Cell Structure & Interactions

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2 Cells Structures & Interactions Overview 1830s-Botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory All living things are composed of one or more cells The cell is the basic unit of life All new cells arise from existing cells

3 Cells Structures & Interactions Overview Cells are made from organic compounds (as discussed last week) Must have carbon and hydrogen in their structure Organized as relatively simple or more complex molecules Four types of Organic Compounds Carbohydrates ( Sugars ) Lipids ( Fats ) Proteins Nucleic Acids (DNA and RNA)

4 Cells Structures & Interactions Overview Cells move organic and inorganic compounds into and out of the cell across the cell membrane in order to maintain homeostasis Specialized physical connections Passive transport processes Active transport processes

5 Cell Structure

6 Cell Structure All animal & plant cells are eukaryotic Contain smaller membrane-bound structures inside the cell Prokaryotic cells lack membrane bound structures Bacteria, for example

7 Parts of Prokaryotic Cells Capsule Polysaccharides Cell Wall Rigid, contains proteins, lipids Cell (plasma) Membrane Pili Cytoplasm Ribosomes DNA Nucleoid area

8 Parts of Eukaryotic Animal Cells Cell (Plasma) Membrane Phospholipid bilayer Embedded proteins, carbohydrates, etc Functions to Maintain cell boundries Helps provide shape Controls movement in/out of the cell Confines the cytoplasm

9 Parts of Eukaryotic Animal Cells Cilia Small motile extension of the cell membrane Contain microtubules Usually numerous Keep cell surface clear and help move the cell Flagella Large motile extension of the cell membrane Usually single Helps move the cell Pseudopodia Cytoplasmic streaming causes the cell membrane to extend outward Helps move the cell

10 Parts of Eukaryotic Animal Cells Nucleus Nuclear Envelope Phospholipid bilayer Contains nucleopores DNA Chromatin = DNA wrapped around proteins Number varies with the type of animal Chromosomes Highly condensed chromatin Nucleolus (pleural, nucleoli) Areas of DNA in the nucleus where RNA is being made Function to store & process genetic information (discussed later)

11 Parts of Eukaryotic Animal Cells Endoplasmic Reticulum Phospholipid membrane Continuation of the nuclear envelop Smooth ER lacks ribosomes Indicates proteins are being produce for use by the cell Rough ER contains surface ribosomes Area of the ER where proteins are produced for transport out of the cell

12 Parts of Eukaryotic Animal Cells Ribosomes RNA + proteins Site of protein synthesis Golgi bodies Stacks of flattened phospholipid membranes Warehouse for proteins Sort, modifies and repackage proteins from the ER for export out of the cell

13 Parts of Eukaryotic Animal Cells Mitochondria Double membrane organelle (phospholipid) Inner membrane is very folded Self-replicating Contains its own DNA for the synthesis of its own proteins Site of energy production for the animal cell

14 Parts of Eukaryotic Animal Cells Vesicles Membrane-bound sacs with various cell functions Lysosomes Contain digestive enzymes janitors of the cell Food vacuole Store food sources Contractile vacuole Removes water from the cell

15 Parts of Eukaryotic Animal Cells Cytoskeleton Near invisible network of small proteins called microfilaments and microtubules Support & maintain cell shape Support movements within the cell Centrioles Microtubules arranged in a cylinder Important to cell replication Centrosome

16 Animal Cells vs Plant Cells Animal Cells Centrioles Centrosomes Lysosomes Plant Cells Cell wall Chloroplasts Plamodesmata Plastids

17 Cell Interactions

18 Cell Interactions Overview To grow, repair themselves, and reproduce cells require two things; building materials and energy Building materials and energy are derived from organic and inorganic compounds in the environment Therefore, cells MUST have mechanisms to moving these organic and inorganic compounds into and out of the cell These mechanisms allows cells to interact with each other and the environment

19 Mechanisms for Cell Interactions Specialized physical connections between cells Passive transport processes across the cell membrane Active transport processes across the cell membrane

20 Specialized Physical Connections Tight junctions Adhesion junctions Communicating junctions Common among animal cells that are tightly packed together

21 Membrane Permeability Permeability = what get through the membrane Fully permeable = everything gets through Non-permeable = nothing gets through Cell Membranes are Selectively permeable Variably permeable to organic & inorganic molecules Fully permeable to water

22 Transport Processes Cells exist in a watery solution and contain watery solutions Solutions Solvent = water Solute = organic and inorganic compounds The selectively permeable nature of cell membranes dictates how parts of solutions can be transported across the membrane

23 Passive Transport Processes Random movement of particles from an area of high concentration to an area of low concentration Energy for this movement is derived from the internal energy of the particles moving Examples of Passive Transport Simple Diffusion Facilitated Diffusion Osmosis

24 Passive Transport Processes Simple Diffusion Random movement of particles from an area of higher concentration to an area of lower concentration Energy to move comes from the particles themselves

25 Passive Transport Processes Facilitated Diffusion Movement of particles across a cell membrane from an area of higher concentration to an area of lower concentration Requires a protein carrier Energy comes from the particles themselves

26 Passive Transport Processes Osmosis Net diffusion of water across a cell membrane from an area of higher concentration to an area of lower concentration Membrane must be water permeable Energy comes from the water molecules themselves

27 Active Transport Processes Movement of particles across the cell membrane from an area of lower concentration to an area of higher concentration Requires Energy Protein carriers Examples of Active Transport Sodium-Potassium Pump Endocytosis Phagocytosis Pinocytosis Receptor-mediated endocytosis Exocytosis

28 Active Transport Processes Sodium-Potassium Pump Active transport of sodium and potassium across the cell membrane against their concentration gradients As much as 40% of the energy used by an animal's cell is used to operate this pump

29 Active Transport Processes Endocytosis Ingestion of materials by the cell Requires energy Phagocytosis Cell eating Plasma membrane forms a pocket that engulfs solid material Membrane-enclosed vesicle detaches from cell surface and moves into cytoplasm Fuses with lysosomes and contents are digested by lysosome's enzymes

30 Active Transport Processes Endocytosis Ingestion of materials by the cell Requires energy Pinocytosis Cell Drinking Cell membrane invaginates forming a vesicle to engulf small solids and liquids into the cell

31 Active Transport Processes Endocytosis Ingestion of materials by the cell Requires energy Receptor-Mediated Endocytosis Membrane proteins bind to specific molecules present in extracellular fluid Region invaginates forming vesicles bringing molecules into cell

32 Active Transport Processes Exocytosis Movement of vesicle-packaged materials out of the cell Requires energy Membrane of a vesicle fuses with plasma membrane and extrudes its contents