GCSE Cells, tissues and organs

Movement - the ability of organisms to move( by the action of muscles in animals and slow growth movements in plants) Reproduction - the process that makes more of the same organism, producing offspring Sensitivity - the ability to detect and respond to changes in the internal and external environment (respond to stimuli) Control - organisms are able to control their internal conditions and maintain a steady state inside the body Growth - living things increases in size, mass and complexity. They also progress through different stages in their life cycle where their characteristics may change Respiration - a set of chemical reactions in our cells. Breakdown nutrient molecules and release energy for metabolism (release energy from food) Excretion - getting rid of waste products of metabolism. Removal of substances in excess of requirement Nutrition - taking in of materials for energy, growth and development (plants make their own food, animals eat other organisms)

Eukaryotic - have a nucleus, have membrane-bound organelles (enclosed in a membrane), DNA is in nucleus e.g. animals, plants, protoctists, Prokaryotic - have no nucleus, DNA is in cytoplasm e.g. bacteria

• These are multicellular organisms (made up of many cells) • Their cells contain chloroplasts and are able to carry out photosynthesis • Their cells have cellulose cell walls • They store carbohydrates as starch or sucrose • Examples include flowering plants, such as a cereal (for example, maize), and a herbaceous legume (for example, peas or beans).

• These are multicellular organisms • Their cells do not contain chloroplasts and are not able to carry out photosynthesis • They have no cell walls • They usually have nervous co-ordination and are able to move from one place to another • They often store carbohydrate as glycogen • Examples include mammals (for example, humans) and insects (for example, housefly and mosquito).

• these are organisms that are not able to carry out photosynthesis; • their body is usually organised into a mycelium made from thread-like structures called hyphae which contain many nuclei; • some examples are single-celled; • their cells have walls made of chitin; • they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition • they may store carbohydrate as glycogen. • Examples include Mucor, which has the typical fungal hyphal structure, and yeast, which is single-celled.

• These are microscopic single-celled organisms. • They are a mixed group of organisms that don’t fit into any of the other categories • Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. • A pathogenic example is Plasmodium, responsible for causing malaria.

• These are microscopic single-celled organisms • They have a cell wall, cell membrane, cytoplasm and plasmids • They lack a nucleus but contain a circular chromosome of DNA • Some bacteria can carry out photosynthesis but most feed off other living or dead organisms • Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia.

an organism that causes disease. These include fungi, protoctists and bacteria. It also includes viruses but viruses are non-living organisms.

• These are not living organisms. • They are small particles, smaller than bacteria • They are parasitic and can reproduce only inside living cells • They infect every type of living organism. • They have a wide variety of shapes and sizes • They have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA. • Examples include the tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes ‘flu’ and the HIV virus that causes AIDS.

Organelles->cells->tissues->organs->organ system Tissue - a group of similar cells that work together to carry out a particular function. They can contain more than one cell type. Organ - a group of different tissues that work together to perform a function Organ system - organs work together to form organ systems. Each system has a different function. Each system has a different job

• Nucleus - the nucleus controls the cell and has chromatin and DNA. The largest organelle in the cell. It contains chromosomes which carry the genetic material or genes. • Cytoplasm - like a thick, watery liquid and contains molecules like enzymes. It is where all of the reactions happen. The living material that makes up a cell is called the cytoplasm. • Cell membrane - the cell membrane surrounds the cell and controls what enters and exits the cell. It is a thin layer on the surface of the cell. It forms a boundary between the cytoplasm of the cell and the outside. • Cell wall - protects the cell and gives it its shape. It is a layer of non-living material that is found outside the cell membrane in plants • Mitochondria - it releases energy created during respiration • Chloroplasts - it contains chlorophyll that captures sunlight to be used for photosynthesis and creates glucose and oxygen. They are cells of the green parts of plants. • Ribosomes - the site of protein synthesis, the smallest organelle • Vacuole - contains SAP which contains minerals and ions. The SAP contains dissolved sugars, mineral ions and other solutes.

Animal has nucleus, mitochondria, ribosome, cell membrane, cytoplasm Plant has cell wall, chloroplast, SAP vacuole

• Cell differentiation is the process by which a cell changes to become specialised for its job • Undifferentiated cells (stem cells) can divide many times by mitosis without becoming differentiated, providing a stock of cells that can later become differentiated to provide the specialised cells that the body needs depending on the instructions that it is given • Cell differentiation is important in the development of specialised cells as it allows completely unspecialised cells to transform into specialised cells • In adult humans, stem cells have already started to specialise so they cannot make big repairs to their bodies e.g. a stem cell in the skin can only develop into a skin cell. Adults have them in bone marrow and skin. • It is important that all living things have cells that can divide by mitosis so they can repair, replace and grow differentiated cells. This enables the formation of tissues, organs and organ systems, allowing the organism to carry out complex processes efficiently • Specialisation enables cells to become more efficient at carrying out a particular job. Without differentiation, organisms could not develop the variety of cell types required for growth, repair, coordination and maintaining life. • In early development, the embryo contains unspecialised cells that later differentiate to form all the different cell types in the body

• Advantages ○ Stem cells from the patient won’t be rejected by the body ○ Can replace damaged or non-functioning cells ○ Adult stem cells can treat blood diseases if they come from the stem cells in bone marrow ○ Embryonic stem cells can form any cell type • Disadvantages ○ Ethical concerns as in order to obtain the embryonic stem cells, the embryo needs to be destroyed and some people view that as ending a potential human life. ○ Risk of immune rejection - the stem cells may be recognised as foreign leading to them being rejected ○ Risk of uncontrolled growth ○ Adult stem cells can only differentiate into a small range of cells so they are less versatile than embryonic stem cells