Biology: Specialized Cells and Transport PDF

# Required Practical ## Microscopy Required Practical - Includes preparing a slide, using a light microscope, drawing any observations - use a pencil and label important observations. ### Microscope Diagram - Stage - Stage clips - Eyepiece - Objective lens - Light - Focusing wheels ## Osmosis...

# Required Practical ## Microscopy Required Practical - Includes preparing a slide, using a light microscope, drawing any observations - use a pencil and label important observations. ### Microscope Diagram - Stage - Stage clips - Eyepiece - Objective lens - Light - Focusing wheels ## Osmosis and Potato Practical - **Independent variable** - concentration - **Dependent variable** - change in mass - **Control variable** - volume of solution, temperature, time - **Constant set-up** - solutions, water, and time will have to remain the same. The potato in the sugar solution will lose water and so will have less mass at the end, the potato in the pure water solution will gain mass. ## Specialised Cells When a cell changes to become a specialised cell, it is called **differentiation**. | Specialised Cell | Function | Adaptations | |:---|:---|:---| | Sperm | To get the male DNA to the female egg. | Streamlined head, long tail, lots of mitochondria to provide energy | | Nerve | To send electrical impulses around the body. | Long to cover more distance, many branched connections on its end, as a network. | | Muscle | To contract quickly. | Long and contains lots of mitochondria for energy. | | Root hair | To absorb water from the soil | A large surface area to absorb more water | | Phloem | Transports manufactured nutrients around the plant | Pores to allow cell sap to flow through. Cells are long and lined up end to end. | | Xylem | Transports water around the plant through the plant | Hollow in the centre. Tubes are joined end to end. | ## Equations and Maths - **Image size** / **Actual size** = **Magnification** - **Micrometers to millimetres**, divide by 2000 - **Standard Form** - 0.001 = 1 × 10^-3 - 1.5 × 10^-3 = 0.0015 ## Prokaryotic and Eukaryotic Cells - **Animal Cells** Diagram - Nucleus - Cytoplasm - Mitochondria - Cell membrane - **Plant Cells** Diagram - Nucleus - Cell membrane - Cytoplasm - Mitochondria - Ribosomes - Cell wall - Chloroplast ### Plant and animal cells have similarities and differences: | | Animal | Plant | |:---|:---|:---| | Nucleus | ✓ | ✓ | | Cytoplasm | ✓ | ✓ | | Chloroplast | X | ✓ | | Cell Membrane | ✓ | ✓ | | Permanent vacuole | X | ✓ | | Mitochondria | ✓ | ✓ | | Ribosomes | ✓ | ✓ | | Cell wall | X | ✓ | ## Bacterial cells Bacterial cells do not have a true nucleus, they just have a single strand of DNA that floats in the cytoplasm, they contain a plasmid. - Diagram of a bacterial cell - Cell membrane - Cytoplasm - Plasmid - DNA - Cell wall - Flagella ## Chromosomes and Mitosis In the nucleus of a human cell there are 46 chromosomes, 23 pairs of homologous chromosomes. Chromosomes are made of DNA. Chromosomes have a large number of genes. - Diagram of chromosomes - 2 chromosomes are replicated before the cell carries out mitosis ## Stem Cells - **Embryonic stem cells** are **undifferentiated**, this means they have the potential to turn into any kind of cell. - **Adult stem cells** are found in the tissues of an adult. They can only turn into some types of cells e.g blood cells. ### Roles of stem cells - Replacing faulty blood cells - Making nerve cells - Making new skin cells ### Stem cells are against stem cell research. | For stem cell research | Against stem cell research | |:---|:---| | Curing patients with stem cells more important than the rights of embryos. | Embryos are humans lives. | | They are improving attenuated viruses from human cells, which would normally be deadly | Scientists should focus on other sources of stem cells | | They are potentially able to grow crops with specific features for a farmer e.g disease resistant | | ## Stem Cells in Plants In plants, stem cells are found in the meristem tissue of the plant. They can be used to produce clones of the plant. They are able to grow crops with specific features for a farmer e.g disease resistant. ## Exchange - Humans **Multicellular organisms** have a large surface area to volume ratio so that all the substances can be exchanged. - The alveoli are where gas exchange takes place. - They have a large surface area, moist lining, thin walls, and a good blood supply. - Diagram of the alveoli in the lungs. ### Villi, Small Intestine - **Villi** in the small intestine increase the surface area ratio to absorb more digested food. - They are a single layer of cells with a good blood supply. ## Exchange in Plants - The surface of the leaf is flattened to increase the surface area for gas and water vapour diffusion. - **Oxygen** and **moisture vapour** diffuse out of the stomata. Guard cells open and close the stomata, controlling water loss. - Diagram of the leaf ## Key Processes ### Diffusion - **Diffusion** is the spreading out of particles from an area of higher concentration to an area of lower concentration. - **Cell membranes** are semi permeable, some molecules can get through. ### Cell Diffusion - **Osmosis** is the movement of water molecules across a partially permeable membrane from a region of higher concentration to a region of lower concentration. - **Active transport** is the movement of substances against the concentration gradient. This process requires energy from respiration ### Active Transport in Cells - Diagram ## Exchange in Fish - Fish have a large surface area for gas exchange. These are called **gills**. - Water enters the fish through the mouth and goes out through the gills. The oxygen is transported from the water in the water by **diffusion** to **Gill filaments** which protrude into the water. Each gill has **Gill lamellae** which give the gill a large surface area. Lamellae are even more flattened to further increase surface area for more gas exchange. They have a **thin surface layer** and **capillaries** for good blood supply when water diffuses. - Diagram of gills