Automatically Generated Summary: Cells
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Cells All forms of life are built of cells.
Compare the human cells and onion cells in Figure 1.9.
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4. DNA is a nucleic acid found in cells.
All organisms are made up of one or more cells, and all cells have many of the same structures and carry out the same basic life processes.
Based on whether they have a nucleus, there are two basic types of cells: prokaryotic cells and eukaryotic cells.
Leeuwenhoek's Discoveries Soon after Robert Hooke discovered cells in cork, Anton van Leeuwenhoek in Holland made other important discoveries using a microscope.
The Cell Theory By the early 1800s, scientists had observed the cells of many different organisms.
This relationship also applies to cells; a larger cell has less surface area relative to its volume than a smaller cell.
Vocabulary ATP cell wall central vacuole chloroplast cytoskeleton endoplasmic reticulum endosymbiotic theory Golgi apparatus mitochondria phospholipid bilayer vacuole vesicle Introduction Your body is made up of trillions of cells, but all of them perform the same basic life functions.
Vocabulary cytoplasm eukaryote eukaryotic cell nucleus organelle plasma membrane prokaryote prokaryotic cell ribosome virus Introduction If you look at living matter with a microscope—even a simple light microscope—you will see that it consists of cells.
Without this technology, we wouldn't be able to see the structures inside cells.
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In your body, glucose is the form of energy that is carried in your blood and taken up by each of your trillions of cells.
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These mutations may have little effect on the organism because they are confined to just one cell and its daughter cells.
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Figure 8.13: Sickle-Shaped and Normal Red Blood Cells.
However, human cells use splicing and other processes to make multiple proteins from the instructions encoded in a single gene.
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The human insulin gene was cloned and used to transform bacterial cells, which could then produce large quantities of human insulin.
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It allowed cells to use oxygen to obtain more energy from organic molecules.
One cell (or group of cells), called the last universal common ancestor (LUCA), gave rise to all subsequent life on Earth.
Photosynthesis and Cellular Respiration The earliest cells were probably heterotrophs.
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The First Eukaryotic Cells According to the endosymbiotic theory, the first eukaryotic cells evolved from a symbiotic relationship between two or more prokaryotic cells.
The other way is when cells directly exchange DNA (usually plasmids) with other cells.
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They also carry food (sugar dissolved in water) from photosynthetic cells to other cells in the plant for growth or storage.
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Dermal Tissue Dermal tissue covers the outside of a plant in a single layer of cells called the epidermis.
In the next chapter, you can read more about the special cells, tissues, and organs of plants that make them such important and successful organisms.
The key to continued growth and repair of plant cells is meristem.
www.ckl2.org Plant Cell Structures Structures found in plant cells but not animal cells include a large central vacuole, cell wall, and plastids such as chloroplasts.
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As the water flows by, specialized collar cells filter out food particles such as bacteria.
Table 17.2: Major Invertebrate Phyla Phylum (includes) Notable Characteristics Example Porifera (sponges) Cnidaria (jellyfish, corals) Platyhelminthes (flatworms, tapeworms, flukes) Nematoda (roundworms) Mollusca (snails, clams, squids) Annelida (earthworms, leeches, marine worms) Arthropoda (insects, spiders, crustaceans, centipedes) multicellularity, specialized cells sponges but no tissues, asymmetry, incomplete digestive system radial symmetry, true tissues, in- jellyfish complete digestive system cephalization, bilateral symme- flatworm try, mesoderm, complete digestive system pseudocoelom, complete diges- roundworm tive system true coelom, organ systems, some snail with primitive brain segmented body, primitive brain earthworm segmented body, jointed ap- insect (dragonfly) pendages, exoskeleton, brain www.ckl2.org Table 17.2: (continued) Phylum (includes) Notable Characteristics Example Echinodermata (sea stars, sea urchins, sand dollars, sea cucumbers) complete digestive system, coelom, spiny internal skeleton sea urchin Protostomes and Deuterostomes Most invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.
They grow from specialized cells in the body of the sponge.
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Cells The most basic parts of the human machine are cells—an amazing 100 trillion of them by the time the average person reaches adulthood!
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It supports the body, protects internal organs, produces blood cells, and maintains mineral homeostasis.
Muscles are organs composed mainly of muscle cells, which are also called muscle fibers.
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Blood vessels are part of the circulatory system, the "highway" system of the human body that transports materials to all of its cells.
However, each hormone affects only certain cells, called target cells.
Points to Consider In this lesson you learned that endocrine hormones can affect cells throughout the body because they travel in the blood through the circulatory system.
Sensory organs such as the eyes contain cells called sensory receptors that respond to particular sensory stimuli.
They are fat soluble, so they can diffuse across the plasma membrane of target cells and bind with receptors in the cytoplasm of the cell (see Figure 22.27).
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Figure 23.10: (Watch Youtube Video) http://www.ckl2.org/flexbook/embed/view/213 Blood Type Blood type is a genetic characteristic associated with the presence or absence of certain molecules, called antigens, on the surface of red blood cells.
Peripheral Gas Exchange The cells of the body have a much lower concentration of oxygen than does the oxygenated blood in the peripheral capillaries.
The exchange of gases and other substances between cells and the blood takes place across the extremely thin walls of capillaries.
Types of blood cells in plasma include red blood cells, white blood cells, and platelets (see Figure 23.8).
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Antigen Recognition B and T cells actually recognize and respond to antigens on pathogens.
Erythropoietin, for example, is a kidney hormone that stimulates bone marrow to produce red blood cells when more are needed.
Lymphocytes are the key cells involved in the immune response.
Memory Cells Most plasma cells live for just a few days, but some of them live much longer.
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3. How do plasma cells form, and how do they help fight pathogens?
4. Describe one way that cytotoxic T cells destroy cells infected with viruses.
Activated T cells destroy certain cancer cells and cells infected by viruses.
Active immunity results from an immune response to a pathogen and the formation of memory cells.
Memory T cells remain in the body after the immune response and provide antigen-specific immunity to the virus.
What if pathogens attacked and destroyed cells of the immune system itself?
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If you look inside the seminiferous tubule drawing shown in Figure 25.3, you can see cells in various stages of spermatogenesis.
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Because of this process, cells develop unique structures and abilities that suit them for their specialized functions.
Differentiation of Cells A zygote is a single cell.
Each layer will soon develop into different types of cells and tissues, as shown in Figure 25.12.
Organ Formation After cells differentiate, all the major organs begin to form during the remaining weeks of embryonic development.