Cell Structure & Function Source: http://koning.ecsu.ctstateu.edu/cell/cell.html

Definition of Cell A cell is the smallest unit that is capable of performing life functions.

Examples of Cells Muscle Cell Skin Cell Bacteria Red Blood Cell Nerve Cell

Prokaryotic Eukaryotic Two Types of Cells Prokaryotic Eukaryotic

Prokaryotic Do not have structures surrounded by membranes Few internal structures One-celled organisms, Bacteria http://library.thinkquest.org/C004535/prokaryotic_cells.html

Prokaryotic Cell

Eukaryotic Contain organelles surrounded by membranes Most living organisms Plant Animal http://library.thinkquest.org/C004535/eukaryotic_cells.html

Eukaryotic Cells Eukaryotic cells -possess a membrane-bound nucleus -are more complex than prokaryotic cells -compartmentalize many cellular functions within organelles and the endomembrane system -possess a cytoskeleton for support and to maintain cellular structure

“Typical” Animal Cell http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

Eukaryotic Cells

Eukaryotic Cells Nucleus -stores the genetic material of the cell in the form of multiple, linear chromosomes -surrounded by a nuclear envelope composed of 2 phospholipid bilayers -in chromosomes – DNA is organized with proteins to form chromatin

Eukaryotic Cells

Cell Parts Organelles

Surrounding the Cell

Cell Membrane Outer membrane of cell that controls movement in and out of the cell Phospholipid bilayer Composed of multiple types of proteins http://library.thinkquest.org/12413/structures.html

Function of Cell Membrane Cell membrane provides gateway to most of the body’s metabolic reactions Major Processes: Passive and Active Transport Passive Diffusion: Diffusion and Filtration Diffusion: process by which molecules move away from region of high concentration to low concentration (concentration gradient) Simple Diffusion: Molecules can move freely through the membrane (osmosis: diffusion of water) Facilitated Diffusion: Provides passage of larger molecules too big to move through membrane

Function of Cell Membrane Active Transport: requires ATP to move molecules across membrane Molecules can move across gradient Sodium-Potassium Pump: carries ions into nerve cells via ATP Exocytosis: moves substances out of the cell Endocytosis: moves substances in the cell https://www.youtube.com/watch?v=DuDmvlbpjHQ

Inside the Cell

Nucleus Directs cell activities Separated from cytoplasm by nuclear membrane Contains genetic material - DNA

Nuclear Membrane Surrounds nucleus Made of two layers Phospholipid bilayer Openings allow material to enter and leave nucleus http://library.thinkquest.org/12413/structures.html

Nucleolus Inside nucleus Site of ribosome production Contains RNA to build proteins Site of translation http://library.thinkquest.org/12413/structures.html

Cytoplasm Gel-like mixture (cytosol) Surrounded by cell membrane Mostly composed of water Anchors organelles within the cell Surrounded by cell membrane Where most of the human body’s metabolic reactions occur

Mitochondria Produces energy through chemical reactions – breaking down fats & carbohydrates Controls level of water and other materials in cell Found in higher concentrations in higher energy organs (i.e. liver, muscle) http://library.thinkquest.org/12413/structures.html

Mitochondria

Endoplasmic Reticulum Moves materials around in cell Smooth type: lacks ribosomes; involved in lipid metabolism Rough type (pictured): ribosomes embedded in surface Functions to fold and transport proteins across the cell http://library.thinkquest.org/12413/structures.html

Ribosomes Each cell contains thousands of ribosomes Site of protein synthesis Found on ribosomes & floating throughout the cell http://library.thinkquest.org/12413/structures.html

Golgi Bodies Protein 'packaging plant' Move materials within the cell Move materials out of the cell http://library.thinkquest.org/12413/structures.html

Lysosome Digestive 'plant' for proteins, fats, and carbohydrates Transports undigested material to cell membrane for removal Cell breaks down if lysosome structure is disrupted. http://library.thinkquest.org/12413/structures.html

Peroxisomes Membranous sacs that contain oxidase enzymes Work to detoxify harmful substances Most numerous in liver and kidney cells

Endomembrane System (4.6 – 4.9) Series of organelles responsible for: Modifying protein chains into their final form Synthesizing of lipids Packaging of fully modified proteins and lipids into vesicles for export or use in the cell And more that we will not cover!

Cell Structure All Cells have: an outermost plasma membrane genetic material in the form of DNA cytoplasm with ribosomes

Why Are Cells So Small? (4.2) Cells need sufficient surface area to allow adequate transport of nutrients in and wastes out. As cell volume increases, so does the need for the transporting of nutrients and wastes.

Why Are Cells So Small? However, as cell volume increases the surface area of the cell does not expand as quickly. If the cell’s volume gets too large it cannot transport enough wastes out or nutrients in. Thus, surface area limits cell volume/size.

Why Are Cells So Small? Strategies for increasing surface area, so cell can be larger: “Frilly” edged……. Long and narrow….. Round cells will always be small.