unit 3, chapter 2 biology

7/30/2019 Unit 3, Chapter 2 Biology

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- Apoptosis, or programmed cell death, is self-destruction by cells for the good of the wholeorganism.

- Necrosis : occurs if a cell is seriously damaged by mechanical or chemical trauma and causesgeneral damage to plasma membrane of cell

Plasma membrane can no longer control what enters of leaves the cellsCell swells then burst and contents spread out over nearby cells, causing inflammation of those tissues.

- Apoptosis : cells respond to signals2 main pathways of signals that initiate apoptosis

1. Mitochondrial pathway2. Death receptor pathway

Mitochondrial pathway:- Signals from inside the cell- If serious damage occurs inside a cell (severe DNA damage/malfunction of oxidative enzyme)

proteins on surface of mitochondria activated and mitochondrial membrane breaks- Starts series of events in cell: action of caspases (special enzymes that cleave specific proteins at

amino acid aspartite ) enter nuclear pores and break DNA into smaller pieces- Cell infected with virus may also initiate death

Cell identifies infection and kills before virus replicates and spread to other cellsDeath receptor pathway:- Signals from outside the cell.

- Perfectly healthy cell receive message of self-destruct.- Not fully developed:Cells fail to be incorporated into brain networkStray cells die by apoptosis

- Excess cells dieCost organism energy and material to keep cells aliveMore cells than necessary

- Cells no longer useful to an organism dieWhen recovered from a disease, cells no longer require T and B cells produced

Disease and apoptosis:- Apoptosis is an essential feature of development- A healthy state relies on balance between cell production and cell loss in organism.- Too much apoptosis can lead to neurodegenerative diseases: Alzheimer and Huntingtons disease- Too little apoptosis can lead to production of cancers and autoimmune diseases


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- When a message is received, acascade of events occurs:

1. Many different caspases are activated within thecell and a message goes out to phagocytes in thearea

2. Cells that received the death signal being to

shrink and develop small bumps (blebs) onsurface3. Caspases enter through nuclear membrane

pores, DNA and protein in nucleus degraded,mitochondria break down

4. Organelles (other than nucleus and mitochondria)preserved as cell breaks into small membraneenclosed fragments

5. Small fragments bind to receptors on phagocyticcells that have responded.

- Phagocytes engulf fragments- Secrete cytokines (compounds that

inhibit inflammation) so surrounding cells notdamaged


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- Each living cell is a small compartment with an outer boundary: plasma membrane- Cytosol: fluid that makes up a living eukaryotic cell consist mainly of water and many dissolved

substances- A labyrinth of membranes within cytosol that create large number of smaller functional distinct

compartments- Organelles : membrane-bound compartments structures present in a cell and which carry out a

specific function- Organelles held in place by a network of fine protein filaments known as cytoskeleton- Prokaryotic cells (bacteria) lack internal membranes.


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- The boundary of all livings cells is a plasma membrane that controls the entry of dissolvedsubstances into and out of the cells.

- Plasma membrane ultra-thin and liable layer with average thickness (0.000 01mm)- Plasma membrane too thin to be resolved with light microscope but can be seen using electron

microscope- Comprises of phospholipid bilayer: proteins and glycoproteins protrude- Some protein embedded in layer form channels that allow certain substances to pass across

membrane in either direction fluid mosaic model

- On outer surface, plasma membrane has substances (antigens) that label/identify cells asbelonging to a particular organism.

- Antigens : compounds, usually proteins, that can trigger the immune system to respond in variousways, including antibody production.

Usually consist of proteinsWhen various mammals of same species compared, antigens on plasma membrane differ.

- Cells from one organism introduced into body of other species immune system recognizes cellsas foreign or non-self

- Immune system responds with chemical and cellular attacks that kill foreign cells.- Immune system does not normally attack own cells recognize cells as self- Ability to recognize foreign cells and attack them is an important defence mechanism against

bacterial infection.

- All cells must be able to take in and expel various substances in order to grow, survive andreproduce

- Generally substances in solution, but also tiny particles- Partially permeable: plasma membrane allows only some dissolved materials to cross


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- Diffusion: net movement of a substance, typically in a solution, from a region of high concentrationof the substance to a region of low concentration.

Does not require energy- Molecules in random movement at all times- If substance more concentrated outside cell, molecule move from outside to inside- Diffusion stops when concentration of substance is equal on both sides of membrane- Substances that dissolve easily: hydrophilic or water-loving

- Substances with low water solubility or do not dissolve in water are able to dissolve in or mixuniformly with lipid lipophilic or hydrophobic (alcohol or ether)Lipophilic substances cross plasma membrane boundaries readily.

Channel mediated:- Substances unable to carry out simple diffusion through phospholipid bilayer gain free passage

across membrane with assistance of protein channels- Molecules move from high concentration to low concentration without energy.Carrier mediated:- Protein channel alone insufficient and carrier molecule required to move molecules down

concentration gradient through protein channel.- When specific carrier molecule is required, movement called facilitated diffusion- Movement of substances by facilitated diffusion mainly involves substances that cannot diffuse

across the plasma membrane by dissolving in the phospholipid bilayer of the membrane.Movement of glucose molecules across plasma membrane of red blood cells involves specificcarrier molecule.

- All 3 methods of passive transport result in molecules moving from region of high concentration toregion of low concentration without using energy.

- One special case of diffusion is known as osmosis. The process of osmosis occurs when a net movement of water molecules occurs by diffusionacross a cell membrane either into or out of a cell.

- Active transport: net movement of dissolves substances into or out of cells against aconcentration gradient

Net movement of dissolved substances across a cell membrane by an energy-requiringprocess that moves substances against a concentration gradient from a region of lower tohigher concentration.

- The process involves a carrier protein for each substance that is actively transported.


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- Solid particles can be taken into a cellOne kind of white blood cells able to engulf disease-causing bacterial cell and enclose it withina lysosome sac where destroyed.Unicellular protists (amoeba and paramecium) obtain energy in form of relatively large foodparticles

- Endocytosis: process of bulk transport of material into a cell- Exocytosis: bulk transport out of cells.

Vesicles form within a cell fuse with plasma membrane before contents of vesicles from thecell.

Term secretion form the cell generally used if released material product of cell. Term voided from the cell generally used if released material waste product of cell.

- Rigid cell wall forms exterior of plant, fungi andbacteria.

- Cell wall lies outside plasma membrane- Primary cell wall: made of cellulose

In certain plants, primary cell wall in certaintissues become thickened and strengthened.


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- Secondary cell wall : made of lignin in addition to celluloseProvide great elastic strength and supportAllow plants to develop woody shrubs or trees


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- Nucleus : in eukaryotic cells, a membrane-bound organelle containing the genetic material DNA The control center of cells of animals, plants, algae and fungi

- Form distinct spherical structure enclosed in double membrane- Nuclear envelope : membrane surrounding the nucleus of a eukaryotic cell.- Cells that have a membrane-bound nucleus are called eukaryotes

- Prokaryotic cells : any cell without a membrane-bound nucleus.Cells that lack nuclear envelope

- Kingdom Monera (bacteria)- DNA not enclosed within distinct nucleus

- Light microscope:Nucleus contains granules made of DNA.DNA dispersed within nucleusDuring cell reproduction, DNA granules become organized to rod-shaped chromosomesNucleus contain one (or more) large inclusion known as nucleoli

- Nucleoli : aggregation of ribonucleic acid (RNA) molecule.

- Living cells use energy all the time- Adenosine triphosphate (ADP): compound containing adenine and two molecules of

phosphate; in an energy-requiring reaction, it can combine with a third molecule of phosphate toform ATP.

Usable energy supple for cells- ATP produced during cellular respiration (respiration)- ATP supplies in living cells continually being used and replaced- Eukaryotic cells: ATP produced in mitochondria (mitochondrion)

- Mitochondria (mitochondrion): in eukaryotic cells, organelles that are the major site of ATPproduction.

- Cannot be seen under light microscope but electron microscope

- Outer membrane and highly folded inner membrane- ATP produced by reactions in inner folded membranes.- Prokaryote cells lack mitochondria


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- Ribosomes : organelles where protein production occurs- Only be seen only through an electron microscope

- Ribosomes not enclosed by membrane

- Ribosomes attached to endoplasmic reticulum and found incytosol.- Proteins produced by ribosomes on rough endoplasmic

reticulum transported to and from other parts of cell.- Proteins made by free ribosomes (unattached to ER) for

local use within cell.- Mitochondria and chloroplast contain free ribosomes.

- Ribosomes composed or protein and ribonucleic acid (RNA)- Ribosomal RNA (rRNA) come form nucleolus in cell.- Particular part of DNA carries genetic code necessary for

formation of ribosomal and other RNAs.

- Proteins kept within cells:Contractile proteins (muscle cells)Haemoglobin (red blood cells)

- Proteins released to other cells:Digestive enzyme pepsin (lining of stomach and released into stomach cavity)Protein hormone insulin made by pancreatic cells and released to bloodstream

- Transport and substances within cells occur through system of channels known as endoplasmicreticulum.

- Golgi complex : organelle that packages material into vesicles for export from a cell.Several layers on membranes

- 1. Proteins produced by ribosomes go to membranous chambers in ER.- 2. Packaged into vesicles and transported to Golgi complex where they may be concentrated


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- Ribosomes ER vesicles Golgi complex- In Golgi complex, proteins packaged into secretory vesicles.- Protein stored in cytosol then fuse with plasma membrane- Protein discharged by exocytosis into tissue fluid- Protein taken by other cells or into bloodstream (transported to other tissues)


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- Lysosomes : membrane-bound vesicles containing digestive enzymes.Sac-like structure surround membrane with fluid containingdissolved digestive enzymes.

- Use enzymes to destroy unwanted cell parts of damages molecules fromwithin or outside the cell

- Unwanted material enclosed by lysosome and digested

- Lysosomes: controlled death zone of cells in embryonic human hand sofingers become separated.

- Produced enzymes that digest substance- Defects may occur in enzymes in lysosomes

Substance accumulate in lysosome cell no longer function Tays Sachs disease (abnormal accumulation of lipids)Hurler syndrome (abnormal accumulation of complex carbohydrates)

Peroxisomes and endosomes: small organelles with similarities as lysosomes in eukaryoticcells.

- Small membrane-bound organelles in enzymes catalase and urate oxidase.- Detoxify various toxic materials in bloodstream- Hydrogen peroxide (H2O2) biochemical process in cell poisonous if accumulate.- Peroxide in different type of cells may contain different set of enzymes.- Plant and animal cells

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- Accumulation of hydrogen peroxide prevented catalyst.

- Only in animal cells- Membrane-bound organelles- Pass newly ingested material to lysosome for digestion- Material enter cell by endocytosis.


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- Chloroplast : organelle (plant/algae) capture radiant energy of sunlight and transform to chemical

energy in organic molecule- Photosynthesis : complex proves of converting sunlight energy to chemical energy present insugar.

- Double membrane (inner and outer)- Inner: form membranous sacs lamella or thylakoids

Stacked together to form grana- Grana: chlorophyll located.

Light-dependent reactions of photosynthesis- Stroma : semi-fluid substance contain enzymes for light-independent reactions

-- Prokaryotes dont have chloroplast- Photosynthetic bacteria: some bacteria have pigment that enable to capture radiant energy of

sunlight make sugar from simple inorganic material.- Chloroplast contain molecule of DNA, free ribosome, starch grains and lipid droplets


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CELL SKELETON:- Internal f ramework:

MicrotubulesMicrofilamentsIntermediate filaments.

- Cytoskeleton : supply strength and supportNetwork of filaments within a cell.

- Microtubules : hallow


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- Acts throughout group of cell

- Rigid cell walls and primary walls of adjacent cells held tightly by layer of pectine (stickypolysaccharide). Hence, plant cells have no need for structure such as anchoring junctions of animal cells.

- Secondary walls laid in each cell on cytosol side of primary wall structure relatively wide- Junctions allow plant cells to communicate plasmodesmata

Openings between plant cell walls through which adjacent cells are connected throughcytoplasmic threads.

- Gap lined with plasma membrane to plasma membrane of two cells continuous.- Also continuous with smooth endoplasmic reticulum

- Plasmodesmata in all plants- Communication between large number of cells- Connected via cytoplasm

- Cells connect and transfer of material and messages occur through connections.

unit 3, chapter 2 biology

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