Cells
Cells The basic unit of life Microscopic Organelles Two types Structures within cells that perform different functions but work together Two types Animal cells Plant cells
Animal Cell
Plant Cell
Organelles in Animal Cells Cell membrane Made of proteins and lipids Thin, partially permeable Controls exchange of substances in cell Protects organelles Cytoplasm Made of water and dissolved substances Present throughout the cell Provides nutrients, glycogen granules Site of chemical reactions Nucleus Controls cell activities Contains genetic material or DNA in chromosomes
Organelles in Animal Cells Mitochondrion Pleated membrane to increase surface area Contains respiratory enzymes Produces energy through respiration Vacuole Fluid-filled membranes Small, temporary with no fixed shape Exchange of water, minerals and stores substances including waste Endoplasmic Reticulum Several membranes Make fats and proteins Contain ribosomes that make proteins
Organelles in Plant Cells Only Plant cells contain all the organelles that Animal cells contain in addition to these: Cell wall Freely permeable Made of cellulose Outside cell membrane Give shape and protects cell Chloroplast Contain green chlorophyll and enzymes Site of photosynthesis
Organelles in Plant Cells Only Starch grains Stores carbohydrates Vacuole Large, permanent with fixed shape Contains cell sap Supports cell when turgid Stores cell waste Cytoplasm A thin layer
Specialization Unicellular organisms made of one cell Independent of other cells One cell carries out functions Multicellular organisms made of many cells Each cell does a different job All work together and depend on each other
Specialization Division of Labour Allows organism to increase in size Higher productivity and efficiency Develop special features to carry out specific functions Different functions can be performed at the same time
Similar or identical cells that perform a specific function are arranged in groups to form tissues Cell Tissues
Several different kinds of tissues are grouped to form an organ Tissue Organ
Organs form larger functional units called systems Organ System
Systems are grouped to form an organism System Organism
Bacteria Unicellular Microscopic Release toxins Not all harmful Cause diseases Tuberculosis Typhoid Cholera
Viruses Unicellular (smaller than bacteria) Need other organisms to live Reproduce only inside living cells Enter body through openings Attach to then enter host cell Use the host cell to copy itself New viruses destroy and leave the host cell and attack new host cells All are harmful and cause diseases Common cold Influenza AIDS Measles
Fungi Very small (yeast) or large (mushrooms) Do not cause many diseases Athlelte’s foot Ringworm
Fungi cell
Cells of the human body
Reactions in Cells
Osmosis Movement of water particles from an area of high water concentration to an area of low water concentration across a selectively permeable membrane.
Diffusion Movement of molecules from a region of high concentration to a low concentration In gases and liquids Can occur across thin, permeable membranes End- products of digestion diffuse from gut into blood Carbon dioxide and Oxygen diffuse between blood and alveoli Between blood and cells Characteristics of surfaces for efficient diffusion Thin Concentration gradient Moist Large surface area to volume ratio
Importance of Diffusion and Osmosis To bring useful substances to organelles for reactions to take place Glucose and Oxygen in Respiration Removal of waste products Carbon dioxide from respiration, urea These are secreted out of the cell Small vessicles transport substances Hormones are transported this way
Active Transport Transport of molecules across a membrane from a region of lower concentration to a region of higher concentration, using energy. Allows cells to take up extra substances already present in its cytoplasm .e.g liver and glucose Allows cell to remove extra substances present in the cytoplasm.