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Cell Structure and Function. Levels of Organization. Organism. Organ System. Organ. Tissues. Organelles. Cells. Cells. A cell is the smallest unit that is capable of performing all 8 life functions . MRS C GREN. Cells. The size & shape of a cell relates to its function.
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Cell Structure and Function
Levels of Organization Organism Organ System Organ Tissues Organelles Cells
Cells • A cell is the smallest unit that is capable of performing all 8 life functions. • MRS C GREN
Cells • The size & shape of a cell relates to its function. • Two main types of cells: • Prokaryotic • Eukaryotic
Prokaryotic Cells • Cells that lack a cell nucleus, or any other membrane-bound organelles. • Chromosome is a simple DNA chain with the ends joined to form a circle.
Prokaryotic Cells • Most are unicellular, but some prokaryotes are multicellular. • E.g . bacteria, blue-green algae
Eukaryotic Cells • Higher organisms whose cells are arranged into complex structures enclosed within membranes. • The chromosome is a length of DNA folded. It is wound around proteins. • E.g. Animals, plants, fungi and protists.
Organelles • No plant or animal cells are alike but they do share some common organelles.
Cell Membrane • All cells are separated from their environment by a cell membrane. • For cells with cell walls, the membrane is inside the cell wall.
Cell Membrane • Consists of two layers of lipids (lipid bilayer). • One lipid includes a hydrophilic (water-loving) head and hydrophobic (water-hating) tails.
Lipid Lipid Bi-layer Cell Membrane
Semi-Permeable Membrane • Proteins in the membrane allow nutrients, oxygen, and water into the cell and waste products out of the cell. • These proteins also limit other molecules from entering or leaving the cell.
Protein Gate Lipid Lipid
Cytoplasm • Cytoplasm is the semi-fluid solution found inside the cells. • It contains dissolved substances, enzymes and all other cell organelles.
Cytoskeleton • Scaffolding-like structure made of protein found in cytoplasm. • Helps the cell maintain or change its shape.
Nucleus • Usually the largest organelle the nucleus contains genetic material that directs all cell activities. • Separated from the rest of the cell by a nuclear membrane. Nucleus Pores Nuclear Membrane Nucleolus
Nucleus • Made up of three parts: • Nuclear envelope – a double membrane covering that controls the entry and exit of the large molecules and particles that need to go in and out.
Nucleus • Genetic Material – In a resting cell the DNA is unravelled (chromatin) and too small to be seen. When a cell is about to divide the DNA coils, thickens and can be seen (chromosomes).
Nucleus • Nucleolus – The main function of the nucleolus is the production and assembly of ribosome components (RNA, proteins).
Endoplasmic Reticulum (ER) • Continuous with the cell membrane and the nuclear envelope. • The ER is a series of membranes and connecting tubes that provide a work surface for chemical reactions as well as a passageway for moving materials around the cell.
Endoplasmic Reticulum (ER) • There are two types or ER: • Smooth ER • Rough ER (ribosomes attached)
Ribosomes • Found either bound to the ER or free floating within the cytoplasm. • Site where proteins are made (protein synthesis).
Ribosomes • Free ribosomes make proteins to be used in the cell. • The ribosomes bound to the ER make proteins to be secreted by the cell.
Golgi Bodies/Apparatus • A series of flattened sacs found in the cytoplasm. • The primary function is to process and package the macromolecules such as proteins and lipids that are synthesized by the cell.
Lysosomes • Tough, membranous bags containing digestive enzymes. • They digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria.
Vacuoles • Vacuoles are membrane-bound compartments that can serve a variety of storage functions. • They often contain water, food or wastes.
Vacuoles Video • In animal cells food vacuoles engulf food where it is digested by the lysosome's enzymes. • In plants it acts as a storage, a fluid skeleton and it also hold colour and poisons. • In unicellular organisms contractile vacuoles pump water out of the cells.
Contractile Vacuoles • These specialized vacuoles pump excess water out of a cell and is found prominently in freshwater protists.
Mitochondria • Converts energy from food into a form that a cell can use, called ATP. • It is the site of aerobic respiration. A cell with a large energy requirement will have lots of mitochondria.
Mitochondria • It has its own circular DNA, ribosomes and transfer RNA and protein making machinery. • In the matrix the krebs cycle takes place. • The electron transport chain takes place in the cristae.
Cell Wall • Found in plant cells, algae and most bacteria. • Made of cellulose to provide strength and shape.
Chloroplasts • Found in the cytoplasm of plants. • Function is to manufacture glucose through photosynthesis. • Contains the green pigment chlorophyll.
Chloroplasts • Made of thylakoid discs arranged in stacks called grana.
Centrioles • Found in all animal cells and most unicellular organisms. • During cell division, the centriole pair extends to form spindles to move chromosomes apart.
Cilia and Flagella • Found in some animal cells and unicellular organisms. • Both are cellular projections and are almost identical in structure, although cilia are shorter and often more numerous. • Many cells that line surfaces within our bodies are ciliated.
Cilia and Flagella • Both are often associated with movement.
Eyes Spots • Photoreceptive organelle found in green algae and other unicellular photosynthetic organisms. • It allows the cells to sense light direction and intensity and respond to it by swimming either towards or away from the light.
Eye Spots • This helps the cells in finding an environment with optimal light conditions for photosynthesis. • Eyespots are the simplest and most common "eyes" found in nature.
