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Discover the fascinating world of cells, the smallest units of life with unique organelles that perform vital functions to keep organisms alive. Learn about the discovery and cell theory, types of cells, and essential components like cell membrane, nucleus, mitochondria, chloroplast, and more. Uncover the roles of ribosomes, vacuoles, cytoplasm, and other organelles in maintaining cellular processes. Dive into the intricate world of cell biology in this educational overview.
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Unit 3 Obj. 1.1.1, 1.1.2 Cell Structure
Place an “X” next to the things you think are made of cells • ___ flowers ___ hamburger ___ leaf • ___ skin ___ DNA ___ seeds • ___ proteins ___ calcium ___ water • ___ rocks ___ apples ___ sugar • ___ milk ___ sand ___ blood • ___ bone ___ worms ___ saliva • ___ lungs ___ bacteria ___ mushroom
What is a cell? • The smallest unit of life; the smallest thing biologists study • RECALL: Organization of Living Things: • Cell Tissue Organ Organ system Organism
What is a cell? • Cells have smaller parts inside of them called organelles • This means “little organ.” They perform special functions for the cell to keep it (and the organism) alive.
What is a cell? • Cells were discovered in 1665 by Robert Hooke • He thought they looked like the rooms monks lived in, so he called them “cells”
What is a cell? • Anton van Leeuwenhoek was the first to see living cells. He used a hand held microscope to look at pond scum and scrapings from his teeth in 1673. • He thought they look like little animals.
Cell Theory • Contributed to by Theodor Schwann and Matthias JakobSchleiden in 1839 and Rudolf Virchow in 1858. • Three main ideas: • 1. All living things are made of one or more cells. • Unicellular = one-celled organism • Multicellular = organism made from many cells • 2. Cells are the basic unit of structure and function in all living things. • 3. All new cells come from pre-existing cells.
Types of cells • 1. Prokaryotic (means “before nucleus”) • No nucleus, unbound DNA • No membrane-bound organelles • Small and simple; “older” type of cell • Examples: Bacteria • 2. Eukaryotic (means “true nucleus”) • Has a nucleus, DNA is inside nucleus • Has organelles • Larger and more complex; “younger” type of cell • Examples: Plants and Animals
Cell Membrane • Aka “plasma membrane” • Provides protection, helps cell communicate, transports substances in and out of cell, keeps the cell together • Made of a phospholipidbilayer (phosphate head, lipid tail, two layers) • The head is hydrophilic (loves water), the tails are hydrophobic (fears water) • Selectively permeable • Found in all cells
Cell Wall • Only found in plant cells • Shapes and supports the cell • Provides additional protection • Made of cellulose = humans cannot digest
Nucleus • Contains the genes that control the cell = DNA • Chromatin = uncoiled DNA • Chromosomes = coiled DNA • Surrounded by nuclear envelope = double membrane • The “information center” of the cell
Nucleolus • Makes rRNA and assembles ribosomes • Not surrounded by a membrane • Cells can have 1-3 • Disappears when the cell divides
Mitochondria • Where the cell performs respiration makes ATP, a molecule the cell can use as energy for work • Major site of metabolism • Folded inner membrane (cristae) more surface area for chemical reactions
Chloroplast • Found only in plant cells • Contains chlorophyll = pigment that gives plants their green color • Traps sunlight to make glucose (food) • Site of photosynthesis
Ribosomes • Protein synthesis = making proteins using RNA from the nucleus to assemble amino acids into proteins • Can be floating in cytoplasm or attached to a membrane
Vacuole • Stores water, sugar, salts, nutrients, wastes, etc. • Large and central in plant cells • Small or not present in animal cells
Cytoplasm • Jelly-like substance that helps fill up the cell and suspend organelles • Site of many metabolic reactions
Centriole • Only found in animal cells • Made of microtubules • Help the cell divide
Golgi Apparatus • Processes and packages macromolecules that are synthesized by the cell in vesicles (membrane bound packages) • Secretion • Found in eukaryotes only
Rough endoplasmic reticulum • Rough ER • Called “rough” because it is studded with ribosomes • Makes proteins • The “highway” of the cell transports proteins
Smooth endoplasmic reticulum • Smooth ER • Lacks ribosomes • Makes lipids • Also the “highway” of the cell an interconnected network of tubules and vesicles
Cytoskeleton • Made of protein – microtubules and microfilaments • “Framework” of cell • Provides structural support
Lysosomes • Contain digestive enzymes • Digest food, worn out organelles, viruses, etc. • Can also act as a “self-destruct button” and cause the cell to lyse itself apoptosis • The “janitor,” “hit man,” and “suicide bomber” of the cell
Flagellum • Tail-like projection from cell • Helps cell move by whipping around in a circle similar to helicopter blade
Cilia • Small, hair-like projections • Used to help cell move and sense environment
Pseudopodia • “False foot” • Temporary projections of eukaryotic cells • Usually found in amoeba • Cells use extension and contraction to move around
Plasmid • DNA molecule that is separate from and can replicate independently from chromosomal DNA • Usually found in prokaryotes
Eyespots • Photoreceptive organelle = can sense light • Usually found in unicellular photosynthetic cells, like green algae • Allows the organism to respond to light and swim towards it or away from it
To be or not to be… multicellular • What are some advantages? • Differentiation • More control over internal conditions • Greater motility able to move around and avoid predators and find more food • Genetic diversity greater chance for positive traits • What are some disadvantages? • Harder to reproduce must find a mate first • Need more resources
Cell Specialization • When cells have different jobs or functions • Only multicellular organisms can have specialized cells
Specialized Animal Cells • Muscle, bone, brain, nerve, skin, hair= all different cells with different functions • Muscle cells: have more mitochondria than other cells= more metabolism! • Cool fact: Muscle cells have more than one nucleus! • Red Blood Cells: lose their nucleus and are donut-shaped to carry oxygen molecules • Remember: Hemoglobin is a protein
How do you get specialized cells? • Start as a stem cell= has the ability to become any cell in the body a “blank slate” • Gets signals (usually hormones) to become a certain cell type (this is called differentiation)
Cell Communication - Chemical • Hormones = proteins that are used by both plant and animal cells to send messages • Produced in large amounts, usually in response to something environmental • Travel slowlythroughout the organism • Endocrine system (thyroid, testes, ovaries, pituitary gland, etc.) releases hormones into the blood stream • Affects only those cells with the right receptors= has effects on certain cells in the body
Cell Communication - Electrical • Neurons = cells in the nervous system that transmit information throughout the body. Animals only! • Sends messages that can be voluntary or involuntary • Send out neurotransmittersthat get passed from neuron to neuron • Neurons have two main parts: dendriteand axon