AQA Biology Topic 1 Higher

• • All living things are made from cells.
• • Cells can either be prokaryotic or eukaryotic. Eukaryotic cells are more complex whereas prokaryotic cells are smaller and simpler
• plant and animal cells contain the following subcellular structures: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
• the nucleus contains the genetic material and controls the cells activities
• The cytoplasm is where chemical reactions happen
• the cell membrane controls what goes in and out the cell
• mitochondria is where aerobic respiration takes place.
• ribosomes are where proteins are made in the cell
• Plant cells have extra structures that animal cells dont have which include: chloroplasts, cell walls, and permanent vacuoles
• the cell wall is made of cellulose and supports and strengthens the cell
• the vacuole contains cell sap
• chloroplasts are where photosynthesis occurs and they contain a green substance called chlorophyll
• Bacteria are examples of prokaryotes and they have no nucleus
• Light microscopes use light and lenses to form images
• the electron microscope is used to see the internal structures of cells and have a higher magnification and resolution
• magnification = image size / real size
• Differentiation is the process where a cell changes to become specialised for its job
• undifferentiated cells are called stem cells
• Sperm cells are specialised for reproduction and the function of a sperm is to get the male DNA to the female DNA. it has a long tail and streamlined head to help it swim to egg. It also contains digestive enzymes in the head to help break into the egg. It also contains mitochondria to provide energy for the swimming
• Nerve cells are specialised for rapid signalling. The function is to carry electrical signals from one part of the body to another. The cells are long to cover more distance and have branched connections to form networks
• Muscle cells are specialised for contraction. The function is to contract quickly and it has lots of mitochondria to generate the energy needed for contraction
• Chromosomes contain genetic information in the form of DNA
• we have 23 pairs of chromosomes and 46 in total
• embryonic stem cells can turn into any type of cell
• adults have stem cells but can only be found in bone marrow
• diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
• osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• root hairs take in water and minerals