Cell Structure and Function Biology 12 Unit 1 Cell Structure and Function Inquiry into Life pages 45 59 and 68-69
Assignments for this Unit Pick up the notes/worksheet for this unit and the project There will be test at the end of the unit composed of 3 parts: Matching keyterms Multiple Choice Labelling Diagrams
Cell Structure
Cell Theory Cells are the functional unit of life They comprise the smallest living unit of any organism All cells come from pre-existing cells Cells have a complex structure and many specialized organelles These organelles often work inter-relatedly
The Nucleus can be observed as the large, centrally located control centre of the cell surrounded by a double layered membrane with pores contains DNA deoxyribonucleic acid transcription and replication of DNA occurs here
The Nucleus Nuclear Membrane
The Nucleus The nuclear membrane (nuclear envelope) is what separates the nuclear material from the rest of the cytoplasm It consists of a double membrane with pores
The Nucleus Nuclear Membrane Nuclear Pore
The Nucleus Nuclear pores are channels that allow the passage of protein molecules into the nucleus and ribosomal subunits out of the nucleus The pores are ~ 100 nm in diameter, or about 1/10 000 000 metres
The Nucleus Nuclear Membrane Nucleolus Nuclear Pore
The Nucleus The nucleolus is the most prominent structure in the nucleus, seen as a dark, spherical mass The nucleolus produces ribosomal RNA (ribonucleic acid) = rrna rrna joins with proteins to form the subunits of ribosomes
The Nucleus Nuclear Membrane Nucleolus Nuclear Pore Chromatin
The Nucleus Chromatin is DNA and associated proteins in their uncoiled state During interphase, chromosomes are unwound and and cannot be distinguished individually The chromatin is immersed in a semifluid medium called nucleoplasm, which is like cytoplasm in the nucleus
The Nucleus This is an electron micrograph of a liver cell nucleus Notice: nuclear membrane nucleolus chromatin nucleoplasm nuclear pores?
Ribosomes Ribosomes are small granules that appear dark in micrographs They are involved in protein synthesis forming chains of amino acids to make long protein molecules Found on the endoplasmic reticulum and free floating in the cytoplasm
Ribosomes Cytoplasmic ribosomes are often found in small clusters called polyribosomes or polysomes These produce proteins that are used inside the cell
Ribosomes Most ribosomes are found attached to the surface of the endoplasmic reticulum (ER) These produce proteins to be transported outside the cell through the ER
Endoplasmic Reticulum A series of membranous channels and flattened vesicles that are physically connected to the nuclear membrane The ER works with other organelles to restrict chemical reactions to particular areas
Endoplasmic Reticulum Rough endoplasmic reticulum (rough ER) is superficially covered in ribosomes These ribosomes synthesize proteins that enter the ER
Endoplasmic Reticulum
Endoplasmic Reticulum Glycoproteins can be found on the extracellular side of the cell membrane Proteins in the ER undergo modification, often forming a glycoprotein (protein with an attached carbohydrate molecule)
Endoplasmic Reticulum The proteins are then transported to the Golgi apparatus after processing
Endoplasmic Reticulum Smooth ER is a different form where there are no ribosomes on the surface Smooth ER is continuous with rough ER Different functions depend on the type of cell they are in synthesize phospholipids that are on the surface of the cell membrane testosterone production in testes detoxifying in the liver
Endoplasmic Reticulum Smooth ER always forms vesicles to transport proteins to the Golgi apparatus
Vesicles Vesicles are membranous sacs used to transport compounds around the cell often formed from the Golgi apparatus or from the infolding of the cell membrane
Vesicles
Golgi Apparatus Also known as Golgi bodies Appear as a series of flattened pancakes (saccules)
Golgi Apparatus Functions to process, package, and secrete Further processes proteins These proteins are packaged into vesicles The vesicles are are formed from the Golgi apparatus membrane where they will secrete their contents from the cell membrane --> exocytosis
Vesicle Secretion
Lysosomes Lysosomes are membrane-bound vesicles of digestive enzymes produced by the Golgi appartus Essentially suicide sacs Functions: attach to food vacuoles to digest contents destroys old or malfunctioning organelles
Lysosome
Vesicle Budding and Secretion http://www.sumanasinc.com/webcontent/animati ons/content/vesiclebudding.html
Mitochondria Singular is mitochondrion Site of cellular respiration glucose + oxygen --> carbon dioxide + water + ATP (energy) C 6 H 12 O 6 + 6 O 2 --> 6 CO 2 + 6 H 2 O + ATP (energy) Cells use ATP (adensine triphosphate) for energy The more active the cell, the more energy it requires, the more mitochondria they have eg. muscle cells
Mitochondria
Mitochondria Bound by a double membrane Inner membrane invaginates (folds in) forming cristae, creating a high surface area for chemical reactions Inner filled spaced called the matrix, containing its own DNA, ribosomes, enzymes
Chloroplasts Chloroplasts are the site of glucose production in autotrophs through a process called photosynthesis They convert solar energy into chemical energy solar energy carbon dioxide + water -----> glucose + oxygen solar energy 6 CO 2 + 6 H 2 O -----> C 6 H 12 O 6 + 6 O 2
Chloroplasts Chloroplasts have a double membrane The inner fluid-filled space is called the stroma Within the stroma are interconnected sacs called thylakoids Thylakoids can be stacked to form grana (sing. granum)
Chloroplasts
Chloroplasts Chlorophyll is a green pigment found within the thylakoid membranes in grana Photosynthesis takes place specifically within the grana in chloroplasts Also in the stroma is DNA, ribosomes, and enzymes, just like in the matrix of mitochondria!
Vacuoles Membrane bound sac filled with water and/or chemicals Used in animal cells for the digestion of food and the elimination of excess water through exocytosis Used in plant cells for storage of metabolic wastes and pressurizing the cell
Cell Organelles Video http://www.teachersdomain.org/resource/tdc02.sc i.life.cell.organelles/
Cell Membrane Also known as the plasma membrane Separates the internal environment (intracellular) with the external environment (extracellular) Composed of a phospholipid bilayer with various partially and wholly embedded proteins
Cell Membrane
Cell Membrane The description of the membrane is called the Fluid Mosaic Model It has a fluid consistency, like vegetable oil Proteins are scattered within the membrane and on the intracellular surface
Cell Membrane
Cell Membrane The phospholipid molecule is polar two different parts The phosphate head is hydrophilic (water loving) The lipid tail is hydrophobic (water fearing)
Cell Membrane Embedded within the lipid tails are cholesterol molecules which adds strength and stiffness to the membrane Integral proteins are those that are embedded in the phospholipid bilayer Peripheral proteins are those that occur on one side of the bilayer or the other Glycoproteins are only on the extracellular side of the membrane
The semifluid medium between the cell membrane and the nucleus that contains organelles Cytoplasm
Cell Membrane, Nucleus and Cytoplasm Video http://www.teachersdomain.org/resource/tdc02.sc i.life.cell.nucleus/
Cell Wall Found only in plant cells two types It is a permeable, rigid structure that adds support and protection Primary cell walls are composed of cellulose molecules Secondary cell walls are composed of lignin, an even stronger molecule
Cell Wall (primary) copyright Dennis Kunkel. All rights reserved.
Cell Wall (primary)
Cytoskeleton Composed of a network of interconnected filaments and tubules Maintains cell shape and structure, causes cells and organelles to move Can be assembled and disassembled very rapidly Three components: actin filaments microtubules intermediate filaments
Cytoskeleton
Cytoskeleton
Cytoskeleton actin filaments intermediate filaments microtubules
Cytoskeleton Tutorial http://www.wiley.com/college/pratt/0471393878 /student/animations/actin_myosin/index.html
Flagella and Cilia Flagella and cilia are structures composed of microtubules and are used for locomotion http://programs.northlandcollege.edu/biology/b iology1111/animations/flagellum.html
Summary Organelles are membrane bound structures with varied and dedicated functions Some organelles work together, forming a network to move materials throughout the cell rough ER and smooth ER Golgi apparatus vesicles cell membrane
Summary Mitochondria and chloroplasts are double-membrane bound energy-related organelles Photosynthesis occurs in the grana of chloroplasts Cellular respiration occurs in the matrix of mitochondria Probable independent origin due to the presence of extranuclear DNA
Summary All cells maintain their structure using a dynamic cytoskeleton composed of three types of elements Plant cells have additional means of support a permeable cell wall and a large central vacuole that maintains turgidity