Foundation year BIOLOGY-BIOL (101) Cell Structure & Function Dr. Huda Kassem

Points to think Cell Structure and Function 1.What is a cell? 2.Why are most cells small? 3.What do prokaryotic and eukaryotic cell have in common? 4.How are cells organized? 5.How do things move across the plasma membrane? 6.What is cellular respiration?

What does the cell theory tell us? Cell Structure and Function 1.A cell is the basic unit of life. 2.All living things are made up of cells. 3.New cells arise from preexisting cells.

Why are most cells small? Cell Structure and Function Consider the cell surface-area-to-volume ratio:  Small cells have a larger amount of surface area compared to the volume.  An increase in surface area allows for more nutrients to pass into the cell and wastes to exit the cell more efficiently.

3.1 What is a cell? 6   1 mm 2 = 6 mm 2 (1 mm) 3 = 1 mm 3 (2 mm) 3 = 8 mm 3 Surface area Volume = 1 mm2 mm Surface area (square mm) Volume (cubic mm) 6   4 mm 2 = 24 mm 2

What are some common microscopes used to view cells? Cell Structure and Function 1. Compound light microscope Lower magnification. Uses light beams to view images. Can view live specimens. 2. Transmission electron microscope 2-D image. Uses electrons to view internal structure. High magnification, no live specimens. 3. Scanning electron microscope 3-D image. Uses electrons to view surface structures. High magnification, no live specimens.

The two major types of cells in all living organisms? Cell Structure and Function 1. Prokaryotic cells  Thought to be the first cells to evolve.  Lack a nucleus.  Represented by bacteria and archaea. 2. Eukaryotic cells  Have a nucleus that houses DNA.  Many membrane-bound organelles.

Common contents of prokaryotic and eukaryotic cells? Cell Structure and Function A plasma membrane that surrounds and delineates the cell. A cytoplasm that is the semi- fluid portion inside the cell that contains organelles. DNA.

Where did eukaryotic cells come from? 3.2 How cells are organized chloroplast 3. Cell gains protomitochondria. Animal cell Plant cell mitochondrion protochloroplast DNA 2. Cell gains an endomembrane system by proliferation of membrane. 1. Cell gains a nucleus by the plasma membrane invaginating and surrounding the DNA with a double membrane. proto- mitochondrion 4. Cell gains protochloroplasts.

What do eukaryotic cells look like? 3.2 How cells are organized phospholipid protein CYTOSKELETON: maintains cell shape and assists movement of cell parts: Actin filaments: protein fibers that play a role in movement of cell and organelles NUCLEUS: Cytoplasm: semifluid matrix outside nucleus that contains organelles Intermediate filaments: protein fibers that provide support and strength ENDOPLASMIC RETICULUM: Microtubules: cylinders of protein molecules present in cytoplasm, centrioles, cilia, and flagella Vesicle: membrane-bounded sac that stores and transports substances Chromatin: diffuse threads containing DNA and protein chromatin nucleolus 50 nm plasma membrane nuclear envelope endoplasmic reticulum Centrioles: short cylinders of microtubules of unknown function Centrosome: microtubule organizing center that contains a pair of centrioles Lysosome: vesicle that digests macromolecules and even cell parts Golgi apparatus: processes, packages, and secretes modified cell products Polyribosome: string of ribosomes simultaneously synthesizing same protein Mitochondrion: organelle that carries out cellular respiration, producing ATP molecules Ribosomes: particles that carry out protein synthesis Smooth ER: lacks ribosomes, synthesizes lipid molecules Rough ER: studded with ribosomes, processes proteins Nucleolus: region that produces subunits of ribosomes Nuclear envelope: double membrane with nuclear pores that encloses nucleus © Alfred Pasieka/Photo Researchers, Inc. Plasma membrane: outer surface that regulates entrance and exit of molecules

What are some characteristics of the plasma membrane? 1.It is a phospholipids bilayer. 2.It is embedded with proteins that move in space. 3.It contains cholesterol for support. 4.It contains carbohydrates on proteins and lipids. 5.Selectively permeable 1.It is a phospholipids bilayer. 2.It is embedded with proteins that move in space. 3.It contains cholesterol for support. 4.It contains carbohydrates on proteins and lipids. 5.Selectively permeable 3.3 The plasma membrane and how substances cross it Outside Inside plasma membrane protein filaments of cytoskeleton cholesterol carbohydrate chain hydrophobic tails phopspholipid bilayer hydrophilic heads

What does selectively permeable mean? The membrane allows some things in while keeping other substances out 3.3 The plasma membrane and how substances cross it macromolecule H2OH2O aquaporin protein noncharged molecules phospholipid molecule   +

How do things move across the plasma membrane? Cell Structure and Function 1. Diffusion. 2. Osmosis. 3. Facilitated transport. 4. Active transport. 5. Endocytosis and exocytosis.

What are diffusion and osmosis? 1.Diffusion: is the random movement of molecules from a higher concentration to a lower concentration. 2. Osmosis: is the diffusion of water molecules. 3.3 The plasma membrane and how substances cross it A. Initial conditionsB. Equilibrium conditions time cell particlewater plasma membrane

How does tonicity change a cell? Hypertonic solutions have more solute than the inside of the cell and lead to lysis (shriveling) Hypotonic solutions have less solute than the inside of the cell and lead to crenation (brusting) Isotonic solutions have equal amounts of solute inside and outside the cell and thus does not affect the cell 3.3 The plasma membrane and how substances cross it H2OH2O H2OH2O c. Isotonic solution (same solute concen- tration as in cell) b. Hypotonic solution (lower solute concen- tration than in cell) A. Hypertonic solution (higher solute concen- tration than in cell)

What are facilitated transport and active transport? 3. Facilitated transport : is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier 4. Active transport: is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier 3.3 The plasma membrane and how substances cross it Inside Outside K+K+ K+K+ K+K+ K+K+ K+K+ P Na + ATP ADP

What are endocytosis and exocytosis? 5. Endocytosis transports molecules into the cell via invagination of the plasma membrane to form a vesicle. 6. Exocytosis transports molecules outside the cell via fusion of a vesicle with the plasma membrane 3.3 The plasma membrane and how substances cross it a. Endocytosis b. Exocytosis vesicle Inside Outside substances taken in substances released

Cell Structure and Function 1.Nucleus. 2.Ribosome's. 3.End membrane system.

What is the structure and function of the nucleus? 1.Bound by a porous nuclear envelope. 2.Houses DNA and associated proteins called chromatin. 3.Contains nucleoplasm. 4. Nucleolus region(s) that contain ribosomal RNA (rRNA) 3.4 The nucleus and the production of proteins nuclear pores nuclear envelope chromatin nucleolus rough ER smooth ER

Cell Structure and Function What is the structure and function of ribosome's? 1.Organelles made of RNA and protein. 2.Found bound to the endoplasmic reticulum and free floating in the cell. 3.Site of protein synthesis.

Cell Structure and Function A series of membranes in which molecules are transported in the cell. It consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes and vesicles.

3.4 The nucleus and the production of proteins incoming vesicle protein enzyme secretory vesicle ribosome lipid secretion Nucleus plasma membrane Golgi apparatus modifies lipids and Proteins from the ER; sorts and packages them in vesicles transport vesicle takes proteins to Golgi apparatus rough endoplasmic reticulum synthesizes proteins And packages them in vesicles smooth endoplasmic reticulum synthesizes lipids and has various other functions transport vesicle takes lipids to Golgi apparatus lysosome contains digestive enzymes that break down cell parts or substances entering by vesicles

Cell Structure and Function Summary of the parts of the endomembrane system? 1. Rough endoplasmic reticulum: studded with ribosome used to make proteins. 2. Smooth endoplasmic reticulum: lacks ribosome but aids in making carbohydrates and lipids. 3. Golgi apparatus: flattened stacks that process, package and deliver proteins and lipids from the ER. 4. Lysosomes: membranous vesicles made by the Golgi that contain digestive enzymes. 5. Vesicles: small membranous sacs used for transport

Cell Structure and Function What is cytoskeleton?  A series of proteins that maintain cell shape as well as anchors and/or moves organelles in the cell.  Made of 3 fibers: large microtubules, thin actin filaments and medium-sized intermediate filaments.

1.Both are made of microtubules. 2.Both are used in movement. 3.Cilia are about 20x shorter than flagella. 3.5 The cytoskeleton and cell movement microtubules cilia sperm secretory cell flagellum c. b. plasma membrane

1)A highly folded organelle in eukaryotic cells. 2)Produces energy in the form of ATP. 3)They are thought to be derived from an engulfed prokaryotic cell. 3.6 Mitochondria and cellular metabolism cristae matrix 200 nm intermembrane space outer membrane inner membrane

Cell Structure and Function 1.Most enzymes are proteins. 2.Enzymes are often named for the molecule that they work on or substrates. 3.Enzymes are specific to what substrate they work on. 4.Enzymes have active sites where a substrate binds. 5.Enzymes are not used up in a reaction but instead are recycled. 6.Some enzymes are aided by non-protein molecules called coenzymes. Enzymes important in cellular respiration & many activities in the cell

How do enzymes work? 3.6 Mitochondria and cellular metabolism products substrate enzyme active site enzyme product substrates enzyme active site enzyme enzyme-substrate complex Degradation A substrate is broken down to smaller products. Synthesis Substrates are combined to produce a larger product. enzyme-substrate complex

What is cellular respiration? Production of ATP in a cell Includes: 1.Glycolysis. 2.Citric acid cycle. 3. Electron transport chain. 3.6 Mitochondria and cellular metabolism Glycolysis glucose mitochondrion oxygen pyruvate ATP Inside cell Outside cell electrons transferred by NADH electrons transferred by NADH Citric acid cycle Electron transport chain ATP

What happens in glycolysis step 1 of cellular respiration? Cell Structure and Function A. Glycolysis 1.Occurs in the cytoplasm. 2.Breaks glucose into 2 pyruvate. 3.NADH and 2 ATP molecules are made. 4.Does not require oxygen.

Cell Structure and Function B. Citric acid cycle 1.A cyclical pathway that occurs in the mitochondria. 2.Produces NADH and 2 ATP. 3.Requires oxygen. What happens in glycolysis step 2 of cellular respiration?

Cell Structure and Function C. Electron transport chain 1.Series of molecules embedded in the mitochondrial membrane. 2.NADH made in steps 1 and 2 carry electrons here ATP are made depending on the cell 4.Requires oxygen as the final electron acceptor in the chain. ?

Cell Structure and Function Fermentation I.Occurs in the cytoplasm. II.Does not require oxygen. III.Involves glycolysis. IV.Makes 2 ATP and lactate in human cells. V.Is important in humans for a burst of energy for a short time. How can a cell make ATP without oxygen

Cell Structure and Function i.Other carbohydrates. ii.Proteins. iii.Lipids.