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42 Cards in this Set
- Front
- Back
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Outline the cell theory
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• Cells are the building blocks of structure in living things
• Cells are the smallest unit of life • Cells are derived from other cells by division • Cells contain a blueprint for their growth, development and behavior • Cells are the site of all the chemical reactions of life (metabolism |
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State that unicellular organisms carry out all the functions of life
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Nutrition
Reproduction Growth Homeostasis Metabolism Sensitivity |
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Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit.
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• Appreciation of relative size is required such as molecules (1nm), thickness of membranes (10 nm), viruses (100nm), bacteria (1 um), organelles (up to 10 um) and most cells (up to 100 um). The three-dimensional nature/shape of cells should be emphasized.
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Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification
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• Magnification = Size of image / actual size of specimen
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Explain the importance of the surface area to volume ratio as a factor limiting cell size
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• If the ratio is too small then substances will not enter the cell as quickly as they are required and waste products will accumulate because they are produced more rapidly. Also in relations to heat production and loss. If the ratio is too small then cells may overheat because the metabolism produces heat faster than it is lost over the cell’s surface
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7 State that multicellular organisms show emergent properties
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• Emergent properties arise from the interaction of component parts; the whole is greater than the sum of its parts.
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Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others
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• Cell type using some of the genes in its nucleus, but not others when a gene is being used in a cell we say that the gene is being expressed. The development of cells in different ways to perform different functions is called differentiation.
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9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways
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• Stem cells are defined as cells that have the capacity to self-renew by cell division and to differentiate. However, all the cells produced will differentiate in the same way and so they are no longer stem cells.
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Outline one therapeutic use of stem cells.
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• Juvenile- onset diabetes can be treated by transplanting pancreas tissue from donors after their death, but the supply of this tissue is insufficient. A reliable method for stimulating embryonic stem cells to become insulin0secreting cells might allow more patients with diabetes to be treated
• Stem cells have been transplanted into injured spinal cords of experimental animals and there has been some recover of mobility. • Greatest success: involves the bone marrow transplants |
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2.2.4 State that prokaryotic cells divide by binary fission
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• Prokaryotic cells divide by binary fission. This is an asexual method of reproduction in which a cell divides into the same sized cell. The cells are genetically identical and form the basis of a reproductive clone.
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2.3.6 Outline two roles of extracellular components
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The contents of cells are contained within the plasma membrane. However, cells may secrete material outside the plamsa membrane; for example, plant cells have an external wall and many animal cells secrete glycoproteins.
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Explain the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.
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The phosphor lipid has a ‘head’ composed of a glycerol group to which is attached one ionized phosphate group. This latter part of the molecule has hydrophilic properties (water loving) the rest of the phospholipid consists of two long fatty acids which consists of hydrocarbon chains. These tails have hydrophobic properties (water hating) so phospholipid is unusual in being partly hydrophilic and partly hydrophobic.
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Diffusion:
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is the free passage of molecules (and atoms and ions) from a region of their high concentration to a region of low concentration
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osmosis
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is the passive movement of water molecules, across a partially permeable membrane, froma region of lower solute concentration to a region of higher solute concentration.
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Explain passive transport across membranes by simple diffusion and facilated diffusion
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Diffusion is the particles movement from a region of high concentration to low concentration. Facilitated diffusion is when certain particles are unable to enter the membrane they go through channel proteins which make it easier for the particles. Water and oxygen go through simple diffusion without any trouble but other particles need gates and openings in the membrane where they will fit to go from a high concentration to a low concentration.
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6 Explain the role of protein pumps and ATP in active transport across membranes
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Active transport is the movement of substances across membranes using energy from ATP. Active transport can move substances against a concentration gradient. Protein pumps in the membrane are used for active transport. Each pump only transports particular substances so cells can control what is absorbed and what is expelled.
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2.4.7 Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane
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Proteins are synthesized by ribosomes and then enter the rough endoplasmic reticulum. Vesicles bud off from the rER and carry the proteins to the Golgi apparatus. The Golgi apparatus modifies the proteins. Vesicles bud off from the Golgi apparatus and carry the modified proteins to the plasma membrane
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2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and re-from during endocytosis and exocytosis
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Endocytosis is where a vesicle which is formed by the in folding of the plasma membrane. Exocytosis is where a vesicle membrane fuses with the plasma membrane. The membranes are able to form and break without loss of the continuity of the plasma membranes.
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2.5.2 State the tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue.
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Cancer when the cell division cycle is regulated in a number of ways. Certain agents can damage these regulatory elements.
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2.5.5 Explain how mitosis produces two genetically identical nuclei
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• The process of cell division produces genetically identical daughter cells.
• Conservation of chromosome number. The chromosome number in each of the daughter cells is the same as that of the original cell • During the S-phase, each chromosome is copied exact. The two copies of each chromosome are held together by a protein structure called a centromere. • Therefore just prior to the phases of mitosis there is actually double the number of chromosomes present in a cell. • Each chromosome in this state is represented by a pair of sister chromatids. These give the now classic cross image of the DNA (see image below) |
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6 State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis
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• Growth: multicellular organisms increase their size through growth. This growth involves increasing the number of cells through mitosis. These cells will differentiate and specialise their function.
• Tissue Repair: As tissues are damaged they can recover through replacing damaged or dead cells. This is easily observed in a skin wound. More complex organ regeneration can occur in some species of amphibian. • Asexual Reproduction: This the production of offspring from a single parent using mitosis. The offspring are therefore genetically identical to each other and to their “parent”- in other words they are clones. Asexual reproduction is very common in nature, and in addition we humans have developed some new, artificial methods. |
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3.1.1 State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen.
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CHNOPS= Carbon (c) ; Hydrogen (H) ; Nitrogen (N) ; Oxygen (O) ; Phosphate (P) and Sulfate (S)
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2 State that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium.
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• Sulfur: important element in amino acids and proteins and in some vitamins.
• Calcium: found in bones/teeth • Iron: found in haemoglobin. Constituent of electron transport molecules • Phosphorus: synthesis of nucleotides; ATP • Sodium: involved with potassium in membrane function and nerve impulse transport. |
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Outline the thermal, cohesive and solvent properties of water.
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Thermal properties: Water has a large heat capacity. This means that large amounts of energy are needed to raise its temperature. This is useful for organisms that use water as a habitat.
Cohesive: it binds to itself, due to polarity of water molecule. The positive hydrogen side of the molecule binds with the negative oxygen side of another water molecule. This is known as a hydrogen bond. Makes it difficult for small objects to break through. Solvent: The polar nature of water molecules form shells around charged and polar molecules, preventing them from clumping together and therefore keeping in solution. Because such a broad range of materials dissolve in water, it is known as a universal solvent. |
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3.1.6 Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium.
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Water's high specific heat allows it to absorb large amounts of energy and act as an insulator for all living things. For example, our bodies use water for the sweat to lower body temperature. The sweat absorbs a large amount of heat, and then evaporates carrying that heat away from the body. The solvent properties of water allow many substances to be carried dissolved in water in the blood of animals and sap of plants.
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3.2.1 Distinguish between organic and inorganic compounds.
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Organic compounds are defined as compounds containing carbon that are found in living things.
Inorganic compounds: are defined as having no carbon chain but can be found as well in living organisms. |
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Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides, and polysaccharides; fatty acids, glycerol and glycerides; amino acids, dipeptides and polypeptides.
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• Monosaccharide ---> Condensation Reaction ---> Disaccharide (Condensation, loss of a single water molecule)
• Disaccharide ---> Hydrolysis ---> Monosaccharide (Hydrolysis gain of single water molecule) • Fatty Acids + Glycerol ---> Condensation Reaction ---> Fats • Amino Acid (carboxyl group) + Amino Acid(amino group) ---> Condensation Reaction ---> Dipeptide • Dipeptides + Amino Acids ---> Condensation Reaction ---> Polysaccharide |
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three examples for each of monosaccharide’s, disaccharides and polysaccharides.
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• Monosaccharide: glucose and fructose and galactose
• Disaccharides: are maltose and lactose and sucrose. • Polysaccharides: are starch and cellulose and glycogen. |
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8 State one function of glucose, lactose and glycogen in animals and of fructose, sucrose and cellulose in plants.
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Glucose: transported into cells in the blood plasma and used as a respiratory substrate for respiration
Lactose: produced in mammary glands and secreted into the milk Glycogen: storage carboyhydrate formed from glucose in the liver and other cells Fructose: produced in cellular respiration and used in the production of sucrose Sucrose: produced in green leaves from glucose and fructose. Cellulose: manufactured in cells and laid down externally in bundles of fibres as the main component of the cell wall |
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3.2.9 State three functions of lipids.
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• Energy storage: fat in humans and oil in plants
• Heat insulation: a layer of fat under the skin reduces heat loss • Buoyancy: lipids are less dense than water so helps animals to float |
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3.3.2 : State the name of the four bases in DNA:
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• Thymine
• Adenine • Guanine • Cytosine |
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3.3.4: Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.
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The DNA molecule consists of two polynucleotide strands, paried together and held by hydrogen bonds. The two strands known as a double helix. The paring of bases between adenine and thymine and between cytosine and guanine . This pairing known as complementary base pairing makes it possible for the DNA to replicate.
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3.4.1: Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase followed by formation fo the new complementary strands by DNA polymerase
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When replication takes place, the enzyme helicase first unwinds the double helix . Next the two DNA strands are split apart at hundreds, sometimes thousands, of points along the strand. Each splitting point is an area where replication is occuring, called a replication bubble. In each replication bubble, new DNA is made by attaching free nucleotides to the original strand (called the template) by base-pairing rules with the help of the enzyme DNA polymerase. The process results in two identical DNA strands produced from one.
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Explain the significance of complementary base paring in the conservation of the base sequence of DNA.
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Because the nitrogenous bases that compose DNA can only pair with complementary bases, any two linked strands of DNA are necessarily complementary to one another. The fact that only complementary base pairs can join together means that in replication the newly formed strands must be complementary to the old strands, thus conserving the same base sequence as previously existed.
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State that DNA replication is semi-conservative
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Since half the original molecule is kept the same this arrangement is known to be a semi-conservative replication.
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Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase
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Stage 1: protein synthesis occurs in the nucleus where a complimentary copy of the code is made by the building of a molecule of mRNA
Stage2: the DNA double helix unwinds and the hydrogen bonds are broken at the site of the gene being transcribed Stage3: one strand of DNA, the coding strand is used as the template for transcription by complementary base pairing Stage 4: once the mRNA strand is formed it leaves the nucleus through pores in the nuclear membrane and passes to ribosomes in the cytoplasm where it can be read and used in the synthesis of a protein. |
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3.5.3: Describe the genetic code in terms of codons composed of triplets of bases.
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The code is a triplet code, meaning that each sequence of three bases stands for one of the 20 amino acids and is called a codon. The genetic code has more codons than there are amino acids.
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3.5.4: Explain the process of translation leading to polypeptide formation
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A final stage, a protein chain is assembled. Moving along the mRNA the codons from the start codon. In the ribosome for each mRNA codon the complementary anticodon of the tRNA acid complex slots into place and is temporarily held in position by hydrogen bonds. While there, the amino acids of tRNA move back into the cytoplasm for re0-use.once this is done the ribosome moves on to the next mRNA. This process continues until a ribosome meets a stop codon.
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3.6.1: Define Enzyme and Active site
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Enzyme: are biological catalysts made of protein.
Active site: an active site is a region of an enzyme molecule where the substrate molecule binds. |
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3.6.2: Explain Enzyme – substrate specificity
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The active site for an enzyme is very specific in shape, with very precise chemical properties. Active sites match the shape of their substrates. Other molecules do not fit or do not have the same chemical properties. The enzyme is therefore substrate specific. This enzyme is a lock, and the substrate is the key which can open it.
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3.6.3: Explain the effects of temperature, pH and substrate concentration on enzyme activity
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Substrate concentration: At low s.c. the enzyme activity is proportional to the substrate concentration, because of random collision between substrate and enzyme. Thus the more substrate the higher the rate. However at a high substrate concentration, at some point all active sites are occupied so raising the substrate concentration has no effect.
Temperature: Enzyme activity increases as temperature increases, often doubling with each 10°C. This is because collision between substrate and active site happen more frequently at higher temperatures, due to fast molecular movement. However at high temperatures enzymes are denatured and stop working. This is because heat causes vibrations inside the enzyme, which break bonds needed to maintain the structure. pH: There is an optimum at which enzyme activity is fastest ( mostly pH 7), and as pH increases or decreases from its optimum, enzyme activity is reduced. (acids and alkali denature enzymes) |
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3.6.4: Define Denautration:
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Denaturation: A structural change in a protein that results in a loss of its biological properties. This can be caused by pH or by temperature.
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