Cells Unit 1 PDF

Cells Unit 1 All living things carry out seven basic functions integral to survival Metabolism – Living things undertake essential chemical reactions Reproduction – Living things produce offspring, either sexually or asexually Sensitivity – Living things are responsive to internal and exter...

Cells Unit 1 All living things carry out seven basic functions integral to survival Metabolism – Living things undertake essential chemical reactions Reproduction – Living things produce offspring, either sexually or asexually Sensitivity – Living things are responsive to internal and external stimuli Homeostasis – Living things maintain a stable internal environment Excretion – Living things exhibit the removal of waste products Nutrition – Living things exchange materials and gases with the environment Growth / Movement – Living things can move and change shape or size There are four basic structures common to all cells Plasma Membrane: All cells must have an outer border to maintain an internal chemistry that is different to the exterior Genetic Material: All cells must contain coded instructions that function to control internal activities within a cell Ribosomes: All cells must contain ribosomes to translate the cell’s coded instructions into functional elements Cytoplasm: All cells must contain an internal fluid that functions as a reaction medium for all necessary metabolic processes  Prokaryotic Cell Structure The genetic material is found within a region of the cytoplasm called the nucleoid The ribosomes within the cell that are responsible for protein synthesis are characteristically small in size (70s) Prokaryotic cells all possess a cell wall and may possess an additional outer covering They may possess hair-like extensions called pili, that aid in adhesion Additionally, many prokaryotes may possess several whip-like projections called flagella, which facilitate movement When drawing prokaryotic cells, the following shouldshould The genetic material be included: be drawn as a loop Pili and flagella should project from the cell wall Ribosomes should be drawn as filled in dots and labelled as 70S in size A flagellum should be thicker than pili and significantly longer in length The shape should be appropriate to the type of bacteria  Eukaryotes Organisms whose cells contain a nucleus and have numerous membrane-bound organelles They have a greater level of structural complexity 1. Animal Cell: Have no cell wall and undertake heterotrophic nutrition 2. Plant Cell: Have a cell wall and undertake autotrophic nutrition 3. Fungi: Have a cell wall and undertake heterotrophic nutrition Protist: Any eukaryotic organism that does not belong to the animal, plant or fungal kingdoms The genetic material is found within a double-membrane structure called the nucleus The ribosomes within the cell that are responsible for protein synthesis are comparatively larger in size Eukaryotes all share a number of membrane-bound organelles – including mitochondria, endoplasmic reticulum, golgi apparatus and vesicles Plant cells possess chloroplasts and have a large, fluid-filled When drawing Eukaryotic Animal cells, the following should The nucleus should be included be a double membrane structure with pores The ER network should be shown as connected membranes, but golgi membranes should be unconnected Ribosomes should be drawn as filled in dots and labelled as 80S in size Mitochondria should be sausage-shaped and the inner membrane highly folded Peroxisomes, lysosomes and secretory vesicles should all look the same When drawing Plant cells, the following should be included A large central vacuole should be included that occupies significant space within the cell A cell wall made of cellulose should be included as a thicker line external to the plasma membrane Chloroplasts should be double-membrane structures with internal stacks of flattened discs Microscopes are scientific instruments that are used to visualize objects that are too small to see with the naked eye There are two main types of microscopes: 1. Light microscopes These microscopes use glass lenses to bend light in order to magnify images Light microscopes use visible light and a combination of lenses to magnify images of mounted specimens Most light microscopes include both an ocular lens and objective lens 2.Electron microscopes Electron microscopes can generate images at a much higher magnification and resolution, however, cannot view living specimens in natural color Calculating Magnification To calculate the linear magnification of a drawing or image, the following equation should be used Magnification = Image size ÷ Actual size In order to calculate magnification, both image size and actual size must be in the same units Metric conversions can be applied according to the following table Stem cells Stem cells are undifferentiated cells that can divide and differentiate into many different types of cell. Stem cells can be found in both plants and animals. In plants, stem cells are found in meristems (the tips of roots and shoots). In animals, stem cells can be found in different places including embryos, some adult cells such as hematopoietic cells (in bone marrow) and cord blood cells. Stem cells can be used for the treatment of many diseases such as leukemia, lymphoma and diabetes. Characteristics of Stem cells: 1. Self-renewal: They can continually divide and replicate 2. Potency: They have the capacity to differentiate into specific cell types Locations of stem cell niches in the human body include the bone marrow, hair follicles, heart, intestines and brain. Bone Marrow: Haemopoietic stem cells are located within the bone marrow and give rise to the different types of blood cells Bone marrow transplants are commonly employed to replace the haemopoietic stem cell niche following chemotherapy for leukemia Hair Follicles: The hair follicles contain a range of epidermal stem cells that are involved in hair growth & wound repair These stem cells could potentially be harvested and used to regenerate skin tissue in burns victims  Cell membrane Cell membrane function to enclose the contents of the cell, separating the intracellular components from the external environment This allows for the control of internal conditions within the cell and the maintenance of homeostasis Semi-permeability: Only certain materials are able to freely cross the cell membrane Selectivity: The cell can control the passage of any material that cannot freely cross the membrane Cell membranes are comprised of two main components: phospholipids and proteins: 1-Phospholipid Bilayer: The phospholipids form a bilayer that acts as a barrier to certain materials The hydrocarbon chains that form the core of the bilayer are hydrophobic and have low permeability to large and charged substances This means that large compounds and hydrophilic particles cannot cross the bilayer 2-Membrane Proteins: Membrane proteins embedded within the phospholipid bilayer may act as points of transport for large and charged substances This makes the lipid bilayer a selective barrier as the membrane proteins can coordinate the transport of hydrophilic materials according to need  Structure of Phospholipids Consist of a polar head composed of a glycerol and a phosphate molecule Consist of two non-polar tails composed of fatty acid chains Because phospholipids contain both hydrophilic and lipophilic regions Phospholipids spontaneously arrange into a bilayer The hydrophobic tail regions face inwards and are shielded from the surrounding polar fluids The two hydrophilic head regions face outwards and associate with the cytosolic and extracellular fluids respectively  Properties of the Bilayer The phospholipid bilayer is held together by weak hydrophobic interactions between the tails The presence of hydrophilic and hydrophobic layers restrict the passage of many substances Individual phospholipids can move within the bilayer, allowing for membrane fluidity and flexibility This fluidity allows for the spontaneous breaking and reforming of membranes  Movement of materials across a biological membrane Passive Transport: movement of material along a concentration gradient (high concentration ⇒ low concentration) 1. Simple diffusion: movement of small or lipophilic molecules that can freely cross the bilayer 2. Osmosis: movement of water molecules across the bilayer 3. Facilitated diffusion: movement of large or charged molecules via transmembrane proteins Active Transport: movement of materials against a concentration gradient (low concentration ⇒ high concentration) 1. Primary active transport: A molecule is moved against its gradient using energy from the hydrolysis of ATP 2. Secondary active transport: A molecule is moved against its gradient coupled to another molecule moving down an electrochemical gradient  Osmosis Special form of simple diffusion that involves the movement of free water molecules Water is a solvent capable of dissolving any polar or charged molecule to create a solution While water is a polar molecule, it is small enough to move between phospholipids in the bilayer Osmosis is the net movement of water molecules across a semi- permeable membrane from a region of low solute concentration to a region of high solute concentration Solutions may be loosely categorized as: “hypertonic, hypotonic or isotonic” according to their relative solute concentrations Solutions with relatively higher solute concentrations are categorised as ”Hypertonic” Solutions with relatively lower solute concentrations are categorised as ”Hypotonic”  Solutions that have equivalent solute concentrations are categorised as ”Isotonic” Video link showing the Red onion cell and its osmosis: https://www.youtube.com/watch?v=Iv7eGCPVaAk