3.1 Die Jeans ist cool

Maak 'n 10 vraag quiz oor die volgende: 1. **B.F. Skinner (Behaviorisme):** Skinner se operante kondisioneringsteorie beklemtoon die rol van versterking en straf in die vorming van gedrag. In die konteks van huistaalontwikkeling kan ouers positiewe versterking, soos lof en aanmoediging, gebruik om taalvaardighede te versterk. Byvoorbeeld, om 'n kind te prys vir die gebruik van nuwe woorde of die vorming van sinne kan bydra tot die versterking van taalverwerwing. 2. **Ivan Pavlov (Behaviorisme):** Pavlov se klassieke kondisioneringsteorie fokus op die verband tussen stimuli en reaksies. In die huislike omgewing kan konsekwente blootstelling aan taalryke stimuli, soos om boeke te lees of gesprekke te voer, help om positiewe assosiasies met taal te skep. Dit kan bydra tot die ontwikkeling van 'n kind se taalvaardighede deur herhaalde blootstelling aan linguistiese stimuli. 3. **Jean Piaget (Kognitivisme en Konstruktivisme):** Piaget se kognitiewe ontwikkelingsteorie beklemtoon stadiums van intellektuele groei by kinders. In die huis kan ouers Piaget se idees toepas deur ouderdomsgepaste aktiwiteite en taalervarings te verskaf wat ooreenstem met 'n kind se kognitiewe stadium. Daarbenewens dui Piaget se konstruktivistiese perspektief daarop dat kinders hul begrip van taal aktief opbou deur interaksie en verkenning binne hul huislike omgewing. 4. **Lev Vygotsky (Kognitivisme en Konstruktivisme):** Vygotsky se sosiokulturele teorie beklemtoon die sosiale aard van leer en die belangrikheid van sosiale interaksies. In 'n huislike omgewing kan ouers 'n deurslaggewende rol in taalontwikkeling speel deur aan gesprekke, storievertelling en ander taalryke interaksies deel te neem. Die sone van proksimale ontwikkeling (ZPD) konsep dui daarop dat taalleer die doeltreffendste is wanneer dit binne 'n kind se ontwikkelingsgebied plaasvind, met ondersteuning van meer kundige individue, soos ouers. 5. **Jerome Bruner (Kognitivisme en Konstruktivisme):** Bruner se konstruktivistiese teorie beklemtoon die rol van aktiewe leer en ontdekking. In die huis kan ouers taalontwikkeling fasiliteer deur 'n omgewing te skep wat verkenning, gesprek en praktiese ervarings aanmoedig. Bruner se spiraalkurrikulumkonsep stel ook voor dat taalonderwerpe oor tyd herbesoek en uitgebrei word, wat bydra tot 'n kind se dieper begrip en bemeestering van taalvaardighede. 6. **Abraham Maslow (Humanisme):** Maslow se hiërargie van behoeftes identifiseer die belangrikheid daarvan om basiese behoeftes te vervul voor hoërvlakbehoeftes, insluitend selfaktualisering. In die huis spreek die verskaffing van 'n ondersteunende en koesterende omgewing 'n kind se basiese emosionele behoeftes aan, wat 'n gevoel van veiligheid bevorder wat bevorderlik is vir taalontwikkeling. Maslow se beginsels beklemtoon die belangrikheid daarvan om 'n positiewe en emosioneel veilige huislike omgewing vir optimale taalonderrig te skep. 7. **Carl Rogers (Humanisme):** Rogers se persoongesentreerde benadering beklemtoon empatie, egtheid en onvoorwaardelike positiewe agting. In die huis kan die toepassing van hierdie beginsels op kommunikasie 'n veilige ruimte skep vir kinders om hulself uit te druk. Ouers wat 'n kliëntgesentreerde kommunikasiestyl aanneem, kan gesonde taalontwikkeling bevorder deur oop dialoog aan te moedig en 'n positiewe houding teenoor taaluitdrukking te bevorder. 8. **George Siemens (Konnektivisme):** Siemens se konnektivismeteorie fokus op die belangrikheid van netwerke en verbintenisse in leer. In 'n tuisomgewing kan die benutting van tegnologie en sosiale netwerke kinders blootstel aan uiteenlopende taalinsette en -ervarings. Konnektivisme moedig die verkenning van verskeie hulpbronne aan, insluitend aanlyn taalmateriaal en interaktiewe taalleerhulpmiddels, om 'n kind se taalvaardighede te verbeter. 9. **Albert Bandura (Sosiale Leer):** Bandura se sosiale leerteorie beklemtoon die rol van waarneming en nabootsing in leer. In die huis leer kinders taal deur hul ouers en versorgers waar te neem en na te boots. Die modellering van behoorlike taalgebruik, gesprekvoering en die skep van 'n taalryke atmosfeer tuis dra by tot die sosiale aanleer van taalvaardighede. 10. **Howard Gardner (Multiple Intelligences):** Gardner se teorie van veelvuldige intelligensies dui daarop dat individue verskillende maniere het om intelligensie te leer en uit te druk. In die huis kan die erkenning en koestering van verskeie taalintelligensies, soos verbale-linguistiese of interpersoonlike intelligensies, 'n kind se unieke taalontwikkeling ondersteun. Die verskaffing van uiteenlopende taalervarings, soos storievertelling, drama of musiek, kan voorsiening maak vir verskillende taalkundige sterkpunte.

CARBOHYDRATES Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen in a ratio of about one carbon atom to two hydrogen atoms to one oxygen atom. The number of carbon atoms in a carbohydrate varies. Some carbohydrates serve as a source of energy. Other carbohydrates are used as structural materials. Carbohydrates can exist as monosaccharides, disaccharides, or polysaccharides. Monosaccharides A monomer of a carbohydrate is called a monosaccharide (MAHN-oh-SAK-uh-RIED). A monosaccharide—or simple sugar— contains carbon, hydrogen, and oxygen in a ratio of 1:2:1. The gen- eral formula for a monosaccharide is written as (CH2O)n, where n is any whole number from 3 to 8. For example, a six-carbon mono- saccharide, (CH2O)6, would have the formula C6H12O6. The most common monosaccharides are glucose, fructose, and galactose, as shown in Figure 3-6. Glucose is a main source of energy for cells. Fructose is found in fruits and is the sweetest of the monosaccharides. Galactose is found in milk. Notice in Figure 3-6 that glucose, fructose, and galactose have the same molecular formula, C6H12O6, but differing structures. The different structures determine the slightly different properties of the three compounds. Compounds like these sugars, with a single chemical formula but different structural forms, are called isomers (IE-soh-muhrz). SECTION 2 OBJECTIVES ● Distinguish between monosaccharides, disaccharides, and polysaccharides. ● Explain the relationship between amino acids and protein structure. ● Describe the induced fit model of enzyme action. ● Compare the structure and function of each of the different types of lipids. ● Compare the nucleic acids DNA and RNA. VOCABULARY carbohydrate monosaccharide disaccharide polysaccharide protein amino acid peptide bond polypeptide enzyme substrate active site lipid fatty acid phospholipid wax steroid nucleic acid deoxyribonucleic acid (DNA) ribonucleic acid (RNA) nucleotide C HO H C H OH C OH H C CH2OH H C H OH O Glucose C OH C O H OH C OH H CH2OH C H CH2OH Fructose C H HO C OH H C OH H C CH2OH H C H OH O Galactose Glucose, fructose, and galactose have the same chemical formula, but their structural differences result in different properties among the three compounds. FIGURE 3-6 Copyright © by Holt, Rinehart and Winston. All rights reserved. 56 CHAPTER 3 Disaccharides and Polysaccharides In living things, two monosaccharides can combine in a condensa- tion reaction to form a double sugar, or disaccharide (die-SAK-e-RIED). For example in Figure 3-4, the monosaccharides fructose and glu- cose can combine to form the disaccharide sucrose. A polysaccharide is a complex molecule composed of three or more monosaccharides. Animals store glucose in the form of the polysaccharide glycogen. Glycogen consists of hundreds of glucose molecules strung together in a highly branched chain. Much of the glucose that comes from food is ultimately stored in your liver and muscles as glycogen and is ready to be used for quick energy. Plants store glucose molecules in the form of the polysaccha- ride starch. Starch molecules have two basic forms—highly branched chains that are similar to glycogen and long, coiled, unbranched chains. Plants also make a large polysaccharide called cellulose. Cellulose, which gives strength and rigidity to plant cells, makes up about 50 percent of wood. In a single cellu- lose molecule, thousands of glucose monomers are linked in long, straight chains. These chains tend to form hydrogen bonds with each other. The resulting structure is strong and can be broken down by hydrolysis only under certain conditions. PROTEINS Proteins are organic compounds composed mainly of carbon, hydrogen, oxygen, and nitrogen. Like most of the other biological macromolecules, proteins are formed from the linkage of monomers called amino acids. Hair and horns, as shown in Figure 3-7a, are made mostly of proteins, as are skin, muscles and many biological catalysts (enzymes). Amino Acids There are 20 different amino acids, and all share a basic structure. As Figure 3-7b shows, each amino acid contains a central carbon atom covalently bonded to four other atoms or functional groups. A single hydrogen atom, highlighted in blue in the illustration, bonds at one site. A carboxyl group, —COOH, highlighted in green, bonds at a second site. An amino group, —NH2, highlighted in yel- low, bonds at a third site. A side chain called the R group, high- lighted in red, bonds at the fourth site. The main difference among the different amino acids is in their R groups. The R group can be complex or it can be simple, such as the CH3 group shown in the amino acid alanine in Figure 3-7b. The differences among the amino acid R groups gives different proteins very different shapes. The different shapes allow pro- teins to carry out many different activities in living things. Amino acids are commonly shown in a simplified way such as balls, as shown in Figure 3-7c. (a) Many structures, such as hair and horns are made of proteins. (b) Proteins are made up of amino acids. Amino acids differ only in the type of R group (shown in red) they carry. Polar R groups can dissolve in water, but nonpolar R groups cannot. (c) Amino acids have complex structures, so, in this and other textbooks, they are often simplified into balls. FIGURE 3-7 (b) Alanine (an amino acid) (c) Simplified version of amino acid CH3 H N OH C C H O H (a) Copyright © by Holt, Rinehart and Winston. All rights reserved. BIOCHEMISTRY 57 H H N C C OH H O H CH3 H2O Glycine Alanine H N OH C C H O H H H N C C H O H CH3 N OH C C H O H (a) (b) (a) The peptide bond (shaded blue) that binds amino acids together to form a polypeptide results from a condensation reaction that produces water. (b) Poly- peptides are commonly shown as a string of balls in this textbook and elsewhere. Each ball represents an amino acid. FIGURE 3-8 Substrate Products Enzyme 1 2 3 In the induced fit model of enzyme action, the enzyme can attach only to a substrate (reactant) with a specific shape. The enzyme then changes and reduces the activation energy of the reaction so reactants can become products. The enzyme is unchanged and is available to be used again. 3 2 1 FIGURE 3-9 Dipeptides and Polypeptides Figure 3-8a shows how two amino acids bond to form a dipeptide (die-PEP-TIED). In this condensation reaction, the two amino acids form a covalent bond, called a peptide bond (shaded in blue in Figure 3-8a) and release a water molecule. Amino acids often form very long chains called polypeptides (PAHL-i-PEP-TIEDZ). Proteins are composed of one or more polypep- tides. Some proteins are very large molecules, containing hun- dreds of amino acids. Often, these long proteins are bent and folded upon themselves as a result of interactions—such as hydrogen bonding—between individual amino acids. Protein shape can also be influenced by conditions such as temperature and the type of solvent in which a protein is dissolved. For exam- ple, cooking an egg changes the shape of proteins in the egg white. The firm, opaque result is very different from the initial clear, runny material. Enzymes Enzymes—RNA or protein molecules that act as biological catalysts—are essential for the functioning of any cell. Many enzymes are proteins. Figure 3-9 shows an induced fit model of enzyme action. Enzyme reactions depend on a physical fit between the enzyme molecule and its specific substrate, the reactant being catalyzed. Notice that the enzyme has folds, or an active site, with a shape that allows the substrate to fit into the active site. An enzyme acts only on a specific substrate because only that substrate fits into its active site. The linkage of the enzyme and substrate causes a slight change in the enzyme’s shape. The change in the enzyme’s shape weakens some chemical bonds in the substrate, which is one way that enzymes reduce activation energy, the energy needed to start the reaction. After the reaction, the enzyme releases the products. Like any catalyst, the enzyme itself is unchanged, so it can be used many times. An enzyme may not work if its environment is changed. For example, change in temperature or pH can cause a change in the shape of the enzyme or the substrate. If such a change happens, the reaction that the enzyme would have catalyzed cannot occur.

CHARACTERISTICS OF LIFE The world is filled with familiar objects, such as tables, rocks, plants, pets, and automobiles. Which of these objects are living or were once living? What are the criteria for assigning something to the living world or the nonliving world? Biologists have established that living things share seven characteristics of life. These characteristics are organization and the presence of one or more cells, response to a stimulus (plural, stimuli), homeostasis, metabolism, growth and development, reproduction, and change through time. Organization and Cells Organization is the high degree of order within an organism’s internal and external parts and in its interactions with the living world. For example, compare an owl to a rock. The rock has a spe- cific shape, but that shape is usually irregular. Furthermore, differ- ent rocks, even rocks of the same type, are likely to have different shapes and sizes. In contrast, the owl is an amazingly organized individual, as shown in Figure 1-2. Owls of the same species have the same body parts arranged in nearly the same way and interact with the environment in the same way. Copyright © by Holt, Rinehart and Winston. All rights reserved. ORGANISM (Barn Owl) ORGAN (Owl’s Ear) TISSUE (Nervous Tissue Within the Ear) CELL (Nerve Cell) Every living organism has a level of organization. The different levels of organization for a complex multicellular organism, such as an owl, are shown in the figure below. FIGURE 1-2 THE SCIENCE OF LIFE 7 All living organisms, whether made up of one cell or many cells, have some degree of organization. A cell is the smallest unit that can perform all life’s processes. Some organisms, such as bacteria, are made up of one cell and are called unicellular (YOON-uh-SEL-yoo-luhr) organisms. Other organisms, such as humans or trees, are made up of multiple cells and are called multicellular (MUHL-ti-SEL-yoo-luhr) organisms. Complex multicellular organisms have the level of orga- nization shown in Figure 1-2. In the highest level, the organism is made up of organ systems, or groups of specialized parts that carry out a certain function in the organism. For example, an owl’s ner- vous system is made up of a brain, sense organs, nerve cells, and other parts that sense and respond to the owl’s surroundings. Organ systems are made up of organs. Organs are structures that carry out specialized jobs within an organ system. An owl’s ear is an organ that allows the owl to hear. All organs are made up of tissues. Tissues are groups of cells that have similar abilities and that allow the organ to function. For example, nervous tissue in the ear allows the ear to detect sound. Tissues are made up of cells. A cell must be covered by a membrane, contain all genetic information necessary for replication, and be able to carry out all cell functions. Within each cell are organelles. Organelles are tiny structures that carry out functions necessary for the cell to stay alive. Organelles contain biological molecules, the chemical compounds that provide physical structure and that bring about movement, energy use, and other cellular functions. All biological molecules are made up of atoms. Atoms are the simplest particle of an ele- ment that retains all the properties of a certain element. Response to Stimuli Another characteristic of life is that an organism can respond to a stimulus—a physical or chemical change in the internal or external environment. For example, an owl dilates its pupils to keep the level of light entering the eye constant. Organisms must be able to respond and react to changes in their environment to stay alive. ORGANELLE (Mitochondrion) BIOLOGICAL MOLECULE (Phospholipid) ATOM (Oxygen) cell from the Latin, cella meaning “small room,” or “hut” Word Roots and Origins www.scilinks.org Topic: Characteristics of Life Keyword: HM60257 mb06se_bios01.qxd 5/18/07 10:37 AM Page 7 8 CHAPTER 1 Homeostasis All living things, from single cells to entire organisms, have mecha- nisms that allow them to maintain stable internal conditions. Without these mechanisms, organisms can die. For example, a cell’s water content is closely controlled by the taking in or releas- ing of water. A cell that takes in too much water will rupture and die. A cell that doesn’t get enough water will also shrivel and die. Homeostasis (HOH-mee-OH-STAY-sis) is the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. Organisms have regulatory systems that maintain internal conditions, such as temperature, water content, and uptake of nutrients by the cell. In fact, multi- cellular organisms usually have more than one way of maintain- ing important aspects of their internal environment. For example, an owl’s temperature is maintained at about 40°C (104°F). To keep a constant temperature, an owl’s cells burn fuel to produce body heat. In addition, an owl’s feathers can fluff up in cold weather. In this way, they trap an insulating layer of air next to the bird’s body to maintain its body temperature. Metabolism Living organisms use energy to power all the life processes, such as repair, movement, and growth. This energy use depends on metabolism (muh-TAB-uh-LIZ-uhm). Metabolism is the sum of all the chemical reactions that take in and transform energy and materials from the environment. For example, plants, algae, and some bacteria use the sun’s energy to generate sugar molecules during a process called photosynthesis. Some organisms depend on obtaining food energy from other organisms. For instance, an owl’s metabolism allows the owl to extract and modify the chemi- cals trapped in its nightly prey and use them as energy to fuel activities and growth. Growth and Development All living things grow and increase in size. Some nonliving things, such as crystals or icicles, grow by accumulating more of the same material of which they are made. In contrast, the growth of living things results from the division and enlargement of cells. Cell division is the formation of two new cells from an existing cell, as shown in Figure 1-3. In unicellular organisms, the primary change that occurs following cell division is cell enlargement. In multi- cellular life, however, organisms mature through cell division, cell enlargement, and development. Development is the process by which an organism becomes a mature adult. Development involves cell division and cell differen- tiation, or specialization. As a result of development, an adult organism is composed of many cells specialized for different func- tions, such as carrying oxygen in the blood or hearing. In fact, the human body is composed of trillions of specialized cells, all of which originated from a single cell, the fertilized egg. This unicellular organism, Escherichia coli, inhabits the human intestines. E. coli reproduces by means of cell division, during which the original cell splits into two identical offspring cells. FIGURE 1-3 Observing Homeostasis Materials 500 mL beakers (3), wax pen, tap water, thermometer, ice, hot water, goldfish, small dip net, watch or clock with a second hand Procedure 1. Use a wax pen to label three 500 mL beakers as follows: 27°C (80°F), 20°C (68°F), 10°C (50°F). Put 250 mL of tap water in each beaker. Use hot water or ice to adjust the tem- perature of the water in each beaker to match the temperature on the label. 2. Put the goldfish in the beaker of 27°C water. Record the number of times the gills move in 1 minute. 3. Move the goldfish to the beaker of 20°C water. Repeat observations. Move the goldfish to the beaker of 10°C. Repeat observations. Analysis What happens to the rate at which gills move when the temp- erature changes? Why? How do gills help fish maintain homeostasis? Quick Lab mb06se_bios01.qxd 5/18/07 10:37 AM Page 8 THE SCIENCE OF LIFE 9 Reproduction All organisms produce new organisms like themselves in a process called reproduction. Reproduction, unlike other characteristics, is not essential to the survival of an individual organism. However, because no organism lives forever, reproduction is essential for the continuation of a species. Glass frogs, as shown in Figure 1-4, lay many eggs in their lifetime. However, only a few of the frogs’ off- spring reach adulthood and successfully reproduce. During reproduction, organisms transmit hereditary informa- tion to their offspring. Hereditary information is encoded in a large molecule called deoxyribonucleic acid, or DNA. A short segment of DNA that contains the instructions for a single trait of an organism is called a gene. DNA is like a large library. It contains all the books—genes—that the cell will ever need for making all the struc- tures and chemicals necessary for life. Hereditary information is transferred to offspring during two kinds of reproduction. In sexual reproduction, hereditary information recombines from two organisms of the same species. The resulting offspring are similar but not identical to their parents. For example, a male frog’s sperm can fertilize a female’s egg and form a single fer- tilized egg cell. The fertilized egg then develops into a new frog. In asexual reproduction, hereditary information from different organisms is not combined; thus the original organism and the new organism are genetically the same. A bacterium, for example, reproduces asexually when it splits into two identical cells. Change Through Time Although individual organisms experience many changes during their lifetime, their basic genetic characteristics do not change. However, populations of living organisms evolve or change through time. The ability of populations of organisms to change over time is important for survival in a changing world. This factor is also impor- tant in explaining the diversity of life-forms we see on Earth today.

The endoplasmic reticulum (EN-doh-PLAZ-mik ri-TIK-yuh-luhm), abbre- viated ER, is a system of membranous tubes and sacs, called cisternae (sis-TUHR-nee). The ER functions primarily as an intracellu- lar highway, a path along which molecules move from one part of the cell to another. The amount of ER inside a cell fluctuates, depending on the cell’s activity. There are two types of ER: rough and smooth. The two types of ER are thought to be continuous. Rough Endoplasmic Reticulum The rough endoplasmic reticulum is a system of interconnected, flattened sacs covered with ribosomes, as shown in Figure 4-15. The rough ER produces phospholipids and proteins. Certain types of proteins are made on the rough ER’s ribosomes. These proteins are later exported from the cell or inserted into one of the cell’s own membranes. For example, ribosomes on the rough ER make digestive enzymes, which accumulate inside the endoplasmic retic- ulum. Little sacs or vesicles then pinch off from the ends of the rough ER and store the digestive enzymes until they are released from the cell. Rough ER is most abundant in cells that produce large amounts of protein for export, such as cells in digestive glands and antibody-producing cells. Smooth Endoplasmic Reticulum The smooth ER lacks ribosomes and thus has a smooth appear- ance. Most cells contain very little smooth ER. Smooth ER builds lipids such as cholesterol. In the ovaries and testes, smooth ER produces the steroid hormones estrogen and testosterone. In skeletal and heart muscle cells, smooth ER releases calcium, which stimulates contraction. Smooth ER is also abundant in liver and kidney cells, where it helps detoxify drugs and poisons. Long-term abuse of alcohol and other drugs causes these cells to produce more smooth ER. Increased amounts of smooth ER in liver cells is one of the factors that can lead to drug tolerance. As Figure 4-15 shows, rough ER and smooth ER form an interconnected network. Copyright © by Holt, Rinehart and Winston. All rights reserved. reticulum from the Latin rete, meaning “net”; reticulum means “little net” Word Roots and Origins The endoplasmic reticulum (ER) serves as a site of synthesis for proteins, lipids, and other materials. The dark lines in the photo represent the membranes of the ER, and the narrow lighter areas between the dark lines show the channels and spaces (cisternae) inside the ER. FIGURE 4-15 Smooth ER Ribosomes Rough ER Cisternae 82 CHAPTER 4 GOLGI APPARATUS The Golgi apparatus, shown in Figure 4-16, is another system of flattened, membranous sacs. The sacs nearest the nucleus receive vesicles from the ER containing newly made proteins or lipids. Vesicles travel from one part of the Golgi apparatus to the next and transport substances as they go. The stacked membranes modify the vesicle contents as they move along. The proteins get “address labels” that direct them to various other parts of the cell. During this modification, the Golgi apparatus can add carbohydrate labels to proteins or alter new lipids in various ways. VESICLES Cells contain several types of vesicles, which perform various roles. Vesicles are small, spherically shaped sacs that are surrounded by a single membrane and that are classified by their contents. Vesicles often migrate to and merge with the plasma membrane. As they do, they release their contents to the outside of the cell. Lysosomes Lysosomes (LIE-suh-SOHMZ) are vesicles that bud from the Golgi appa- ratus and that contain digestive enzymes. These enzymes can break down large molecules, such as proteins, nucleic acids, car- bohydrates, and phospholipids. In the liver, lysosomes break down glycogen in order to release glucose into the bloodstream. Certain white blood cells use lysosomes to break down bacteria. Within a cell, lysosomes digest worn-out organelles in a process called autophagy (aw-TAHF-uh-jee). Lysosomes are also responsible for breaking down cells when it is time for the cells to die. The digestion of damaged or extra cells by the enzymes of their own lysosomes is called autolysis (aw-TAHL-uh-sis). Lysosomes play a very important role in maintaining an organism’s health by destroying cells that are no longer functioning properly. Copyright © by Holt, Rinehart and Winston. All rights reserved. The Golgi apparatus modifies many cellular products and prepares them for export. FIGURE 4-16 CELL STRUCTURE AND FUNCTION 83 Peroxisomes Peroxisomes are similar to lysosomes but contain different enzymes and are not produced by the Golgi apparatus. Peroxisomes are abundant in liver and kidney cells, where they neutralize free radicals (oxygen ions that can damage cells) and detoxify alcohol and other drugs. Peroxisomes are named for the hydrogen peroxide, H2O2, they produce when breaking down alco- hol and killing bacteria. Peroxisomes also break down fatty acids, which the mitochondria can then use as an energy source. Other Vesicles Specialized peroxisomes, called glyoxysomes, can be found in the seeds of some plants. They break down stored fats to provide energy for the developing plant embryo. Some cells engulf material by surrounding it with plasma membrane. The resulting pocket buds off to become a vesicle inside the cell. This vesicle is called an endosome. Lysosomes fuse with endosomes and digest the engulfed material. Food vacuoles are vesicles that store nutrients for a cell. Contractile vacuoles are vesicles that can contract and dispose of excess water inside a cell. Protein Synthesis One of the major functions of a cell is the production of protein. The path some proteins take from synthesis to export can be seen in Figure 4-17. In step , proteins are assembled by ribosomes on the rough ER. Then, in step , vesicles transport proteins to the Golgi apparatus. In step , the Golgi modifies proteins and pack- ages them in new vesicles. In step , vesicles release proteins that have destinations outside the cell. In step , vesicles containing enzymes remain inside the cell as lysosomes, peroxisomes, endo- somes, or other types of vesicles. 5 4 3 2 1 Copyright © by Holt, Rinehart and Winston. All rights reserved. Proteins are assembled by ribosomes on the rough ER. Vesicles carry proteins from the rough ER to the Golgi apparatus. Proteins are modified in the Golgi apparatus and enter new vesicles. Some vesicles release their proteins outside the cell. Other vesicles remain in the cell and become lysosomes and other vesicles. Nucleus

Maak 'n 10 vraag toets oor die volgende:1. **Kognitiewe Ontwikkelingsteorie:** - Kinders ontwikkel hul taalvermoë deur kognitiewe prosesse. - In die grondslagfase moet onderrig aangepas wees aan die kognitiewe ontwikkeling van die kind. - Stimuleer kreatiewe denke en vermoëns deur interaktiewe en sinnige taalaktiwiteite. 2. **Sosiale Interaksie-teorie (Vygotsky):** - Leer vind plaas binne 'n sosiale konteks. - Onderwysers moet sorg vir taalryke omgewings waar leerders met mekaar kan interageer. - Fokus op groepsaktiwiteite en samehang tussen leerders om kommunikasie te bevorder. 3. **Taalontwikkelingsmodelle (Piaget):** - Kinders gaan deur spesifieke fases van taalontwikkeling. - Rig onderrig op die unieke ontwikkelingsvlakke van kinders in die grondslagfase. - Pas aktiwiteite aan om te pas by die konkrete denkvermoëns van jong kinders. 4. **Kognitiewe Neuro-wetenskaplike Benadering:** - Verstaan die neurologiese aspekte van taalverwerwing. - Integreer sieninge van kognitiewe neuro-wetenskap in onderrigmetodes. - Bevorder taalontwikkeling deur stimulering van die relevante breingebiede. 5. **Generatiewe Taalteorie (Chomsky):** - Fokus op die aanleer van taalstrukture en grammatika. - Integreer geleenthede vir kinders om taalstrukture te eksperimenteer en toe te pas. - Moedig kreatiewe taalgebruik aan terwyl die basiese taalstrukture aangeleer word. 6. **Kontekstuele Leerteorie:** - Leer moet plaasvind in 'n konteks wat betekenisvol is vir die leerders. - In die grondslagfase moet onderrig aktiewe betrokkenheid en praktykgebaseerde leer insluit. - Skep geleenthede vir taalgebruik in alledaagse situasies. 7. **Kommunikatiewe Taalonderrig (Krashen):** - Leerders verwerf taal deur eksponering aan kommunikatiewe situasies. - Skep 'n omgewing waar kommunikasie en interaksie in Afrikaans aangemoedig word. - Fokus op funksionele taalgebruik en praktiese kommunikasie.

Groups of plants according to life cycle 1.Annual plants: •These are plants that live for one year or one season. •They grow, flower and produce seed and die in one season or year. •Maize and sorghum are examples of annual plants. 2. Biennial plants: •These are plants which require two seasons to complete their life cycle. •The produce flowers in the first year and mature in the second year. •Examples of biennial plants are carrots, cassava 3. Perennial plants: •These are plants that live for more than two years. •Once they have started producing fruit they will continue producing fruits every year. •Most fruit trees are perennials. •Some grass are plants are also perennials for example sugar cane.

Für das Behalten des Notensystems - Das Notensystem in Schulen abzuschaffen ist eine radikale Idee, die jedoch einige schwerwiegende Probleme mit sich bringen könnte. Hier sind sieben Argumente, die dagegen sprechen: 1. **Objektive Bewertung:** Noten bieten eine objektive Möglichkeit, den Fortschritt der Schüler zu bewerten. Sie basieren auf messbaren Leistungen und ermöglichen einen Vergleich zwischen verschiedenen Schülern. 2. **Motivation zur Leistung:** Noten dienen als Anreiz für Schülerinnen und Schüler, sich anzustrengen und gute Leistungen zu erbringen. Ohne sie könnte die Motivation zum Lernen abnehmen, da der Anreiz für herausragende Leistungen fehlen würde. 3. **Transparenz für Schüler, Eltern und Arbeitgeber:** Noten bieten eine klare Rückmeldung über den Leistungsstand der Schüler. Sie sind eine wichtige Referenz für Eltern, Schüler und zukünftige Arbeitgeber bei der Bewertung der Leistungsfähigkeit. 4. **Vorbereitung auf die Realität:** In der Arbeitswelt werden Leistungen oft anhand von Bewertungen gemessen. Das Notensystem bereitet Schülerinnen und Schüler auf diese Realität vor und lehrt sie, mit Druck und Wettbewerb umzugehen. 5. **Effiziente Beurteilung:** Noten ermöglichen eine effiziente Beurteilung der Leistungen von Schülern. Sie erleichtern Lehrern die Bewertung einer großen Anzahl von Schülern und ermöglichen einen strukturierten Unterricht. 6. **Erfassung unterschiedlicher Fähigkeiten:** Noten berücksichtigen verschiedene Aspekte der Leistung, einschließlich Wissen, Verständnis, Anwendung und Analyse. Sie bieten somit eine umfassende Bewertung der Fähigkeiten eines Schülers. 7. **Bewährtes System:** Das Notensystem ist seit langem ein etabliertes Bewertungsinstrument in Schulen und hat sich als effektiv erwiesen. Es gibt keinen überzeugenden Grund, ein bewährtes System aufzugeben, das den Anforderungen der Bildungswelt gerecht wird. Insgesamt bietet das Notensystem in Schulen eine effektive Möglichkeit, den Fortschritt und die Leistung der Schüler zu bewerten und sie auf die Anforderungen der Realität vorzubereiten. Seine Abschaffung könnte zu erheblichen Problemen führen und wäre daher nicht ratsam.

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