Chapter 3: Cells and Their Functions

Overview

Key Terms active transport filtration mitochondria cancer gene mitosis carcinogen hemolysis mutation chromosome hypertonic nucleus cytology hypotonic organelle cytoplasm interphase osmosis diffusion isotonic phagocytosis DNA membrane potential plasma membrane endocytosis micrometer ribosome exocytosis microscope RNA

The Cell Cytology The study of cells The Cell The basic unit of life Shows life characteristics Organization Homeostasis Metabolism Growth Responsiveness Reproduction

Microscopes Learning Outcomes List three types of microscopes used to study cells.

Microscopes Cytology The study of cells Microscope An instrument that magnifies structures not visible with the naked eye Types of microscopes: Compound light microscope Transmission electron microscope Scanning electron microscope

Figure 3-1 Cilia photographed under three different microscopes. Answer: 3-1 The transmission electron microscope (B) shows the most internal structure. The scanning electron microscope (C) shows the cilia in three dimensions. Which microscope shows the most internal structure of the cilia? Which shows the cilia in three dimensions?

✓ Microscopes Checkpoints 3-1 What characteristics of life does a cell show? 3-2 Name three types of microscopes. Answers: 3-1 The cell shows organization, metabolism, responsiveness, homeostasis, growth, and reproduction. 3-2 Three types of microscopes are the compound light microscope, transmission electron microscope (TEM), and scanning electron microscope (SEM).

? Microscopes Pop Quiz 3.1 Which microscope is most commonly used in laboratories? Scanning electron microscope Transmission electron microscope Compound light microscope Simple light microscope

? Microscopes Pop Quiz Answer 3.1 Which microscope is most commonly used in laboratories? Scanning electron microscope Transmission electron microscope Compound light microscope Simple light microscope

Microscopes

Cell Structure Learning Outcomes Describe the composition and functions of the plasma membrane. Describe the cytoplasm of the cell, including the name and function of the main organelles.

Cell Structure General Cell Organization Plasma membrane Nucleus Cytoplasm Cytosol Organelles

Figure 3-2 A generalized animal cell, sectional view. Answer: 3-2 Ribosomes attached to the ER make it look rough. Cytosol is the liquid part of the cytoplasm. What is attached to the ER to make it look rough? What is the liquid part of the cytoplasm called?

Cell Structure Plasma Membrane Encloses cell contents Regulates what enters and leaves cell Participates in many cell activities (e.g., growth, reproduction, cell-to-cell interactions) Plasma membrane components Phospholipid bilayer Cholesterol Proteins

Cell Structure Table 3-1 Proteins in the plasma membrane and their functions. Type of Protein Function Channels Pores in membrane that allow passage of specific substances Transporters Shuttle substances across membrane Receptors Allow for attachment of substances to membrane; used for cell-to-cell signaling Enzymes Participate in chemical reactions at membrane surface Linkers Give structure to membrane and attach cells to other cells Cell identity markers Proteins unique to a person’s cells; important for immunity

Figure 3-3 The plasma membrane. Answer: 3-3 The plasma membrane is described as a bilayer because it is in two layers. Why is the plasma membrane described as a bilayer?

Cell Structure

Cell Structure Plasma Membrane Membrane potential The difference in electric charge on either side of the plasma membrane Caused by separation of positive and negative ions and proteins on either side of the membrane Ion concentrations are determined by Channels Pumps Membrane potential allows the plasma membrane to act as a battery. It uses electrical energy to power membrane functions.

Figure 3-4 The membrane potential. Answer: 3-4 Large, negatively charged protein ions contribute to the negative charge along the intracellular membrane. What large, negatively charged ions contribute to the negative charge along the intracellular membrane?

Cell Structure Nucleus Largest organelle of cell Surrounded by nuclear membrane Contains Chromosomes Units of heredity; govern all cellular activity Nucleolus Assembles ribosomes

Cell Structure Material between nuclear membrane and plasma membrane Cytoplasm Material between nuclear membrane and plasma membrane Cytosol Fluid portion of cytoplasm Organelles Specialized cell structures that perform different cell functions

Cell Structure Table 3-2 Cell parts (cytoplasmic organelles). Name Description Function Endoplasmic reticulum (ER) Membranous network; rough ER has ribosomes; smooth ER does not Rough ER sorts and modifies proteins; smooth ER synthesizes lipids Ribosomes Small bodies in cytoplasm or attached to rough ER Manufacture proteins Mitochondria Large bodies with internal folded membranes Manufacture ATP Golgi apparatus Layers of membranous sacs Prepares proteins for export Lysosomes, Peroxisomes Small sacs of enzymes Digest intracellular substances Vesicles Small storage sacs Store materials; move materials into or out of cell Centrioles Rod-shaped bodies near nucleus Help separate chromosomes during cell division

Cell Structure Surface Projections Structures that extend from the cell Cilia Short, hairlike projections Move fluids around cells Flagellum Long, whiplike extension from the cell Moves cell

Cell Structure Cellular Diversity Cell shape is related to cell function. A neuron’s long fibers transmit electric energy from place to place in the nervous system. Small round red blood cells slide through tiny blood vessels. Cell organelle number is related to cell function. Lipid-producing cells have lots of smooth ER. Metabolically active cells have lots of mitochondria to manufacture ATP.

Figure 3-5 Cellular diversity. Answer: 3-5 Epithelial cells (B) would best cover a large surface area because they are flat. Which of the cells shown would best cover a large surface area?

✓ Cell Structure Checkpoints 3-3 What is the main substance of the plasma membrane, and what are the three types of materials found within the membrane? 3-4 What is the membrane potential, and what types of substances maintain the membrane potential? 3-5 What are cell organelles? 3-6 Why is the nucleus called the cell’s control center? 3-7 What are the two types of organelles used for movement, and what do they look like? Answers: 3-3 The main substance of the plasma membrane is phospholipids. The three types of materials found within the membrane are cholesterol, carbohydrates (glycoproteins and glycolipids), and proteins. 3-4 The membrane potential is an electric charge (voltage differential) on the membrane. It is maintained by ions on either side of the membrane. 3-5 The cell organelles are specialized structures that perform different tasks. 3-6 The nucleus is called the cell’s control center because it contains chromosomes, hereditary units that control all cellular activities. 3-7 The two types of organelles used for movement are cilia, which are small and hairlike, and the fl agellum, which is long and whiplike

? Cell Structure Pop Quiz 3.2 What is the main substance of the plasma membrane? Cholesterol Phospholipid Protein Steroid

? Cell Structure Pop Quiz Answer 3.2 What is the main substance of the plasma membrane? Cholesterol Phospholipid Protein Steroid

? Cell Structure Pop Quiz 3.3 Which organelle generates ATP? Centriole Golgi apparatus Mitochondrion Ribosome

? Cell Structure Pop Quiz Answer 3.3 Which organelle generates ATP? Centriole Golgi apparatus Mitochondrion Ribosome

Movement of Substances Across the Plasma Membrane Learning Outcomes Describe methods by which substances enter and leave cells that do not require cellular energy. Describe methods by which substances enter and leave cells that require cellular energy. Explain what will happen if cells are placed in solutions with concentrations the same as or different from those of the cell fluids.

Movement of Substances Across the Plasma Membrane Selective Permeability Plasma membrane regulates what enters and leaves Travel across membrane is based on several factors Molecular size Solubility Electrical charge Types of travel Movement that does not require cellular energy Movement that requires cellular energy

Movement of Substances Across the Plasma Membrane Movement That Does Not Require Cellular Energy Process Definition Example Diffusion Solute travels across plasma membrane down its concentration gradient Movement of lipid-soluble materials across plasma membrane Facilitated diffusion Solute diffuses with help of a transporter Movement of glucose into cell Osmosis Solvent travels across plasma membrane down its concentration gradient Movement of water across plasma membrane Filtration Mechanical force pushes solute and solvent across plasma membrane Movement of solutes and water out of blood under force of blood pressure

Figure 3-6 Diffusion of a solid in a liquid.

Figure 3-7 Facilitated diffusion. Answer: 3-7 An increase in the number of transporters would increase the rate of facilitated diffusion. A decrease in the number of transporters would decrease the rate of facilitated diffusion. How would a change in the number of transporters affect a solute’s movement by facilitated diffusion?

Figure 3-8 A simple demonstration of osmosis. Answer: 3-8 If the solute could pass through the membrane in this system, the solute and solvent molecules would equalize on the two sides of the membrane, and the fluid level would be the same on both sides. What would happen in this system if the solute could pass through the membrane?

Figure 3-9 Osmotic pressure. Answer: 3-9 If the concentration of solute was increased on side B of this system, the osmotic pressure would increase. What would happen to osmotic pressure if the concentration of solute were increased on side B of this system?

Movement of Substances Across the Plasma Membrane How Osmosis Affects Cells Another way to think about osmosis is in terms of solute concentration. Water Follows the Salt Low Solute High Water High Solute Low Water Osmosis

Movement of Substances Across the Plasma Membrane Solutions and Their Effects on Cells Solution Description Examples Effect on Cells Isotonic Has same solute concentration as cell 0.9% salt; 5% glucose None Hypotonic Has lower solute concentration than cell <0.9% salt; <5% glucose Cell takes in water and may burst (lysis) Hypertonic Has higher solute concentration than cell >0.9% salt; >5% glucose Cell loses water and shrinks (crenation)

Figure 3-10 The effect of osmosis on cells. Answer: 3-10 If lost blood were replaced with pure water, red blood cells would swell because the blood would become hypotonic to the cells. What would happen to red blood cells in the body if blood lost through injury were replaced with pure water?

Figure 3-11 Filtration. Answer: Zooming in answer here

Movement of Substances Across the Plasma Membrane

Movement of Substances Across the Plasma Membrane Movement That Requires Cellular Energy Process Definition Example Active transport Solute moves through plasma membrane against its concentration gradient with help of transporters Ion movement in nervous system and muscular system Endocytosis Large amounts of solute and solvent are transported into cell using vesicles Phagocytosis of waste materials by white blood cells Exocytosis Large amounts of solute and solvent are transported out of the using vesicles Release of neurotransmitters from neurons

Figure 3-12 Phagocytosis. Answer: 3-12 A lysosome would likely help to destroy a particle taken in by phagocytosis. What organelle would likely help to destroy a particle taken in by phagocytosis?

Figure 3-13 Exocytosis. Answer: Zooming in answer here

✓ Movement of Substances Across the Plasma Membrane Checkpoints 3-8 What types of movement through the plasma membrane do not require cellular energy? 3-9 What term describes a fluid that is the same concentration as the intracellular fluid? What type of fluid is less concentrated? More concentrated? Answers: 3-8 Diffusion, facilitated diffusion, osmosis, and filtration do not require cellular energy; active transport and bulk transport require cellular energy. Bulk transport includes endocytosis (phagocytosis, pinocytosis, receptor-mediated endocytosis) and exocytosis. 3-9 An isotonic solution has the same concentration as the intracellular fluid; a hypotonic solution is less concentrated; a hypertonic solution is more concentrated.

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz 3.4 Which process uses transporters but not ATP? Active transport Endocytosis Facilitated diffusion Simple diffusion

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz Answer 3.4 Which process uses transporters but not ATP? Active transport Endocytosis Facilitated diffusion Simple diffusion

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz 3.5 Which method transports bulk amounts of material into the cell using vesicles? Active transport Endocytosis Exocytosis Osmosis

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz 3.5 Which method transports bulk amounts of material into the cell using vesicles? Active transport Endocytosis Exocytosis Osmosis

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz 3.6 Cells crenate when they are placed in solutions that are Catatonic Hypertonic Hypotonic Isotonic

Movement of Substances Across the Plasma Membrane ? Movement of Substances Across the Plasma Membrane Pop Quiz Answer 3.6 Cells crenate when they are placed in solutions that are Catatonic Hypertonic Hypotonic Isotonic

Protein Synthesis Learning Outcomes Describe the composition, location, and function of the DNA in the cell. Compare the function of three types of RNA in cells. Explain briefly how cells make proteins.

Protein Synthesis Overview Proteins give a cell its structure and function. DNA directs protein synthesis. Nucleotides make up DNA DNA organized into genes Genes organized into chromosomes RNA participates in protein synthesis but is not part of chromosomes.

Figure 3-14 Subdivisions of a chromosome. Answer: Zooming in answer here

Protein Synthesis Structure of DNA and RNA DNA RNA Location In nucleus In cytoplasm Nucleotides A, G, C, and T A, G, C, and U Structure Double-stranded helix A-T G-C Single stranded Function - Makes up chromosomes - Divided into genes - Carries nucleotide codes for protein synthesis Manufactures protein according to DNA code Three main types mRNA rRNA tRNA

Figure 3-15 Structure of DNA. Answer: 3-15 The nucleotides pair up so that there is one large nucleotide and one smaller nucleotide in each pair. Two of the DNA nucleotides (A and G) are larger in size than the other two (T and C). How do the nucleotides pair up with regard to size?

Protein Synthesis Role of RNA Types Function mRNA Is built on a strand of DNA in the nucleus and transcribes the nucleotide code Moves to cytoplasm and attaches to a ribosome rRNA With protein makes up the ribosomes, the sites of protein synthesis in the cytoplasm Involved in the process of translating the genetic message into a protein tRNA Works with mRNA and rRNA to translate the genetic code into protein Each molecule of tRNA carries an amino acid that can be used to build a protein at the ribosome.

Protein Synthesis Two-Step Process of Protein Synthesis Transcription First step; occurs in nucleus DNA code is transcribed into mRNA by nucleotide base pairing Translation Second step; occurs in cytoplasm mRNA leaves nucleus and travels to ribosomes Ribosomes and tRNA translate mRNA into protein’s amino acid sequence

Figure 3-16 Transcription. Answer: Zooming in answer here

Figure 3-17 Translation. Answer: Zooming in answer here

✓ Protein Synthesis Checkpoints 3-10 What are the building blocks of nucleic acids? 3-11 What category of compounds does DNA code for in the cell? 3-12 What three types of RNA are active in protein synthesis? Answers: 3-10 The building blocks of nucleic acids are nucleotides. 3-11 DNA codes for proteins in the cell. 3-12 The three types of RNA active in protein synthesis are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

? Protein Synthesis Pop Quiz 3.7 Which DNA nucleotide pairs with adenine? Cytosine Guanine Thymine Uracil

? Protein Synthesis Pop Quiz Answer 3.7 Which DNA nucleotide pairs with adenine? Cytosine Guanine Thymine Uracil

? Protein Synthesis Pop Quiz 3.8 Which RNA is transcribed from DNA? Amino acid Messenger RNA Ribosomal RNA Transfer RNA

? Protein Synthesis Pop Quiz Answer 3.8 Which RNA is transcribed from DNA? Amino acid Messenger RNA Ribosomal RNA Transfer RNA

? Protein Synthesis Pop Quiz 3.9 What is synthesized during translation? Amino acid Protein Starch Triglyceride

? Protein Synthesis Pop Quiz Answer 3.9 What is synthesized during translation? Amino acid Protein Starch Triglyceride

Cell Division Learning Outcomes Name and briefly describe the stages in mitosis.

Cell Division Types of Cell Division Meiosis Produces gametes (n) Cuts chromosome number in half to prepare for union of egg and sperm during fertilization Mitosis Produces somatic cells (2n) Parent stem cell gives rise to two identical daughter cells

Cell Division Preparation for Mitosis DNA replicates during interphase Identical strands held together at centromere until they separate during mitosis DNA replication during interphase Mitosis

Cell Division

Cell Division Stages of Mitosis Description Prophase DNA strands coil into chromosomes Nucleolus and nuclear membrane disappear Centrioles move to opposite poles and form spindle Metaphase Chromosomes line up across center of cell Chromosomes attach to spindle Anaphase Centromeres split Identical chromosomes move toward opposite centrioles Telophase Chromosomes continue to move toward centrioles Nuclear membrane forms around each group of chromosomes Plasma membrane pinches off in middle of cell to form two new identical daughter cells

Figure 3-18 The stages of mitosis. Answer: 3-18 If the original cell has 46 chromosomes, each daughter cell will have 46 chromosomes after mitosis. If the original cell shown has 46 chromosomes, how many chromosomes will each new daughter cell have?

✓ Cell Division Checkpoints 3-13 What must happen to the DNA in a cell before mitosis can occur? During what stage in the cell life cycle does this occur? 3-14 What are the four stages of mitosis? Answers: 3-13 Before mitosis can occur, the DNA must replicate (double). Replication occurs during interphase. 3-14 The four stages of mitosis are prophase, metaphase, anaphase, and telophase.

? Protein Synthesis Pop Quiz 3.10 During which phase of mitosis are chromosomes first visible? Anaphase Metaphase Prophase Telophase

? Protein Synthesis Pop Quiz Answer 3.10 During which phase of mitosis are chromosomes first visible? Anaphase Metaphase Prophase Telophase

Cell Division Answers: #-# Answer here #-# Organs working together combine to form systems.

Cell Aging As cells multiply, changes occur that may lead to their damage or death. Free radical injury Enzyme injury Gene mutation Slowing cell activity Apoptosis

Cells and Cancer Learning Outcomes Discuss the role of cell changes in cancer, and list several cancer risk factors.

Cells and Cancer Development of Cancer Genetic mutations may cause uncontrolled cell division. Cells may spread (metastasize), producing cancer. Cancer cells form tumors, crowding out normal cells.

Cells and Cancer Cancer Risk Factors Heredity Chemicals Radiation Physical irritation Diet Viruses

? Cells and Cancer Pop Quiz 3.11 Which of the following is a cancer risk factor? A diet rich in fruits and vegetables A family history of cancer Regular exercise Regular use of sunscreen

? Cells and Cancer Pop Quiz Answer 3.11 Which of the following is a cancer risk factor? A diet rich in fruits and vegetables A family history of cancer Regular exercise Regular use of sunscreen

Case Study Learning Outcomes Use the case study to discuss the importance of cells to the functioning of the body as a whole.

Case Study Jim’s lifestyle put him at risk of having a heart attack. Stress Overweight Sedentary High blood pressure During his heart attack, oxygen deficiency damaged Jim’s cardiac muscle cells, making them unable to contract, which caused Jim’s heart to stop beating.

Word Anatomy Learning Outcomes Show how word parts are used to build words related to cells and their functions.

Word Anatomy Word Part Meaning Example cyt/o cell Cytology is the study of cells. endo- in, within The endoplasmic reticulum within the cytoplasm. hypo- deficient, below, beneath A hypotonic solution’s concentration is lower than cytoplasm’s. hyper- above, over, excessive A hypertonic solution’s concentration is higher than cytoplasm’s. exo- outside, out of, away In exocytosis, the cell moves material out from vesicles. pro- before, in front Prophase is the first stage of mitosis. meta- change During metaphase chromosomes change position and line up across the equator. ana- upward, back, again During anaphase, chromosomes move to opposite sides of the cell. tel/o end Telophase is the last stage of mitosis.