Transcript CELLS
CELLS • All organisms are made up of cells • The cell is the unit of structure and function of all living things • Life arises from the interaction of all cellular components. You must check this web site • www.cellsalive.com There is correlation between the structure of cells and their function Ex: The shapes of muscles cells, sperm cells, red blood cells,, nerve cells are appropriate for their function. Example: the flat tile like epithelial cells of the skin fit closely together making a barrier to bacterial entrance, water loss etc. Another way to say this is that “shape reflects function” 10 m Most cells are microscopic Length of some nerve and muscle cells 100 mm (10 cm) Chicken egg 10 mm (1 cm) Frog egg 1 mm 100 m Most plant and animal cells 10 m Nucleus Light microscope Most bacteria 1 m Mitochondrion Mycoplasmas (smallest bacteria) 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms Electron microscope – Cells vary in size and shape Human height 1m Unaided eye How small are cells? History • Robert Hook (1665) named “cells” after observing tiny compartments in cork . • Anton VanLeeuwenhoek (1600’s) improved the primitive microscopes and observed one celled organisms, even bacteria. He documented his findings with letters and diagrams to the Royal Society (of Science) in London. • Robert Brown (1600’s)discovered the nucleus • Electron microscope was developed in the late 1930’s and allows scientist to see up to 0.5 nanometers. About 1000 times larger than regular microscopes. How are cells studied? Microscopes and Biochemistry – The light microscope (LM) magnify cells up to 1000 times • Enables us to see the overall shape and structure of a cell Eyepiece Ocular lens Objective lens Specimen Condenser lens Light source Figure 4.1A – The electron microscope Figure 4.1C TEM 2,800 SEM 2,000 • Allows greater magnification and reveals cellular details Figure 4.1D The cell theory (mid-1800’s) • Mathew Schleiden and Theodor Schwann examined plant and animal tissues and came to the conclusion that they both consist of cells • Rudolph Virchow came to the conclusion that young cells come from the division of other cells • 1. All organisms are made up of cells • 2. Cells are the units of structure and function of all living things, that is cells have all the properties of life. • 3. All cells come from pre-existing cells • Prokaryotic cells are structurally simpler than • eukaryotic cells – There are two kinds of cells • Prokaryotic- No nucleus- Colorized TEM 15,000 Bacteria and Archeae • Eukaryotic- have nucleus- plants, animals and fungi Prokaryotic cell Nucleoid region Nucleus Figure 4.3A Eukaryotic cell Organelles – TYPE OF CELLS: Prokaryotic and Eukaryotic – Prokaryotic cells are small, relatively simple cells • That do not have a membrane-bound nucleus Prokaryotic flagella Ribosomes Capsule Cell wall Plasma membrane Nucleoid region (DNA) Pili Eukaryotic cells have a nucleus and are partitioned into functional compartments. – All other forms of life( plants and animals) are composed of complex eukaryotic cells – Membranes form compartments inside eukaryotic cells to facilitate metabolic activities – A small cell has a greater ratio of surface area to volume • Than a large cell of the same shape 10 m 30 m 30 m Surface area of one large cube 5,400 m2 10 m Total surface area of 27 small cubes 16,200 m2 – A typical animal cell • Contains a variety of membranous organelles Smooth endoplasmic reticulum Nucleus Rough endoplasmic reticulum Flagellum Not in most plant cells Lysosome Ribosomes Centriole Peroxisome Microtubule Cytoskeleton Golgi apparatus Plasma membrane Intermediate filament Mitochondrion Microfilament THE CYTOSKELETON AND RELATED STRUCTURES The cell’s internal skeleton helps organize its structure and activities – A network of protein fibers • Make up the cytoskeleton. Tubulin subunit Actin subunit Fibrous subunits 7 nm Microfilament 25 nm 10 nm Intermediate filament Microtubule Functions of the cytoskeleton – Tubules and filaments are made up of protein fibers – Microfilaments of actin • Enable cells to change shape and move – Intermediate filaments • Reinforce the cell and anchor organelles – Microtubules give the cell rigidity • provide anchors for organelles and act as tracks for organelle movement Overview: Many cell organelles are connected through the endomembrane system – All cells on earth are enclosed in membranes that maintain internal conditions different from the surroundings, have DNA as their genetic material and can convert forms of energy from one to another. – Membranes form the boundaries of many eukaryotic cells • Compartmentalizing the interior of the cell and facilitating a variety of metabolic activities – The nucleus is the cellular control center • Containing the cell’s DNA, which directs cellular activities Chromatin Nucleolus Nucleus Two membranes of nuclear envelope Pore Rough endoplasmic reticulum Figure 4.5 Ribosomes ORGANELLES OF THE ENDOMEMBRANE SYSTEM The nucleus is the cell’s genetic control center – The largest organelle is usually the nucleus • Which is separated from the cytoplasm by the nuclear envelope Inside the nucleus • Chromatin fibers made up of DNA These thin fibers coil up during cell division becoming thicker and visible. They are called now a chromosome Nucleolus makes ribosomes – Ribosomes on the surface of the rough ER • Produce proteins that are secreted, inserted into membranes, or transported in vesicles to other organelles Transport vesicle buds off 4 Ribosome 3 Secretory (glyco-) protein inside transport vesicle Sugar chain 1 2 Glycoprotein Polypeptide Rough ER The endomembrane system is a collection of membranous organelles • That manufactures and distributes cell products\ Smooth endoplasmic reticulum has a variety of functions – Smooth endoplasmic reticulum, or smooth ER • Synthesizes lipids • Processes toxins and drugs in liver cells • Stores and releases calcium ions in muscle cells Smooth ER Rough ER Nuclear envelope Ribosomes Rough ER TEM 45,000 Smooth ER – A typical animal cell • Contains a variety of membranous organelles Smooth endoplasmic reticulum Nucleus Rough endoplasmic reticulum Flagellum Not in most plant cells Lysosome Ribosomes Centriole Peroxisome Microtubule Cytoskeleton Golgi apparatus Plasma membrane Intermediate filament Mitochondrion Microfilament The Golgi apparatus finishes, sorts, and ships cell products – Stacks of membranous sacs receive and modify ER products • Then ship them to other organelles or the cell surface “Receiving” side of Golgi apparatus Golgi apparatus Golgi apparatus New vesicle forming “Shipping” side of Golgi apparatus Figure 4.9 Transport vesicle from the Golgi TEM 130,000 Transport vesicle from ER The endomembrane system – The various organelles of the endomembrane system • Are interconnected structurally and functionally Rough ER Transport vesicle from ER to Golgi Transport vesicle from Golgi to plasma membrane Plasma membrane Nucleus Vacuole Lysosome Smooth ER Nuclear envelope Golgi apparatus Mitochondria gets chemical energy from food – Mitochondria carry out cellular respiration It uses the chemical energy in food to make ATP for cellular work Mitochondrion Outer membrane Inner membrane Cristae Matrix TEM 44,880 Intermembrane space Lysosomes are digestive compartments within a cell – Lysosomes are sacs of enzymes that function in digestion within a cell 1 Rough ER Transport vesicle (containing inactive hydrolytic enzymes) Golgi apparatus Plasma membrane Engulfment of particle Lysosome engulfing damaged organelle 2 “Food” Lysosomes 3 5 Food vacuole 4 Digestion – Lysosomes in white blood cells • Destroy bacteria that have been ingested • lysosomes also help to digest worn out , damaged cell parts, recycle materials within the cell and fuse with food vacuoles to digest nutrients. Lysosome Figure 4.10B TEM 8,500 Nucleus Lysosomes in white blood cells destroy bacteria and lysosomes also can digest other parts of the cell Abnormal lysosomes can cause fatal diseases – Lysosomal storage diseases. These are rare. • Interfere with various cellular functions • Ex: Tay- Sachs, does not break down lipids in nerve cell membranes. Lipids accumulate • Pompe’s disease, lysosomes cannot digest glycogen and it accumulates in muscle and liver cells Peroxisomes • Specialized vesicles that contains enzymes (catalase) that digest hydrogen peroxide H2 O2 • Our cells produce hydrogen peroxide during metabolism and the enzymes in peroxisomes break it down into water and oxygen gas which are harmless to the cell. Plant Cells • Three organelles animals do not have Chloroplasts Cell wall Central vacuole – A typical plant cell has some structures that an animal cell lacks • Such as chloroplasts and a rigid cell wall Nucleus Rough endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum Golgi apparatus Not in animal cells Microtubule Central vacuole Intermediate filament Chloroplast Microfilament Cell wall Mitochondrion Peroxisome Plasma membrane Cytoskeleton ENERGY-CONVERTING ORGANELLES Chloroplasts convert solar energy to chemical energy. This is where PHOTOSYNTHESIS takes place – Chloroplasts, found in plants and some protists Convert solar energy to chemical energy in sugars Chloroplast Inner and outer membranes Granum Intermembrane space TEM 9,750 Stroma Vacuoles function in the general maintenance of the cell – Plant cells contain a large central vacuole, • Which has lysosomal and storage functions Nucleus Chloroplast Colorized TEM 8,700 Central vacuole Central vacuoles in plants Also help increase the size of cells by absorbing water Are mostly water, minerals and nutrients • Store color pigments (that attract insects) • Store waste products and poisons – Some protists have contractile vacuoles • That pump out excess water Contractile vacuoles LM 650 Nucleus Organelles • NAME LOCATION • Cytoskeleton cytoplasm • Cytosol cytoplasm FUNCTION Maintains cell shape facilitates movement and move materials within the cell Protein rich fluid in which organelles and cytoskeleton are immersed • Nucleus Inside nuclear envelope Site of most of cell’s DNA and nucleolus • Nucleolus Inside the nucleus Synthesis of ribosomal RNA ORGANELLES NAME LOCATION FUNCTION • Rough Endoplasmic Reticulum cytoplasm Protein synthesis,Cell metabolism, • Smooth Endoplasmic Reticulum cytoplasm Lipid synthesis, storage of calcium, Detoxification of toxic substances • Ribosomes Rough ER and free in the cytoplasm Protein synthesis • Vesicles move through cytoplasm Transport • Golgi Bodies cytoplasm Processing, sorting, shipping of proteins and lipids • Mitochondria cytoplasm Gets energy from food (makes ATP during aerobic respiration) ORGANELLES NAME • Lysosomes LOCATION FUNCTION cytoplasm Digestion and breaking down of materials (only in animal cells) • Peroxisomes ( including the cell’s own) cytoplasm Sacs of enzymes that break down substances (alcohol, amino acids) into hydrogen peroxide and then the hydrogen peroxide into water and oxygen. • Plasma Membrane all around the cell Controls substances and signals that go in and out of cells. Maintains shape and volume • Cell wall ( plant cells) cytoplasm Keeps water inside and limits water uptake, protects from outside influences, maintains shape. ORGANELLES NAME LOCATION FUNCTION • Central vacuoles center of plant cell water maintenance, stores waste cytoplasm plastids provide nutrients and (plant cells only) • Plastids (plant cells only) • Chloroplast (plant cells only) pigmentation many throughout carry out photosynthesis the cytoplasm contain chlorophyll CELL JUNCTIONS • What are junctions? Protein or cytoplasmic bridges that serve as physical links between cells. • The junctions between cells help integrate cells into tissues and higher levels of functioning. Junctions make cells living units greater than each individual part. • Junctions serve to send and receive signals and materials and to cement itself to other cells and junctions coordinate cell activities. Plant cells Plants are covered by cell walls composed of cellulose fibers. Cell walls have plasmodesmata, these are channels that pass through adjoining cell walls connecting plant cell to plant cell. Animal cells: Junctions • There are different kinds of intracellular junctions between animal cells, integrating each cell into a greater unit. • Tight junctions • Desmosomes or Anchoring juctions: • Gap or Communication junctions: Tight junctions They fuse cell to cell to prevent leakage. Ex: cells of the lining of the intestines keeping the fluid inside. All cells of most tissues are joined this way. The skin and the lining of internal cavities (epithelial). Gap or Communication junctions: Link the cytoplasm of neighboring cells. They are open channels that allow a flow of materials and signals between cells. • Very common in embryos and in heart tissue to allow for the passage of ions to cause contraction Desmosomes or Anchoring juctions: Joins cells in tissues of the skin, heart and other organs such as the bladder subject to stretching. – Tight junctions can bind cells together into leakproof sheets – Anchoring junctions link animal cells into strong tissues – Gap junctions allow substances to flow from cell to cell Tight junctions Anchoring junction Gap junctions Extracellular matrix Space between cells Figure 4.18B Plasma membranes of adjacent cells Cilia and flagella • move when microtubules bend Figure 4.17A LM 600 Colorized SEM 4,100 – Eukaryotic cilia and flagella are locomotor appendages that protrude from some cells Figure 4.17B Clusters of microtubules Drive the whipping action of these organelles . Flagellum Electron micrographs of cross sections: Outer microtubule doublet TEM 206,500 Central microtubules Radial spoke Dynein arms Flagellum TEM 206,500 Plasma membrane Basal body (structurally identical to centriole) Basal body PLASMA MEMBRANE • Function: The cell’s “gate keeper”. Very important. It controls what goes in and out of a cell. Keeps equilibrium between the inside of cells and the outside and promotes homeostasis. Web site to check: http://www.wisc-online.com/objects/index_tj.asp?objid=AP1101 Membranes • http://www.wiley.com/legacy/college/boyer/ 0470003790/animations/membrane_transpo rt/membrane_transport.htm The plasma membrane of the cell is selectively permeable Controlling the flow of substances into or out of the cell TEM 200,000 Outside of cell Cytoplasm PLASMA MEMBRANE STRUCTURE: It is a LIPID BILAYER. Its main component is a PHOSPHOLIPID molecule. • A phospholipid is made up of a hydrophilic head (water loving) and two hydrophobic fatty acid tails (dislike water). These are arranged in two layers with the fatty acids tails sandwiched between the hydrophilic heads. • The membrane is “fluid”, it moves about, tails twist and wave • Embedded in the phospholipid bilayer are the surface proteins. • The membrane is “a mosaic” of different proteins embedded in the fluid matrix of the lipid bilayer. What makes up the plasma membrane? – Phospholipids are the main structural components of membranes Membrane phospholipids form a bilayer • Have a hydrophilic head and two hydrophobic tails Hydrophilic head Phosphate group CH2 O C O CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 O + CH3 CH2 N CH3 CH3 CH2 O P O– O CH2 CH O C O CH2 CH2 CH2 CH2 CH2 CH2 Symbol CH2 CH CH CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3 Hydrophobic tails Phospholipids form a two-layer sheet Called a phospholipid bilayer, with the heads facing outward and the tails facing inward Water Hydrophilic heads Hydrophobic tails Water How does it work? • Membrane is selectively permeable or semipermeable. Small molecules that are electrically neutral diffuse easily in and out such as O2, CO2, and alcohols. • The non-polar phospholipid tails of the bilayer repel charged molecules but allow lipid soluble molecules to pass easily. • Sugars need to be transported through a channel as well as charged ions such as H+, Na+, K+, Cl • Large molecules (like proteins) cannot diffuse through and must enter the cell by other mechanisms such as active transport. Active transport uses energy (ATP) to “push” the molecules in and out. • Serious diseases associated with cell membrane defects: Multiple Sclerosis, there is a myelin cover on axons of nerve cells. Because it is defective muscle control is lost Cystic Fibrosis, The channels for chloride to pass through the membrane do not work. Chloride ion are not able to leave the cell. Results in thick mucus in respiratory track and other ducts in the body. Proteins found in the plasma membrane: • Integral penetrate the hydrophobic core of the lipid bilayer • Peripheral are loosely bound to the surface of the membrane • • • • Transport proteins Receptor proteins Recognition proteins Adhesion proteins Proteins found in the plasma membrane: • Transport proteins: These are open on both sides making a channel, a passage. Water soluble substances pass through it. It is very specific for the substance that it moves. • Receptor proteins: Grab or bind substances to pass them through. Have a binding site with a specific shape that fits the shape of another molecule. It can bind a chemical messenger such as a hormone which then causes a change in the shape of the protein that relays the message to the inside of the cell. • Recognition proteins: These are glycoproteins. Have a short chain of sugars attached to it. Are like fingerprints. Serve as identification tags that are recognized by other cells. Your cells recognize “your own” • Adhesion proteins: Like “glue”, make cells stick together. The membrane is a fluid mosaic of phospholipids with proteins and other molecules embedded in a phospholipid bilayer Fibers of the extracellular matrix Carbohydrate (of glycoprotein) Glycoprotein Glycolipid Plasma membrane Phospholipid Proteins Microfilaments of cytoskeleton Cholesterol Cytoplasm Membrane proteins also function in transport Moving substances across the membrane ATP Other membrane proteins Function as receptors for chemical messages from other cells Messenger molecule Receptor Activated molecule Many membrane proteins Function as enzymes