Year 11 Human Biology Cells | PDF

Year 11 Units 1 &2 Human Biology CELLS Syllabus Statements Cells and tissues The human body is comprised of cells, tissues and organs within complex systems that work together to maintain life Cell organelles maintain life processes and require the input of materials an...

Year 11 Units 1 &2 Human Biology CELLS Syllabus Statements Cells and tissues The human body is comprised of cells, tissues and organs within complex systems that work together to maintain life Cell organelles maintain life processes and require the input of materials and the removal of wastes to support efficient functioning of the cell The cell membrane separates the cell from its surroundings with a structure, described by the fluid mosaic model, which allows for the movement of materials into and out of the cell by diffusion, facilitated diffusion, osmosis, active transport and vesicular transport (endocytosis/exocytosis) Factors affecting the exchange of materials across the cell membrane include surface area to volume ratio, concentration gradients, and the physical and chemical nature of the materials being exchanged The various tissues of the human body perform specific functions and can be categorised into four basic tissue types: epithelial, connective, muscular and nervous The Cell Theory The idea that all living things are composed of cells developed over many years and is strongly linked to the invention and refinement of the microscope. Three main principles All living things are made up of one or more cell. Cells are the basic unit of life. Cells come from other cells LEVELS OF ORGANISATION Cell Requirements Stable environment. Supply of nutrients, gases and other materials. Removal of wastes and other materials. Continual exchange of materials between the cell and the extracellular fluid. Oxygen for respiration. Cells are made up of the following Cell membrane: Surrounds and forms the outer boundary Cytoplasm: Fluid within and organelles Cytosol: Liquid part of the cell Organelles: Structures within the cell that carry out particular functions Cytoskeleton: internal scaffolding of protein fibres within the cell Inclusions: Chemical substances within the cell (granules or liquid droplets)  CELL STRUCTURE & FUNCTION Complete task Cells Chpt 2 à P27 CYTOPLASM CYTOSOL Structure The cytosol is the fluid component of the cytoplasm gel-like substance containing 75-90% water, ions, and various molecules like proteins and small molecules. Function: serves as the medium in which many chemical reactions occur (e.g., glycolysis) Helps transport materials between organelles provides a solution for the dissolved ions and nutrients that are used by the cell CYSTOSKELETON STRUCTURE is a network of protein filaments provide structural support to the cell located throughout the cytoplasm and is composed of three main types of filaments: Microtubules: Hollow tubes that help with cell shape, organelle movement, and cell division. Intermediate filaments: Provide mechanical support and maintain the cell's shape. Actin filaments: Involved in cell movement, shape changes, and muscle contraction. FUNCTION Helps cell maintain shape provides structural support & facilitates intracellular transport, essential for cell division and cell movement. Cytoplasm: The entire area inside the cell, including the cytosol, organelles, and cytoskeleton. Cytosol: The fluid component of the cytoplasm, where biochemical reactions occur. Cytoskeleton: The protein network that gives the cell its shape, structure, and aids in movement and division. Cell Membrane STRUCTURE Outer boundary of cell , separates adjacent cells Made of a phospholipid bilayer embedded proteins (integral and peripheral), cholesterol, and glycoproteins. FUNCTION Selective permeability: Controls the movement of substances in and out of the cell via certain mechanisms: - Diffusion - Osmosis - facilitated diffusion - active transport.  NUCLEUR MEMBRANE Nucleus STRUCTURE Double membrane, contains pores & Nucleolus FUNCTION allows selective passage of materials NUCLEUS STRUCTURE Separated from cytoplasm by nuclear membrane FUNCTION houses the DNA, which is responsible for storing genetic information and guiding cell activities like growth, reproduction, and repair. Transcription (the process of copying DNA into RNA) occurs here before the RNA moves to the cytoplasm for translation (protein synthesis). NUCLEOLUS STRUCTURE Located within the nucleus FUNCTION synthesizes rRNA and assembles ribosome subunits. Ribosomes STRUCTURE float freely in cytoplasm or attached to the endoplasmic reticulum (forming the rough ER FUNCTION responsible for protein synthesis. read messenger RNA (mRNA) and translate it into amino acid chains, forming proteins. They are essential for cellular function, growth, and repair 15  Ribosomes Role Inside nucleusà DNA contains full set of instructions (genes) for making proteins….can’t exit Passing instructions à DNA makes copy of code à mRNA form (Process=transcription) Transcription à DNA "unzips" à strand is used to create a complementary mRNA strand. mRNA leaves nucleus à nuclear pores à cytoplasm à ribosomes located. Ribosome will use the mRNA to build a protein. Endoplasmic Reticulum (ER) - Rough ER - Smooth ER Endoplasmic Reticulum (ER) Rough ER (Rough Endoplasmic Reticulum) Smooth ER (Smooth Endoplasmic Reticulum) Structure: Structure: network of membrane-bound sacs, studded with tubular network of membranes (no ribosomes) ribosomes (on cytoplasmic side). Function: Function: involved in lipid synthesis, including phospholipids responsible for protein (important for membrane structure) and steroid synthesis and modification. hormones. detoxification, especially in liver cells where it Ribosomes on its surface synthesize proteins that breaks down toxic substances like alcohol or drugs. are either storage and release of calcium ions, which is - secreted from the cell important for muscle contraction and other cellular signalling processes. - incorporated into the cell membrane - sent to an organelle called the Golgi apparatus for further modification. involved in the folding and quality control of proteins. Golgi Apparatus (Packaging and Shipping Centre) Golgi Apparatus (Packaging and Shipping Center) Structure: series of flattened, membrane-bound sacs (cisternae). closely connected to rough ER & receives proteins/lipids from it. Function: responsible for modifying, sorting, and packaging proteins and lipids for transport. It also produces lysosomes, which are involved in the breakdown of cellular waste. It adds carbohydrate tags to proteins (glycosylation) to help them reach their destinations. Lysosomes Structure: small, spherical membrane-bound organelles containing digestive enzymes. Function: break down/digest waste materials, cellular debris, and foreign substances (e.g., bacteria). key role in autophagy à process where the cell degrades its own components for recycling. fuse with vacuoles to digest material engulfed by the cell.  Mitochondria (Powerhouses of the Cell) Structure: oval-shaped, double-membraned organelles. Inner membrane à highly folded structures i.e cristae Contain own DNA and can replicate independently of the cell Function: sites of cellular respiration, process converts glucose and oxygen into ATP(adenosine triphosphate) primary energy carrier in the cell. ATP produced by mitochondria powers various cellular processes including -muscle contraction -protein synthesis -and active transport. Cell Membrane & Movement How Substances Get Into and Out of The Cell Each cell is surrounded by a cell/plasma membrane Extremely thin The cell membrane is selectively permeable It allows some substances to cross. The model for the cell membrane is known as the fluid mosaic model.  Fluid Mosaic Model Fluid because the molecules are constantly moving. Mosaic because it is made up of many different molecules. Cell Membrane The membrane is made of phospholipid molecules in a double layer à phospholipid bilayer 2 parts: Hydrophilic (water loving) head Hydrophobic (water hating) tail **Head on the outside, tail on the inside Cholesterol Embedded in the bilayer. Cholesterol molecules regulate the fluidity of the cell membrane which is necessary for the cell to retain it's shape. Are attracted to each other providing strength when required. Membrane Proteins Receptor proteins Receptors bind to signalling molecules. Determine cell response. Growth, hormone release, etc. Channel proteins Simple diffusion Carrier proteins Facilitated diffusion and active transport Cell identity markers  Functions of the Cell Membrane 1. Physical barrier 3. Sensitivity Separates cytoplasm and extracellular The cell membrane is the first fluid. part of the cell to be affected Important as cytoplasm and extracellular fluid have very different by change in extracellular fluid. composition. Receptors are sensitive to molecules in ECF. 2. Regulation of the passage of materials Semi-permeable membrane controls 4. Support the movement of substances into and out of cell. Cytoskeleton attached to the Water, Oxygen, Carbon Dioxide, cell membrane. Glucose. Transport Across the Cell Membrane Transport processes are either: Passive transport No energy required Active transport Uses energy (ATP) Transport Processes 1. Diffusion Passive Spreading of particles so that they are evenly distributed Osmosis – water diffusion 2. Carrier-mediated transport Passive or active Channel or Carrier Proteins required 3. Vesicular transport Active Transport in membrane bound sacks Diffusion Sspreading of particles (liquid or gas) until they are evenly distributed over available space. Results from the random motion of atoms and molecules due to their kinetic energy. As they move, they hit each other and bounce away. Molecules moving away from a concentrated area stay in straight lines longer and therefore move further away. The random movement continues even when evenly spread. Diffusion When the concentration of a substance is different at two places, the substance will diffuse along the concentration gradient until the concentration of the two areas becomes equal. Diffusion Alcohol, steroids and other fat soluble substances enter the cell via diffusion. Oxygen diffuses with the concentration gradient into the cell and is used in cellular respiration. Carbon dioxide diffuses with the concentration out of the cell. 35  Concentration Concentration at A at B 1 Diffusion High gradient concentration Low concentration R a te o f d if f u s io 2 n s lo ws Equilibrium 3 Uniform concentration Osmosis Diffusion of a solvent (water) through a differentially permeable membrane. Moves from a region of high solvent concentration to low concentration/low solute concentration to high. Where there is more solute there will be less solvent. Passive process Glucose and ions such as sodium unable to enter through diffusion. Water can fit between lipid tails or through protein channels. Protein Channels Water soluble molecules like certain drugs and vitamins are repelled by the hydrophobic inner portion of the cell membrane. Protein channels provide a pathway for these hydrophilic substances to pass into the cell. Large molecules cant fit through the protein channels. 39 Facilitated Transport Proteins in the cell membrane allow molecules to be transported across the membrane. Channel proteins act like pores to allow substances like water, ions and glucose. Carrier proteins are involved in carrier mediated transport. Sodium Potassium pump. 40  Carrier Proteins Carrier Proteins in the cell membrane that are only open to one side of the membrane at a time bind to protein molecules to be transported across the membrane. When the specific substance binds to the binding site the protein changes shape, opens to other side of membrane and releases the substance. Characteristics: Specific – only bind to a particular molecule Can become saturated – if no free carrier molecules, no more will be transported Regulated by substances such as hormones Carrier Mediated Transport 1. Facilitated diffusion Passive process using proteins – from high to low Examples: glucose & amino acids 2. Active transport Requires energy – against the concentration gradient (from low to high) Does not rely on concentration gradient, Example: membrane pumps Active Transport (sodium pump) Diagram created by LadyofHats VESICULAR TRANSPORT Vesicular Transport Movement of substances using vesicles Active process Endocytosis = things entering the cell Phagocytosis = cell eating (take in solids) Pinocytosis = cell drinking (take in water) Exocytosis = things leaving the cell Endocytosis Cell membrane folds around a droplet. Vesicle is formed and pinched off when droplet is completely enclosed. Vesicle is suspended in the cytoplasm of the cell. 46 Exocytosis Vesicle is formed inside the cell. Migrates the to the cell membrane and fuses with it. Contents of the vesicle are then pushed out into the extracellular fluid. 47 Transport Within Cell Substances within cell mostly move via diffusion. Think about oxygen and the mitochondria. Endoplasmic reticulum transports substances like proteins to the Golgi Body. Microtubules act like railway tracks guiding organelles and molecules within cell. 48 SLIDE 49-70