein to change shape in the process.

What is the vesicles?

• a vesicle is made by pinching off piece of membrane, this is because of fluidity.

• Transport materials around the inside of cells.

• vesicles transport proteins from the RER to the Golgi Apparatus then to the Plasma membrane.

What is Endocytosis?

• Material Membrane encloses around target particles? (phagocytosis)

• Fluidity allows it to happen.

• Membrane sinks inwardly, a pit forms and the membrane seals back on itself, membrane layer encloses particle forming a vesicle.

• Vesicle breaks away from the membrane and moves into cytoplasm.

What is the exocytosis?

• Vesicles carry materials to the membrane, and it then fuses with it.

• Because of fluidity

• Material expelled/ secreted from the cell.

• Membrane, with phospholipids from vesicle flattens.

What are the 4 processes required to the origin of cells?

1. Non-living synthesis of simple organic molecules through chemical reactions.

2. Formation of organic molecules into polymers

3. Polymers have the ability to self-replicate, so inheritance is possible.

4. Molecules are pack into the membranes to separate internal chemistry from their surroundings. Phospholipids or other amphipathic carbon compound will form a bilayer.

What were the origin of organic compounds?

• Area such as deep-sea hydrothermal vents or volcanoes.

  • In water, organic reactions are aqueous.

  • Warm conditions allow for high reaction rates.

  • Organic molecules became more concentration with the evaporation of water.

  • Clay minerals act as a catalyst.

Pasteur’s Experiment for Spontaneous Generation

Life appearing from nothing.

• Broth was placed in both flasks and boiled to kill any organisms in it.  

  • *No clouding or growth in (1) because curved neck allowed exposure to air but prevented entry

    of microbes.

  • *Clouding or growth occurred in (2) because microbes from the air contaminated it once the neck was broken off

  • *Broth that was not boiled was also used as a control with fungi and other organisms appearing.

  
  

What was miller and Urey experiment?

• Took elements from that were in the atmosphere and oceans of pre-biotic earth.

• Electrical discharges were added to stimulate lighting.

• Organic molecules (amino acid) were found in the “soup” produce by the experiment.

• his led to later similar experiments that produced adenine (present in DNA, RNA, and ATP)

Endosymbiotic Theory?

• Some eukaryotic organelles developed from prokaryotes.

• Mitochondria and chloroplasts share several characteristics with prokaryotes so it is believed that they once were prokaryotes that were engulfed by endocytosis.  They were not digested but became an organelle of eukaryotes.

  • They have their own smaller 70S ribosomes 

  • They have circular DNA

  • Transcribe their DNA and use mRNA to make their own proteins

  • Replicate themselves by binary fission

  • Have their own double membrane surrounding them

  • Similar size and shape as prokaryotes

• The ability to produce organic molecules through photosynthesis and make ATP were valuable characteristics.

RNA as original Genetic Material?

Early cells needed a molecule that can form polypeptides that can be used to catalyze reactions and re itself.