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Transcript
1.2 – Cells: The Basic Units of Life There are many different kinds of cells designed to carry out different functions The most common division of cell types is into the categories: ANIMAL and PLANT. General Structure of a Cell Extracellular fluid (ECF) – The watery environment outside of a cell Cytosol – The aqueous solution inside a cell in which all organelles are suspended Cytoplasm – the cytosol and cell organelles outside of the nucleus • The nucleus acts as the control center of the cell Cell membrane (CM) – separates the insides of the cell from the extracellular fluid • Controls the movement of substances into and out of the cell • Has a property known as permeability – most cells are ‘semi-permeable’ (meaning they selectively allow certain substances through) Cell wall – firm, porous structures found outside of the cell membrane which give plants rigidity while allowing water and dissolved materials to pass through; found ONLY in PLANTS Membranes Made of a phospholipid bilayer – 2 layers of fat molecules that have phosphate groups attached to them Also have proteins and carbohydrates Are “fluid” – always moving Organelles such as the nucleus, mitochondria, and chloroplasts also have membranes Nucleus The control center of the cell that directs all of the cell’s activities Contains the genetic material DNA and RNA Nucleolus – produces ribosomes Nuclear envelope – porous membrane that surrounds the nucleus and separates the nucleus from the cytoplasm Nuclear Pore – opening that allows things to pass into and out of the nucleus Nucleoplasm – the fluid inside the nucleus Ribosomes Produce proteins Found in the cytoplasm or attached to membranes • Cytoplasm ribosomes – make proteins that are used inside the cell • Membrane ribosomes – make proteins that are used outside the cell Endoplasmic Reticulum (ER) Membranous tubes that connect to the nuclear envelope There are 2 types of ER: 1. Rough Endoplasmic Reticulum (RER) • Has ribosomes attached to it • Many proteins are made on it 2. Smooth Endoplasmic Reticulum (SER) • Doesn’t have ribosomes • Used for detox • Produces molecules of fat The products of the ER are packed in membrane-bound structures called vesicles Vesicles can be formed by the ER or the Golgi apparatus • Used for transport Golgi Apparatus (GA) The “post office” of the cell Membranous tubes Produce lysosomes Chemically changes the proteins and fats made in the ER and packages them into vesicles The vesicles move through the cytoplasm, attach to the CM, and release their contents into the ECF Lysosomes ONLY in ANIMAL cells Contain proteins that can break down the molecules that cells are made of into their individual chemical components(breaks big compounds into individual chemical components) • Used to digest food particles, can destroy invading organisms (ie. Bacteria, viruses) • Also used to decompose entire cells when cells get too old to function properly Apoptosis – cell suicide The cell uses the remaining compounds to build new cells Mitochondria The “powerhouse” of the cell Membranous organelles that float freely in the cytoplasm Location of cellular respiration (CR) – a set of reactions occurring in the mitochondria (in both plants and animals) that produces energy (ATP) Has 2 membranes: 1. Outer membrane – smooth 2. Inner membrane – highly folded; folds are called cristae • Cristae folds contain the compounds that carry out the cellular respiration reactions • The folds increase the surface area of the membrane so that the mitochondria can produce a lot of energy • Cells that require a lot of energy have A LOT of mitochondira (e.g., muscle cells, nerve cells) Matrix – the protien-rich fluids that fill the space inside of the mitochondria (inside the inner membrane) Intermembrane space – space between the outer and inner membranes Centrioles Produce spider-web like fibres called spindle fibres which are used in cell replication/division (more on these later on in the course ) Plastids Store useful materials and carries out vital functions such as photosynthesis • Photosynthesis – a set of chemical reactions that converts carbon dioxide (CO2) and water (H2O) into oxygen (O2) and food molecules (glucose) Chloroplast – a plastid that contains chlorophyll and carries out the reactions of photosynthesis • Contain 2 membranes: outer and inner • Thylakoids – membrane-bound compartment found in chloroplasts • Granum – stack of thylakoids found in chloroplasts • Chlorophyll – the green pigment that begins the process of photosynthesis; it is found in the thylakoid membranes • Stroma – protein-rich fluid that fills the space between thylakoid membranes and the inner membrane of the chloroplast Other plastids include: • Amyloplasts – white/colourless; store energyrich products of photosynthesis in the form of starch • Chromoplasts – colourful; contain the red, orange, yellow pigments found in flowers, fruits, and vegetables Vacuoles Large membrane-bound sacs filled with a watery solution (water, dissolved sugars, minerals, and proteins) Turgor pressure – pressure, caused by water in the cytoplasm and 1 or 2 large vacuoles, that helps keep the cell membrane pressed firmly against the cell wall of a plant cell • This is why vegetables are firm and watery When plant cells lose water, the vacuoles shrink, turgor pressure decreases, the plant structures wilt Homework • Page 15 # 2-7, 9