competency*4*review** - rankin county school … 4...sides,*aach*to*spindle*fibers* ... •...
TRANSCRIPT
Cells
The Cell Theory • All living things are made of one or more CELLS.
• Cells are the basic unit of structure and func@on in an organism.
• New cells are produced from exis@ng cells.
2 types of cells
• Prokaryotes – Cells without a nucleus or organelles surrounded by membranes
• Eukaryotes – Cells with a nucleus and organelles surrounded by membranes.
Prokaryotes
• Single celled organism • Has DNA that is circular floa@ng all around in the cytoplasm
• Only has ribosomes and no other membrane bound organelles
• Most common = bacteria – Some can make their own food, most get food from other sources
Eukaryotes • There can be singled celled eukaryotes as well as mul@cellular
• Highly organized • More complex than prokaryotes
Cell membrane (plasma membrane)
• Made mainly of phospholipids (2 layers) and proteins
Outside of cell
Inside of cell (cytoplasm)
Cell membrane
Proteins
Protein channel Lipid bilayer
Carbohydrate chains
Cell membrane made of:
• Phospholipids have hydrophobic tails made of lipids and hydrophilic heads.
3 kinds of proteins-‐ • channel-‐provides a path for materials to move in and out
• marker-‐ used for recogni@on
• receptor-‐ receive signals
Cell membrane
• Acts as a boundary • Controls what enters and leaves cell • Fluid (fluid mosaic model)
– Molecules in cell membranes are constantly moving and changing (ex. cholesterol and carbohydrates)
Nucleus
• LARGEST organelle in animal cells • Surrounded by nuclear envelope • Contains nuclear pores = openings that allow molecules to move in and out of nucleus
• Contains gene@c material (DNA) • Control center of the cell
Cytoskeleton
• Helps cell maintain shape • Help move organelles around • Made of proteins
– Microfilaments – Microtubules
Centrioles
• Made of microtubules • Only seen in animal cells during cell division • Func@on: Guide chromosomes during PMAT
Mitochondria
• “Powerplant of cell” • Site of cellular respira@on • Burns glucose to release energy • Stores energy as ATP • Surrounded by double membrane
– Inner membrane = cristae
Ribosomes
• Can be free in cytoplasm or a[ached to rough ER
• Made of rRNA • Func@on: assembles proteins • Called the site of protein synthesis
Endoplasmic re@culum (internal network of membranes)
• Rough ER – A[ached ribosomes make proteins which are modified and transported to Golgi for export
• Smooth ER – Makes membrane lipids (steroids)
– Regulates calcium in muscles
– Breaks down toxins in liver
Golgi Apparatus
• Looks like a “stack of pancakes” • Made of membranes • Modify, sort, and package substances from ER for storage or export out of cell
Lysosomes
• Sac containing diges@ve enzymes
• Digests food molecules and unwanted cells/cell parts
• Plays a role in apoptosis “programed cell death” – Cell suicide for the good of the organism
Movement • Pseudopodia = “false feet” help amoebas with movement and ea@ng (phagocytosis) • Cilia = many and short microtubules (li[le hairs)
– Move cells – Move substances past cells
• Flagella = few and long microtubules (like a tail)
– Move cells
What’s special about plant cells?
• Cell wall • HUGE central vacuole • Chloroplasts • No centrioles!!
Cell wall
• Found outside the cell membrane • Provides support and protec@on • Made of Cellulose (carbohydrate) makes plant sturdy
• Bacteria have cell walls made of pep@doglycan instead
• Cell walls of fungi are made of chi@n
Vacuoles
• Storage space for: proteins, carbohydrates, water, waste
• Contrac@le vacuoles control excess water in a paramecium (homeostasis)
• Huge in plant cells, small animal cells, not in bacteria
Chloroplast
• Surrounded by double membrane • Thylakoids = membrane sacs inside • Contains chlorophyll where photosynthesis happens
• Found in photosynthe@c cells (plants, some bacteria and protozoans)
Molecule Movement and Cells
• Passive Transport = does not require energy by the cell
• Ac@ve transport = requires energy!
Passive transport
• No energy required • Move due to gradient
– Differences in concentra@on, pressure, charge • Move to equalize gradient (equilibrium)
– High concentra@on moves toward low concentra@on
• 3 Types – Diffusion, osmosis, facilitated diffusion
Osmosis
• Special form of diffusion • Fluid flows from lower solute concentra@on • Always involves movement of water
– Into cell – Out of cell • Water will move From High to Low
Facilitated Diffusion
• Channels (are specific) help molecule or ions enter or leave the cell
• Channels usually are transport proteins
Ac@ve transport
• Molecular movement • Requires energy (against gradient) • Example: sodium-‐potassium pump
Endocytosis-‐the taking in of material
• Phagocytosis – cell ea@ng(large material)
• Pinocytosis – cell drinking (small material)
Cellular reproduc@on
• 5 ways – 1. Fission – 2. Budding – 3. Vegeta@ve propaga@on – 4. Mitosis – 5. Meiosis
Binary Fission
• Prokaryotes (bacteria) • Asexual reproduc@on • Cell makes copy of DNA and grows in size • Membrane will divide and two new cells formed
Vegeta@ve propaga@on
• Asexual reproduc@on in plants • Runners will grow off from the parent plant and root to form a new iden@cal plant.
Cell cycle • G1 phase – periods of cell
growth • S phase – DNA
synthesized • G2 phase – organelles
produced and get ready to divide
• M phase (mitosis) – division of cell nucleus
• Cytokinesis –division of the cell cytoplasm
Interphase
• Not part of mitosis • “normal cell life” • Cell division does NOT occur • Chroma@ds copy themselves during S phase • Covers G1, S, and G2
Mitosis
• Division of cell nucleus • Creates daughter cells that are IDENTICAL to the original cell
• Have the en@re set of chromosomes exis@ng in pairs – diploid
Mitosis • Prophase – chroma@d coils to
form chromosomes, nuclear membrane dissolves, centrioles migrate to opposite sides, a[ach to spindle fibers
• Metaphase – chromosome pairs line up at the equator
• Anaphase – chromosome pairs separate and are pulled apart by the spindle fibers
• Telophase – chromosomes uncoil, spindle fibers dissolve, nuclear membrane reforms
• Cytokinesis – Division of the cytoplasm to make two new cells
Uncontrolled cell growth
• Cancer – do not respond to signals that regulate growth of most cells.
• Form masses called tumors
Meiosis
• A form of cell division by which gametes, with half the number of chromosomes, are produced.
• Diploid (2n) à haploid (n) • Sexual reproduc@on • Two divisions (meiosis I and meiosis II)
Interphase I
• Similar to mitosis interphase • DNA replicates in the S phase • Each duplicated chromosome consist of two iden@cal sister chroma@ds a[ached at their centromeres.
• Centriole pairs also replicate.
Meiosis 1 – spliing homologous chromosomes
• Cell division that reduces the chromosome number by one-‐half
• Prophase 1 – longest and most complex, chromosomes form, homologous chromosomes come together to form a tetrad. Crossing Over occurs here!
• Metaphase 1 – tetrads align on the equator • Anaphase 1 – homologous chromosomes separate and go to opposite ends of the cell
• Telophase 1 – a nuclear membrane will form around each chromosome set
• Cytokinesis occurs and two cells are formed.
Crossing over
• Crossing over may occur between homologous pairs.
• Segments of nonsister chroma@ds break off and rea[ach to the other chroma@d
• Causes gene@c varia@on • Happens in Prophase 1
Nonsister chroma@ds Tetrad
Meiosis II – spliing sister chroma@ds
• No interphase II or very short, no DNA replica@on, very similar to mitosis
• Prophase II – nucleus disappears, chromosomes condense, spindle forms
• Metaphase II – chromosomes (not homologous) line up at equator
• Anaphase II – sister chroma@ds separate • Telophase II – nucleus reforms, spindle disappears
• Cytokinesis occurs
Levels of organiza@on • Cells
– Basic unit of structure and func@on in the human body. – Ex: nerve cells, blood cells, bone cells
• Tissues – Group of cells that work together to perform the same func@on
• Organs – A group of two or more different types of @ssue that work together to perform a specific func@on
– Ex: heart (made of muscle and connec@ve @ssue) • Systems
– Group of two or more organs that work together to perform a specific func@on.
– Ex: circulatory, diges@ve, nervous, etc. • Organism
Plants are either vascular or nonvascular
• Vascular plants form @ssues called xylem and phloem – Xylem carries water throughout the plant – Phloem carries nutrients and food throughout the plant
• Nonvascular plants DO NOT have xylem or phloem or true roots, stems, or leaves. – Small because no way of transpor@ng water around the plant.
Plant adapta@ons
• Protec@on – thorns, bad taste, poison, spikes • Obtaining food – larger the leaves, the more sun they can capture
• Seeds – they are formed when the pollen fer@lizes the egg. Fruit protects seed.