Additional Science Biology

Cells and Simple Cell Transport:Cells:All living things are made up of cells. The structures of different types of cells are related to their functions.Root hair cells: Tiny like hair extensions that increase the surface area of the cell for absorption.Ovum (egg cell): Large cell that can carry food reserves for the developing embryo.Xylem: Long, thin, hallow cells used to transport water through the stem and root.White Blood Cells: Can change shape in order to engulf and destroy invading microorganisms.Sperm Cells: Has a tail, which allows it to move.Palisade Cells: packed with chloroplasts for photosynthesis.Red Blood Cells: No nucleus, so packed full of haemoglobin to absorb oxygen.Nerve Cells: Long, slender axons that can carry nerve impulses.Cell Structure:Most human cells, animal cells and plant cells have the following parts:Nucleus: Contains genetic material, which controls the activities of the cell.Cytoplasm: Most chemical processes take place here, controlled by enzymes.A Cell Membrane: Controls the movement of substances into and out of the cell.Mitochondria: Most energy is released by respiration here.Ribosomes: Protein synthesis happens here.Chemical reactions inside cells are controlled by enzymes found in the cytoplasm and mitochondria.Plant Cells:A cell wall: Used to strengthen the cell.Chloroplasts: Absorb light energy to make food.A permanent Vacuole: Filled with cell sap.Other Cells:In a bacterial cell, the genes are not in a nucleus.A bacterial cell consists of: Cytoplasm, a cell membrane and a cell wall.Yeast is a single celled fungus. Yeast cells have: Nucleus, Cytoplasm, Cell membrane and Cell wall.Movement of Substances:Cells have to constantly: Replace substances that are used up, e:g: glucose and oxygen for respiration.Remove other substances, e:g: carbon dioxide and waste products.Gases and substances that are in solution can pass into ad out of cells, through the cell membrane, by diffusion.Diffusion:Diffusion is the spreading of the particles of a gas or a substance in solution. It results in a net movement from a region where the particles are of a higher concentration to a region where they are of a lower concentration. The greater the difference in concentration, the faster the rate of diffusion.Tissues, Organs and Organ Systems.Tissues:Large multicellular organisms, like humans, develop systems for exchanging materials. As the organism develops, cells differentiate so that they can carry out different jobs.A tissue is a group of cells that have a similar structure and function. For example: Muscle tissue contracts so we can move. Glandular tissue produce substances such as enzymes and hormones. Epithelial tissue covers organs.Organs:Organs are made of tissues. One organ may contain several tissues.For example, the stomach is an organ that contains:Muscle tissue that contracts to churn the contents.Glandular tissue to produce digestive juices.Epithelial tissue to cover the outside and inside of the stomach.

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