BIOLOGY UNIT THREE AREA OF STUDY #1: MOLECULES OF LIFE

BIOLOGY UNIT THREE AREA OF STUDY #1: MOLECULES OF LIFE
EXAM REVISION LECTURE CHP 2: MEMBRANES AND CELL ORGANELLES

CHP 2 TOPIC 1: CELLS Cell Types
Viruses: not really cells; share some characteristics with living things including; Genetic material (DNA or RNA) Protein coat (known as a capsid); some also envelop themselves courtesy of infected host membrane Enzymes Prokaryotic Cells: Include bacteria (Monera), archaebacteria and eubacteria Smallest living cells (most bacteria less than 1 micron i.e. <1/1000mm) All single celled organisms (but some form colonies) Have a cell membrane and cytosol Lack membrane bound organelles Have no nuclear membrane Have just one, circular chromosome; may have many small rings of DNA called plasmids contain ribosomes (organelle not membrane bound) May contain fimbria (hairline structures used for attachment); flagellum - used for movement

Eukaryotic Cells Larger than prokaryotic cells (ranging from 10 to 150 microns) Include the Kingdoms: animal; plants; fungi & protista (protozoa) Some are unicellular (single celled) others are multicellular (with many specialised cells) All contain membrane bound organelles suspended in a fluid known as cytosol (membranes, organelle and cytosol together is known as cytoplasm Membrane is a liquid lipid bilayer (two layers of phospholipids) Have many linear chromosomes Protista Cells eukaryotic – have a nucleus example: paramecium; euglena, amoeba unicellular about 100 microns cell membrane may contain chloroplasts; cell wall Fungi Cells eukaryotic can be single or mutlicellular cell wall – made of chitin Plant Cells multicellular – often square in shape cell membrane (often not visible) cell wall made of cellulose some cells contain plastids (i.e. chloroplasts) vacuoles Animal Cells multicellular no cell wall or vacuole centrioles (involved in cell division)

The light microscope has a limit of resolution of about 200 nm (0
The light microscope has a limit of resolution of about 200 nm (0.2 µm). This limit is due to the wavelength of light ( µm). Cells observed under a light microscope can be alive, or fixed and stained

Topic CHP2.1 Questions: List up to 7 characteristics of all living things: Which of the following would be not be visible under a low-power light microscope: Guard Cell; White Blood Cell; paramecium; nucleus; ribosome Which of the following could be used to examine living cells: Light microscope or Transmission Electron Microscope List three characteristics of each of the following: Protozoan Cell: ___________________, ________________________ & ________________________ Bacteria Cell: : ___________________, ________________________ & ________________________ Plant Cell: : ___________________, ________________________ & ________________________ True False: Bacteria, Plant & Fungi cell walls are made of polysaccharides True False : The cell wall of Fungi is made of chitin True/ False: Plasmids are circular units of DNA What name is given to inert viruses (those not infecting a host): _______________ What name is given to the protein coat around a viruse: _____________________ / 9 Marks

CHP 2 TOPIC 2: CELL ORGANELLES
Organelle: structural unit in cells that performs a key function in cellular metabolism Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Cell Membrane also called: cytoplasmic/ plasma membrane Double layer of phospholipids embedded with proteins, glycoproteins and carbohydrates encloses cell contents regulates the movement of materials into and out of cells maintain cell shape communicate with other cells √ Nucleus Surrounded by a double membrane (2 membranes!). Contains chromosomes and nucleolus Some cells have more than 1 information in the chromosomes controls the production of proteins in the cell- control cellular metabolism x Nuclear Membrane Pores in membrane big enough for RNA to leave regulates the movement of materials between itself

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Nucleolus 1-3 inside a nucleus A granular structure in the nucleus, made up of protein and RNA site of manufacture of ribosomal RNA x √ Mitochondria (sing: mitochondrion) A few to thousands in cytoplasm Sacs made up of 2 membranes . Inner membrane folded to create cristae (increase SA: V).Fluid filled matrix site of aerobic cellular respiration, they are responsible for most of the cells energy production most abundant in cells with high energy needs; muscle cells, kidney tubules

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Ribosomes Some are free in the cytosol (produce protein for cell) others are free floating (proteins for export) Small spherical organelles composed of RNA and protein Consist of two sub-units the site of protein synthesis √ Smooth Endoplasmic Reticulum throughout the cytoplasm Network of membranes creating channels in the cytoplasm from the nucleus to the cell membrane the site of lipid synthesis transport of many materials throughout the cell. Abundant in cells which produced steroid hormones also contains enzymes for detoxifying chemicals including drugs and pesticides x

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Nucleolus 1-3 inside a nucleus A granular structure in the nucleus, made up of protein and RNA site of manufacture of ribosomal RNA x √ Mitochondria (sing: mitochondrion) A few to thousands in cytoplasm Sacs made up of 2 membranes . Inner membrane folded to create cristae (increase SA: V).Fluid filled matrix site of aerobic cellular respiration, they are responsible for most of the cells energy production most abundant in cells with high energy needs; muscle cells, kidney tubules

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Rough Endoplasmic Reticulum throughout the cytoplasm Often associated with nuclear memb. A network of membranes creating channels in the cytoplasm. Studded with ribosomes transport and folding of proteins produced by ribosomes synthesis of gycoproteins parts become pinched off to become vesicles for transport to the membrane or to other organelles x √ Golgi Complex also called golgi complex Stacks of flattened sacs packages proteins and glycoproteins into vesicles for secretion from the cell or to be sent to other organelles Synthesises cellulose in plant cells abundant in cells that export cell products

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Lysosome throughout cytoplasm A membrane sack containing many digestive enzymes contain enzymes which digest ingested materials and wastes. Important in programmed cell death (apoptosis) x √ Vacuole One large in mature plant cells. Smaller (vesicles) in animal cells) Appear clear when seen through a microscope A membrane bound sac containing fluid, sugars and ions important in cell turgor in plant cells pressure of fluid in large vacuole helps maintain cell shape storage storage of sugars, ions and food

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Chloroplasts Few to many in cells which photosynthesis Surrounded by a double membrane, contains stacks of membranes (grana) embedded in less dense membrane and fluid (stroma) site of photosynthesis grana (or thylakoid membranes) contain chlorophyll, the pigment which traps light energy Abundant in leaf cells x √ Centriole Near the nucleus in animal cells Near the poles in dividing animal cells A pair of cylindrical structures made up of several smaller tubes The spindle forms between centrioles during cell division

Name & Location Description/ Diagram Function Present in Prokaryotes Animal Plants Flagella or Cilia Extension(s) of the cell membrane Made of membrane material and microtubules, they protrude from the cell. Note, prokaryotic flagella lack membrane material provides a means of movement of the cell or of the fluid surrounding the cell √ Cell Wall (not really an organelle!) A layer of cellulose (in plants) secreted by the cell (see golgi complex) and completely surrounding membrane. Note: cellulose only in plant cells provides structural support and defines the shape of cells x

Topic CHP2.2 Questions: / 10 Marks
The cellular organelles which assemble polypeptides are called? _________________ Pancreatic cells will incorporate radioactively labelled amino acids into proteins. Proteins can therefore be labelled and tracked within a cell. If we were tracking a pancreatic enzyme that was to be secreted, the most likely pathway of movement of this protein in the cell would be: Endoplasmic reticulum to golgi body to nucleus Golgi body to ER to lysosome Nucleus to ER to golgi body ER to golgi body to secretory vesicles The purpose of the cristae in mitochondria is To provide greater SA within the organelle To store chemicals To provide a surface for the process of photosynthesis to occur To provide structural support Rough ER are called rough because: ______________ In what type of plant cells would you expect to find mitochondria? _____________ Which 4 organelles contain nucleic material? _____________________________________ Outline the role of the following organelles in protein manufacture: Nucleus Ribosomes Rough ER Golgi Apparatus Secretory vesicles True/ False: Lysosmes are involved in apoptosis? Which organelles have a double membrane?__________________________________________ Name three organelles you can see and three you can’t see under a light microscope in an animal cell. ____________________________________, ________________________________, _______________________________ / 10 Marks

CHP 2 TOPIC 3 ENZYMES A catalyst is any chemical which speeds up the rate of a chemical reaction without itself being used up in the reaction. Biological catalysts are enzymes. Enzymes are protein molecules manufactured by cells in the ribosomes. are proteins that act on other molecules are organic catalysts are protein molecules that increase the rate of reactions that occur inside the organism. are generally intracellular (exception: digestive enzymes) some require a non-protein cofactor (i.e vitamins, CoQ10) before they can act have a region, known as the active site, that alligns with a particular substrate the compounds obtained as a result of the enzyme action are called the products enzymes are highly specific in their action. Each enzyme acts on a particular substrate.

Enzymes are organic catalysts.
Substrate Enzymes are organic catalysts. 1 Active Site Enzyme Product Enzyme-Substrate Complex 3 2 Enzyme Menu 15

REVERSIBLE INHIBITION IRREVERSIBLE INHIBITION
Many enzymes lower the activation energy required to get a reaction going Enzymes are sensitive to pH. They will only work in optimum pH range Optimum pH differs for different enzymes Enzymes are denatured if the pH varies from the optimum Enzymes are temperature sensitive Most enzymes work best at temps between degrees celcius The rate of any reaction is slower at lower temps At temps above 40 degrees most enzymes denature Some bacterial enzymes can exist in hot temps Enzyme action can be affected by the presence of other molecules which may inhibit the action of the enzyme Inhibition of enzymes may be reversible or irreversible REVERSIBLE INHIBITION Competitive Inhibition: molecule competes with the substrate for binding to the enzymes active site – temporary Non-Competitive Inhibition: Molecule binds with the enzyme in a part of the enzyme that is not the active site, but alters the shape of the enzyme molecule IRREVERSIBLE INHIBITION Denaturing; caused by heat, pH or other chemicals the seondary or tertiary structure is lost Binding of Poisons: many pisons are chemicals which bind irreversibly to enzymes, stopping their function. Examples: some antibiotics, gases, heavy metals

Some cofactors are inorganic ions
Cofactors: some enzymes require another chemical component attached to the protein to be active: Some cofactors are inorganic ions Organic cofactors are called coenzymes Most coenzymes are carrier molecules transferring electrons or ions from one reactant to another in a biological reaction: NADH, NADPH and FADH2 are important coenzymes ATP is a coenzyme This complementary fitting of shapes is known as the ‘lock and key’ theory of enzyme action. in some cases, the shape of the active site varies slightly from that of the substrate and the two fit only after the substrate induces a complimentary shape at the active site theory of enzyme action.

Rate of reaction will be dependent upon amount of:
substrate concentration enzyme concentration cofactors concentration presence of inhibitors such as poisons

Topic CHP2.3Questions: Name four factors that influence that rate of enzyme action: ________________, _________________, ______________________ & ______________________ The amount of energy required to initiate a reaction is called what: ___________ ____________ A biological catalyst is called an: _____________________ In regards to enzyme inhibition, denaturing is: reversible / irreversible A molecule which competes with the substrate for binding to the ensymes active site is called what: ___________________ _________________ The action of enzymes is: random/ dependent upon diploar bonds/ highly specific With regards to theories of enzyme action, the perfect fit of enzyme and substrate is called the ________________ theory; when the substrate is slightly different to that of the active site, the theory of enzyme action is known as the ___________ & ______________ theory / 7 Marks

CHP 2 TOPIC 4 MEMBRANES & MOVEMENT OF MATERIALS
All cells are surrounded by a cellular membrane (also known as plasma membrane) Cell membranes are selectively/ semi/ partially permeable Control movement into and out of cell; communication between cells; recognition by other cells Less than 0.01 microns thick or 1/ mm or 10 nanometers (scanning electron can see down to 2 nanometers!) Cell membranes are composed of a phospholipid bilayer Proteins are embedded in the bilayer Carbohydrate chains are involved in cell recognition Cholesterol (lipid- steroid) also often embedded in membrane- aide fluidity The phospholipids and proteins allow the movement of substances in and out of cell

There are carrier proteins that regulate transport and diffusion
Channel Proteins These proteins are used in intercellular communication. In this animation you can see the a hormone binding to the receptor. This causes the receptor protein release a signal to perform some action. Receptor Proteins There are carrier proteins that regulate transport and diffusion

Topic CHP2.4 Questions: List four roles for cell membranes:____________, ______________, __________, ______________ List 5 molecules found in a typical cell membrane::____________, ______________, __________,______________ & __________________ True/ false: you can see a membrane under a scanning electron microscope ? _________________ / 3 Marks

CHP 2 TOPIC 5 MOVEMENT OF MATERIALS THROUGH MEMBRANES
Diffusion is the ‘tendency’ of particles of gases, liquids and solutes to dispense randomly and fill available space Rate of diffusion increases with: temperature increase/ concentration increase Particles random movement from where they are in high concentration to were they are in low concentration This is commonly referred to as moving along a concentration gradient Diffusion does not require energy – passive transport Does not have to occur through a permeable membrane

Osmosis is the net movement of water molecules across a differentially permeable membrane, from an area of low solute concentration to an area of high solute concentration). note: you don’t usually refer to water with the word concentration Water can only move passively (through osmosis) Water (H2O)molecules are smaller glucose (C6H12O6) etc and can move readily The net movement is ‘overall’ as water moves both directions When water is in solution, solutes often combine (NACl) and reduce ability of water to move Intercellular fluid surrounding cells is usually isotonic (the same) asthe intracellular fluid (in cell Surrounding cell Animal cell Plant cell Isotonic solution- solute concentration the same as cell Water moves into and out of the cell at the same rate- no net movement Hypotonic solution –a lower solute concentration than cell Water enters the cell causing it to swell. Too much osmotic pressure - it bursts Water enters cells and passes into vacuole. Vacuole squeezes cytoplasm against cell wall. Cell becomes turgid Hypertonic solution – higher solute concentration than the cell Net movement of water out of cell, causing shrinkage. Cell may die Water leaves cell causing plasmolysis (shrinkage). Cell becomes flacid.

Movement Type Description Direction Of Movement Active/ Passive Simple Diffusion Small uncharged particles (water, oxygen) and lipid soluble (alcohol, urea) molecules diffuse from an area of high to low concentration through phospholipid bilayer High to Low solute Passive Channel Mediated / Facilitated Diffusion In some cases the channel proteins simply act as a passive pore. Molecules will randomly move through the opening in a process called diffusion. Ions, glucose, amino acids Active Transport The transport of molecules across cell membranes against a concentration gradient. Active transport occurs through protein channels and requires energy in the form of ATP I.e. potassium ions , Low to high Active Endocytosis Pinocytosis (fluid) and phagocytosis large particles and debris) Cells are able to take in larger quantities of solids and liquids by endocytosis. Parts of the membrane fold around the material and pinch off, inclosing the material in a vesicle. Process requires energy Exocytosis Cells secrete cell products and eliminate wastes by exocytosis.vesicles fuse with membrane, open out and spilll contents into intercellular fluid. Process requires energy High to Low solute High to Low solute

Topic CHP2.5 Questions: Name two factors that can influence the rate of diffusion: _______________, ____________ Diffusing particles: move along/ against/ up a concentration gradient True/ False: Diffusion does not require ATP True/ False: Diffusion take place through a differentially permeable membrane True / False: Water can be moved against a concentration gradient with the use of ATP Which of the following is the larger molecule (circle): a monosaccharide/ water Name three factors that influence the net movement of water molecules through a differentially permeable membrane: _______________, ____________ & _______________ Fresh water fish cells would be (circle): isotonic/ hypertonic/ hypotonic in comparison to their environment Cells of a salt water fish placed into freshwater would: expand & burst/ shrivel Plant cells placed in a hypertonic solution will undergo: plasmolysis/ become turgid pressure caused by water within the cell is called: ______________ pressure Active transport requires which of the following: protein channels, ATP Synthase, ATP, concentration gradient True/ False: Facilitated Diffusion/ Channel mediated diffusion requires ATP Name two forms of Exocytosis:____________________ & _______________________ Name four molecules that can move through a phospholipid bilayer by simple diffusion: __________________, _______________________, __________________, _____________ / 15 Marks

CHP 2 TOPIC 6 SURFACE AREA TO VOLUME & CELL SIZE
A few types of cells are large enough to be seen by the unaided eye. The human egg (ovum) is the largest cell in the body, and can (just) be seen without the aid of a microscope. Most cells are small for two main reasons: a). The cell’s nucleus can only control a certain volume of active cytoplasm. b). Cells are limited in size by their surface area to volume ratio. A group of small cells has a relatively larger surface area than a single large cell of the same volume. This is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface. As a cell grows larger at some point its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell's need. (= Fick’s Law – something you need to learn well). Rate of diffusion α Surface Area x Concentration Difference Distance Chapter 2 - Cells: Structure & Function

CHP 2 TOPIC 6 SURFACE AREA TO VOLUME & CELL SIZE
Cellular environments and cell size All cells need to exchange materials with their environments. They need to take in gases, water and nutrients and get rid of wastes. Exchange of materials can only occur through the cell’s membrane. The larger a cell becomes, the smaller its surface area becomes in relation to its volume. Look at these cubes to see the difference increasing size has on the ratio between surface area and volume When a cell grows its volume grows at a greater rate than its surface area. If a cell becomes to large they are unable to carry out sufficient exchange of materials with the environment. Q. how would Fick’s Law influence the potential size of Prokaryotic organisms? Chapter 2 - Cells: Structure & Function

Topic CHP2.6 Questions: Name on cell visible with the naked eye? ______________ List two factors that limit cell size:________________________, ______________ As a cell grows larger at some point its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell's need. This is known as_____________________ Law Find the SA: V of the following: Which cube has the greater SA:V?

CHP 2 TOPIC 7 CELL SPECIALISATIION -TISSUES ORGANS & SYSTEMS
In most multicellular organisms, we find the following organization: Cellular Level: The smallest unit of life capable of carrying out all the functions of living things. Tissue Level: A group of cells that performs a specific function in an organism. Organ Level: Several different types of tissue that function together for a specific purpose. Organ System Level: Several organs working together to perform a function. The different organ systems in a multicellular organism interact to carry out the processes of life

Absorption of materials
CHP 2 TOPIC 7 CELL SPECIALISATIION -TISSUES ORGANS & SYSTEMS Eukaryotic cells vary a great deal in structure. Variations in cell structure are related to function. Cells vary in the number of each organelle present and in their shape and life cycle. Function Example Structure Absorption of materials A cell lining the intestine Large surface area created by folds of membrane known as microvilli. Large number of mitochondria to provide energy for active transport A root hair cell Large surface area due to long, elongated shape. Large number of mitochondria to provide energy for active transport Photosynthesis A leaf cell Large number of chloroplasts, large vacuole for water storage Communication A motor neuron Elongated shape, large number of mitochondria for energy production Transport A sieve tube cell (plant vascular bundle) Cells of the phloem vessels in plants have thickened cell walls, elongated shape and porous ends

Topic CHP2.7 Questions: True/ False: cells in an organ are all made of the same tissue and cell type? ______ How do single celled organisms function without specialised cells and tissues? Explain: _________________________________________________________________________________________________________________________________________________________________________________________________________ Name two characteristics of: root hairs that supports its function to absorb materials from its environment: _______________, ____________________ Microvilli that supports its function to absorb materials from its environment: _______________, ____________________ Leaf cell to photosynthesise: _______________, ____________________ / 3 Marks

CHP 2 TOPIC 8 CONNECTIONS BETWEEN CELLS
Although some cells like blood cells, are free to move as individuals around the body, most cells remain as a group. To assist this ‘community’ of cells are three types of junctions (joins) including: Occluding junctions: simply where one cell comes into contact with another (no movement of material between them) Communicating junctions (gap junctions): also known as gap junctions. Consist of protein lined pores between the membrane of adjacent cells. The proteins are aligned like a series of rods with a gap (pore) in the middle of them. This bridge between cells enables the passage of ions, sugars, amino acids, other small particles and even electrical signals between the two cells. (example: electrical impulse in the heart) Anchoring Junctions (desmosomes): most common form of junction in epithelial cells (skin, uterus, lining cells!). Dense proteins protrude from the cytosol of one cell into the other to ‘anchor’ the cells together.

Chapter 2 - Membranes and cell organelles
Communicating Junctions right .. Anchoring junctions below Chapter 2 - Membranes and cell organelles

Connections between plant cells
Plasmodesmata (singular: plasmodium) is the name given for the structure that joins plant cells. Because of the way in which cell walls are built, the gap or pore between two cells is continuous and lined with cell membrane. The structure that bridges the gap is continuos with smooth endoplamsic reticulum. Chapter 2 - Membranes and cell organelles

Topic CHP2.8 Questions: List three types of communicating junctions:
____________________, ___________________________, _________________ What is the name given to the structure that joins plant cells together: __________________ True/ False: the cytoplasm of one plant cell is continuous with the cytoplasm of another plant cell Which macromolecule constitutes the gap junction structure: ________________ Name this structure: Dense proteins protrude from the cytosol of one cell into the other to anchor the cells together: ____________________ /5 Marks

BIOLOGY UNIT THREE AREA OF STUDY #1: MOLECULES OF LIFE

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