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Transcript
th 7 Grade Science Unit 2NCFE Review Cells • The basic units of a living system or organism 2 Types of Cells: • Prokaryotic - Cells that don’t have a membrane-covered nucleus for example: bacteria • Eukaryotic – Cells with a nucleus covered by a membrane for example: plant and animal cells How do we know cells exist? • Invention of the microscope made it possible for people to discover and learn about cells • Robert Hooke looked at cork cells • Anton van Leuenhock used a simple microscope and was the first person to see microorganisms. Anton van Leeuwenhoek • First compound light microscope Cell Theory – • developed by 3 German scientists: • Matthias Schleiden, • Theodor Schwann, • and Rudolf Virchow These scientists discoveries led to the cell theory… What is the CELL THEORY??? Theory that states… 1. All organisms are made of one or more cells. 2. The cell is the basic unit of life which can perform life processes. 3. All cells come from other living cells. Cells • Smallest living unit • Most are microscopic Characteristics of All Cells • • • • A surrounding membrane Protoplasm – cell contents in thick fluid Organelles – structures for cell function Control center with DNA Organelles • -Tiny cell structures that are specialized parts of a cell that have specific functions – a cell “organ.” Representative Animal Cell Animal Cell Representative Plant Cell Plant Cell CELL MEMBRANE • – “gate keeper” • outer boundary (or layer) of the cell • controls the movement of materials into and out of the cell CELL WALL • found in plant cells • tough rigid boundary – made of cellulose • gives cells their shape (it also provides protection, as well as support) CYTOPLASM • – “cell fluid” • a gel-like material inside the cell • Many cellular activities occur here and where the organelles are contained NUCLEUS – “brain of the cell” • controls cell processes • Contains DNA or chromosomes - the heredity material or genetic blueprint of the cell NUCLEAR MEMBRANE • – materials pass in and out through tiny holes called porins NUCLEOLUS • – ribosomes are made here Cell Structures and Functions Chloroplast Traps suns energy and Makes food Location: in plant cells Cell Parts and Functions Mitochondria Makes energy/ powerhouse Location: in cytoplasm RIBOSOMES • – “protein factories” • place where protein is made in the cells • some are attached – some float in the cytoplasm ENDOPLASMIC RETICULUM • – “conveyer belt” • transports synthesized proteins throughout the cell GOLGI BODIES (Also called the Golgi Apparatus) • sort, modify, process, and ship the proteins through the cell • (Also known As GOLGI Apparatus) VACUOLES “storage” • store water, sugar, salts, nutrients, & wastes in cells • maintains the proper pressure to provide structure and support in plant cells • – LYSOSOMES • contain chemicals that break down waste materials. What is cellular respiration? ð The process by which cells break down simple food molecules (glucose) to release energy. Glucose What is selectively permeable? ¤ A property of cell membranes to allow some substances through, while other cannot A spaghetti strainer allows water to pass through but does not allow spaghetti to pass What two ways do materials enter the cell? ¤ Passive Transport ¤ Active Transport Entering through the Cell Membrane Passive Transport Diffusion/ Osmosis Active Transport What is passive transport? ¤ The movement of materials through the cell membrane without using energy ¤ Diffusion and Osmosis What is diffusion? NO ENERGY! ¤ The process by which molecules tend to move from an area of high concentration to an area of low concentration. diffusion What is active transport? ¤ The movement of materials through a cell membrane using energy ¤ Uses energy to move molecules from an area of low concentration to an area of high concentration. ENERGY! Unicellular organisms • Some organisms only consist of a single cell • But these do usually have the components of cells (nucleus, membrane etc) Image Credit Paramecium Euglena • Environment: Ponds or puddles with rich organic matter. • Movement: By flagella – Flagellum: helps to move – Chloroplast: helps with photosynthesis • Food: They make their own food or absorb food from their environment. Euglena Amoeba • Environment: Mud at the bottom of freshwater ponds. • Movement: They change shapes which allows them to move (called shape shifters). Pseudopodium: what allows it to move over mud (false foot) • Capturing Prey: They surround their prey and engulf it. Amoeba Volvox • Environment: ponds, ditches, shallow puddles • Movement: They beat cillia which allows it to swim. – Daughter colonies – Cillia: helps to move – Chloroplast: contains chlorophyll • Food: makes its own food by photosynthesis. Volvox Paramecium • Environment: Fresh water or stagnant water • Movement: Cilia bend and straighten helping propel the paramecium through water – Cilia: hair-like projections that propel it through water • Food: uses cilia to sweep the food into the cell. Paramecium Where are my “genes”? • Your genes are inside all • the cells of your body. • Inside the nucleus of your • cells, are chromosomes. • Chromosomes are made • of tightly wound up DNA • (called chromatin). • The DNA code makes up • your genes. Chromosomes?!?! • Chromosomes are tightly wound-up “packages” of DNA. • Humans have 23 pairs of chromosomes, 46 in all. • (Sperm & Egg cells only • have 23 single chromosomes!) • Each parent contributes one chromosome to each pair, so you get half your chromosomes from your mom and half from your dad. The Structure of DNA • DNA looks like a long, twisted ladder called a DOUBLE HELIX. • There are 2 long strands. • These are the sugarphosphate • “backbones” of DNA. • The “steps” of the ladder that • connect the strands are base• pairs. DNA • DNA is located in the nucleus and controls all cell ac+vi+es including cell division • Long and thread-‐like DNA in a non-‐dividing cell is called chroma+n • Doubled, coiled, short DNA in a dividing cell is called chromosome Consists of 2 parts: chroma+d and centromere Asexual vs. Sexual Reproduction 47 Asexual Reproduction • Requires only one parent • Offspring have 100% the same chromosomes as the parent. – In other words, the offspring are exact “clones” of the parent. – Most unicellular organisms reproduce this way. – Mitosis 48 Different Types of Asexual Reproduction • Fission • Budding (Like when a plant has a new shoot that can be cut off and planted, which becomes a new plant.) • Fragmentation (Like when an organism is cut in 2 and becomes 2 different organisms) • Regeneration (Like when a starfish growing an arm back) Cell Division—Mitosis Notes Cell Division — process by which a cell divides into 2 new cells • Why do cells need to divide? 1. Living things grow by producing more cells, NOT because each cell increases in size 2. Repair of damaged Hssue 3. If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell • The original cell is called the parent cell; 2 new cells are called daughter cells • Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of gene+c informa+on from parent cell • Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell 2 Daughte r Cells Parent Cell • Many organisms, especially unicellular organisms, reproduce by means of cell division – called asexual reproduc+on – Ex: bacteria o 2 idenHcal “sister” chromaHds aVached at an area in the middle called a centromere o When cells divide, “sister” chroma+ds separate and 1 goes to each new cell • ChromaHn to chromosomes illustraHon: ChromaHn Duplicates itself Why does DNA need to change from chromaHn to chromosome? Coils up into chromosomes More efficient division Cell Cycle -‐-‐ series of events cells go through as they grow and divide • Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again • 4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT) Prophase Metaphase—(Middle) Anaphase—(Apart) Anaphase—(Apart) Telophase—(Two) Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) aZer the nucleus divides In animal cells the cytoplasm pinches in In plant cells a cell plate forms • AZer mitosis and cytokinesis, the cell returns to Interphase to conHnue to grow and perform regular cell acHviHes Phase Interphase Prophase Chromosome Appearance & Loca+on DNA copies itself; chromatin Chromosomes coil up Important Events DNA replication, cell grows and replicates organelles Nuclear envelope disappears, spindle fibers form Chromosomes line up in the middle Spindle fibers connect to chromosomes Anaphase Chromosome copies divide and move apart Telophase Chromosomes uncoil back into chromatin Cytokinesis Chromati n Spindle fibers pull chromosome copies apart to opposite poles Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers Division of the rest of disappear the cell: cytoplasm and organelles Metaphase