SNS - Biology Flashcards

Question

Communities

Answer 1

An assembly of different species, eg different types of coral, fish, arthropods etc in a coral reef

Answer 2

A group of orgainisms from the same species that lives in the same niche. Highly dynamic and can fluctuate dramatically in number

Answer 3

the study of population dynamics

Answer 4

The limit to the number of individuals of a species. Based on the concept that a niche has a finite amount of resources to support a population

Answer 5

Those that have few offspring and invest heavily in parental care

Answer 6

Those that have a large number of offspring and provide little parental investment

Answer 7

Extreme example of genetic drift. Whereby a small number of individuals branch off from the main population and colonise a new habitat. When a population becomes reproductively isolated, the 'colonising group' becomes the 'founder' of a new species

Answer 8

Arises from the geographical separation of population preventing gene flow and resulting in natural selection operating differently on the two populations

Answer 9

Occurs when a small part of a larger population branches off in the absence of geographical barriers

Answer 10

Whena new species originates within a larger population, usually resulting from a genetic mutation. Occurs frequently in plants with chromosome doubling

Answer 11

Mutations can by chance, rapidly change the genetic composition of a small population

Answer 12

A hypothetical model that examines circumstances that cause evolution. If random sexual selection is the only factor affecting allele frequencies, no evolution would occur - a situation known as the Hardy-Weinberg equilibrium. If, however, there are mutations or unequal reproductive successes among individuals within a population, allele frequencies will not match those for the Hardy-Weinberg equilibrium and evolution will occur

Answer 13

CHanges in the allele frequency within a population

Answer 14

p^2 + 2pq + q^2 = 1 Where p = the frequency of the dominant allele, and q = is the frequency of the recessive allele in a given population

Answer 15

Or convergent evolution. Independent evolution of similar structures in species which do not have similar lineages

Answer 16

Or divergent evolution. Gives rise to similar structures in species from a common ancestral lineage

Answer 17

The study of the groupings of organisms. An ancestor and all of its descendents are grouped into a clade

Answer 18

Length of branches in a phylogram indicate the number of genetic changes that have occured since a common evolutionary ancestor. Therefore give infomation on evolution. Cladograms give information on groupings of organisms

Answer 19

Tends to select for characteristics of an organism which make it better suited to its environment

Answer 20

The process by which the genetic makeup of populations change over time

Answer 21

Determined by the ability to produce viable offspring

Answer 22

A change over time in the genetic makeup of a population that increases its fitness

Answer 23

The two DNA strands are antiparallel: one 5' to 3' and the other 3' to 5'. During replication bases are added to the 3' end of the template, making the overall direction fo replication 5' to 3'

Answer 24

Because strands are antiparallel and only one portion of the DNA is unwound at a time, only one strand - the leading stand- will alllow for the 5' to 3' directional addition

Answer 25

Small fragment of DNA transcribed from the lagging strand in the 5' to 3' direction and joined together

Answer 26

Process by which the portion of DNA encoding a specific protein is base paired with RNA nucleotides creating a complementary strand of RNA called mRNA

Answer 27

Strand of DNA that permits the mRNA strand to grow in a 5' to 3' direction

Answer 28

Strand of DNA that isn't used as a template

Answer 29

Base pair inverted form of the original DNA sense strand containing U in place of T

Answer 30

1. DNA helicase unwinds the two DNA strands 2. Single stranded binding protein helps stabilise the unwound DNA strands 3. A small piece of RNA acts as a primer, which is necessary to begin replication process. Only one primer is necessary for replication of the leading strand while multiple primers are needed for replication of the lagging strand 4. DNA polymerase III adds nucleotides to the 3' end of the primer following the base pairing of nucleotides. Also corrects base pairing errors 5. DNA polymerase replaces the RNA primer with DNA nucleotides 6. DNA ligase joins the Okazaki fragments of the lagging strand as well as the DNA replacing the RNA primer in the leading strand 7. Following replication, each new helix is composed of one parent strand and one newly replicated strand

Answer 31

1. Initiation 2. Elongation 3. Termination

Answer 32

Begins when the promoter protein binds to the DNA at the starting point of transcription, unwinding the DNA

Answer 33

Occurs when RNA polymerase adds RNA nucleotides, again following the base pairing rule

Answer 34

Different in prokaryotes and eukaryotes In eukaryotes a specific sequence of nucleotides indicates the end of transcription is near. RNA polymerase continues to add 50-250 base pairs before cutting the mRNA free. The mRNA then receives a cap of modifies guanine and a tial of 50-250 adenine nucleotides. Exons, the coding portions, are spliced tgether while the non-coding introns are excised

Answer 35

The newly-transcribed mRNA then receives a cap of modifies guanine and a tial of 50-250 adenine nucleotides. Exons, the coding portions, are spliced together while the non-coding introns are excised. The modified mRNA exits the nucleus and enters the cytoplasm where it will be translated into a protein

Answer 36

The bases on a strand of mRNA code for different amino acids which assemble to form proteins during the process of translation. Different codons - combinations of three base pairs - correspond to each of the 20 amino acids. tRNA is responsible for decoding the message and adding the appropriate amino acids. Ends when a tRNA reaces a stop codon on the mRNA such as UGA which doesn't code for an amino acid

Answer 37

tRNA is responsible for decoding the message and adding the appropriate amino acids. Each has an anticodon sequence that is complementry to the mRNA. The other end has a specific amino acid attached to it

Answer 38

Moves along the mRNA strand. Responsible for holding the tRNA in place while the peptide bond between amino acid is taking place. Have three distinct regions: E site, P site and A site. Proteins that are bound for extracellular release, such as neurotransmitters are translated on ribosomes in the rough ER. Proteins destined to stay within the cell are translated in free ribosomes

Answer 39

exit site for the tRNA that has just finished adding its amino acid

Answer 40

For the tRNA that is actively creating a peptide bond int eh growing polypeptide chain

Answer 41

For tRNA that is bringing the amino acid to be added after that occupying the P site

Answer 42

Composeed of one molecule of the sugar deoxyribose, one phosphate group and one of four nitrogenous bases: adenine, cytosine, guanine or thymine

Answer 43

Double helix witha sugar-phosphate backbone and rings of paired nucleotide bases. Two hydrogen bonds link A and T while three join G and C

Answer 44

Can be single or double stranded. Different to DNA in its composition in that the sugar ribose replaces deoxyribose and the nitrogenous base Uracil replaced thymine

Answer 45

During metaphase I of meiosis when chromosomes line up at the metaphase plate, there is no force that governs maternal chromosomes to orient themselves towards one pole and paternal chromosomes towards the other. For each homolougous pair, there is a 50% chance that the maternal chromosome will situate itself at a particular pole. Chromosome1 has no effect on the positioning of chromosome 7 - they are independent. Without considering crossing-over, the number of combinations of a daughter cell formed by meiosis of a parent cell with two homologous pairs of chromosomes is four

Answer 46

Means genes for two given traits are linked on the same chromosome and will not follow Mendalian laws for independent assortment. Genes that are close together on the same chromosome are more likely to be inherited together. Genes that are farther apart are more likely to be separated by crossing=over and exchange

Answer 47

The rate at which two genes become unlinked. By establishing this, it is possible to create genetic maps which show the locations of the various alleles on the chromosome

Answer 48

Located on sex chromosomes. The X chromosome is much larger than the Y and carries these genes. As females have two X chromosomes, the dominant sex-linked allele is expressed and the recessive is not. In males any allele on the one X chromosome is expressed

Answer 49

A woman can be heterozygous for a recessive sex-linked disease and act as a carrier. She is not affected but there i a 50% probability that her sons will suffer from the disease. The male X chromosome is passed onlyto female offspring. Therefore an affected male can pass the condition to female but not male offspring. If a daughter is homozygous for the recessive allele she will suffer from the condition. If she is heterozygous, she will act as a carrier

Answer 50

Depict the pattern of inheritance of a particular trait in a family and gives information on gene transfer. Females are represented as circles and males as squares. Solid coloured shapes indicate that an individial has the trait/disease tracked.A dot or partially shaded shape indicates that an individual is a carrier

Answer 51

Many unicellular and some multicellular organisms reproduce via asexual reproduction. The process results in offspring that are genetically identical to the parent. There are three types: 1. Binary fission 2. Budding 3. Fragmentation

Answer 52

Occurs in some single-celled organisms such as bacteria and amoeba. Genetic material within the parent cell is replicated while the cell elongates After the DNA is duplicated, the cell dives in half producing two identical daughter cells.The process is similar to mitosis but the latter involves nuclear disintegration and guidance of chromosomes by microtubules

Answer 53

Yeast cells. Small bud cells are pinched off of from the parent by cell division

Answer 54

eg earthworms and plantsWhereby an organism may become fragmented into multiple pieces. Some or all of these fragments may grow into complete adults

Answer 55

1. Mutations 2. Transformation 3. Transduction 4. Conjugation

Answer 56

Naked DNA from the environment is taken up by the prokaryotic cell and incorporated into its chromosome

Answer 57

Bacteriophages (viruses that infect bacteria) carry pieces of DNA from one bacteria to another

Answer 58

Involves direct one-way transfer of genetic material from one organism to another. The donor extends a sex pilus to the recipient. A cytoplasmic bridge then forms between the two cells. A single strand of DNA from the donor's bacterial chromosome or plasmid is transfered to the recipient. The bridge then breaks and the transferred DNA is taken up by the recipient's bacterial chromosome or plasmid

Answer 59

Combines genetic material from two different sources to create offspring. Specialised germ cells undergo meiotic division and come together to form new individuals with new genetic combinations. Unlike mitosis which produces diploid cells (2N), meosis produces haploid gamete cells (1N). Even greater genetic diversity can be generated as genes are exchanged between chromosomes during crossing over during prophase I or meosis

Answer 60

Have two sets of chromosomes, one from each parent

Answer 61

Have half the chromosome number. Referred to as haploid

Answer 62

The full complement of genetic material includes 22 chrmosome pairs called autosomes which don't differ between the sexes and an additional pair of sex chromosomes. Total of 23 pairs

Answer 63

For example coat colour in rabbits - multiple alleles with varying degrees of dominance determine the resulting coat colour

Answer 64

Traits determined by the additive effect of two or more genes

Answer 65

Affect more than one phenotypic characteristic

Answer 66

Situation in which one allele doesn't completely block the expression of another and alleles blend to form the phenotype. eg petal colour in snapdragons. If red (RR) and white (rr) floering plants are produced, the offspring will have pink flowers (Rr)

Answer 67

Where a heterozygous phenotype expresses both alleles equally. For example, blood types - determined by the alleles IA, IB and i corresponding to different types of antigens in the blood. An individual who is homozygous for IA or IB has an A or B phenotype. An individual who is heterozygous for IA and IB has an AB phenotype

Answer 68

Alternative forms of a single gene. For any inherited trait, an individual possesses an allele from each parent

Answer 69

States that during meiosis, the two alleles from each parent segregate from each other resulting in gametes that each carry one allele for each trait

Answer 70

States that if the two alleles for a trait are different one allele will be dominant (fully expressed in the individual) and the other will be recessive (will not show itself)

Answer 71

The genetic makeup of an organism

Answer 72

Actual physical characteristics of an organism

Answer 73

1, BB x bb 2. Bb x bb 3. Bb x Bb

Answer 74

A 9:3:3:1 ratio is characterisic of crosses between individuals that are either homozygous recessive or homozygous dominant for two different independently assorting traits

Answer 75

After eight weeks of growth, an embryo is known as a fetus

Answer 76

1. In the first few weeks, the placenta and unbilical cord form and become the specialised circulatory system between mother and fetus. This system provides nourushment via oxygenated blood in the unmbilical vein and removes metabolic waste via the umbilical arteries

Answer 77

Develops from two embryonic sacs - the yolk sac ( the site of early blood vessel development) and the allantois (an outpocketing of the gut that contains many blood vessels)

Answer 78

Formed when part of the chorion fuses to the uterine walls. In addition to supplying nutrients and removing waste, prevents toxins and drugs from entering the fetus and functions as an exocrine gland, producing the essential hormones of pregnancy: oestorgen, progesterone and hCG

Answer 79

A membrane that surrounds the amnion

Answer 80

The strong sac that houses the fetus and contains amniotic fluid

Answer 81

exit site for the tRNA that has just finished adding its amino acid

Answer 82

For the tRNA that is actively creating a peptide bond int eh growing polypeptide chain

Answer 83

For tRNA that is bringing the amino acid to be added after that occupying the P site

Answer 84

Composeed of one molecule of the sugar deoxyribose, one phosphate group and one of four nitrogenous bases: adenine, cytosine, guanine or thymine

Answer 85

Double helix witha sugar-phosphate backbone and rings of paired nucleotide bases. Two hydrogen bonds link A and T while three join G and C

Answer 86

Can be single or double stranded. Different to DNA in its composition in that the sugar ribose replaces deoxyribose and the nitrogenous base Uracil replaced thymine

Answer 87

During metaphase I of meiosis when chromosomes line up at the metaphase plate, there is no force that governs maternal chromosomes to orient themselves towards one pole and paternal chromosomes towards the other. For each homolougous pair, there is a 50% chance that the maternal chromosome will situate itself at a particular pole. Chromosome1 has no effect on the positioning of chromosome 7 - they are independent. Without considering crossing-over, the number of combinations of a daughter cell formed by meiosis of a parent cell with two homologous pairs of chromosomes is four

Answer 88

Means genes for two given traits are linked on the same chromosome and will not follow Mendalian laws for independent assortment. Genes that are close together on the same chromosome are more likely to be inherited together. Genes that are farther apart are more likely to be separated by crossing=over and exchange

Answer 89

The rate at which two genes become unlinked. By establishing this, it is possible to create genetic maps which show the locations of the various alleles on the chromosome

Answer 90

Located on sex chromosomes. The X chromosome is much larger than the Y and carries these genes. As females have two X chromosomes, the dominant sex-linked allele is expressed and the recessive is not. In males any allele on the one X chromosome is expressed

Answer 91

A woman can be heterozygous for a recessive sex-linked disease and act as a carrier. She is not affected but there i a 50% probability that her sons will suffer from the disease. The male X chromosome is passed onlyto female offspring. Therefore an affected male can pass the condition to female but not male offspring. If a daughter is homozygous for the recessive allele she will suffer from the condition. If she is heterozygous, she will act as a carrier

Answer 92

Depict the pattern of inheritance of a particular trait in a family and gives information on gene transfer. Females are represented as circles and males as squares. Solid coloured shapes indicate that an individial has the trait/disease tracked.A dot or partially shaded shape indicates that an individual is a carrier

Answer 93

Many unicellular and some multicellular organisms reproduce via asexual reproduction. The process results in offspring that are genetically identical to the parent. There are three types: 1. Binary fission 2. Budding 3. Fragmentation

Answer 94

Occurs in some single-celled organisms such as bacteria and amoeba. Genetic material within the parent cell is replicated while the cell elongates After the DNA is duplicated, the cell dives in half producing two identical daughter cells.The process is similar to mitosis but the latter involves nuclear disintegration and guidance of chromosomes by microtubules

Answer 95

Yeast cells. Small bud cells are pinched off of from the parent by cell division

Answer 96

eg earthworms and plantsWhereby an organism may become fragmented into multiple pieces. Some or all of these fragments may grow into complete adults

Answer 97

1. Mutations 2. Transformation 3. Transduction 4. Conjugation

Answer 98

Naked DNA from the environment is taken up by the prokaryotic cell and incorporated into its chromosome

Answer 99

Bacteriophages (viruses that infect bacteria) carry pieces of DNA from one bacteria to another

Answer 100

Involves direct one-way transfer of genetic material from one organism to another. The donor extends a sex pilus to the recipient. A cytoplasmic bridge then forms between the two cells. A single strand of DNA from the donor's bacterial chromosome or plasmid is transfered to the recipient. The bridge then breaks and the transferred DNA is taken up by the recipient's bacterial chromosome or plasmid

Answer 101

Combines genetic material from two different sources to create offspring. Specialised germ cells undergo meiotic division and come together to form new individuals with new genetic combinations. Unlike mitosis which produces diploid cells (2N), meosis produces haploid gamete cells (1N). Even greater genetic diversity can be generated as genes are exchanged between chromosomes during crossing over during prophase I or meosis

Answer 102

Have two sets of chromosomes, one from each parent

Answer 103

Have half the chromosome number. Referred to as haploid

Answer 104

The full complement of genetic material includes 22 chrmosome pairs called autosomes which don't differ between the sexes and an additional pair of sex chromosomes. Total of 23 pairs

Answer 105

For example coat colour in rabbits - multiple alleles with varying degrees of dominance determine the resulting coat colour

Answer 106

Traits determined by the additive effect of two or more genes

Answer 107

Affect more than one phenotypic characteristic

Answer 108

Situation in which one allele doesn't completely block the expression of another and alleles blend to form the phenotype. eg petal colour in snapdragons. If red (RR) and white (rr) floering plants are produced, the offspring will have pink flowers (Rr)

Answer 109

Where a heterozygous phenotype expresses both alleles equally. For example, blood types - determined by the alleles IA, IB and i corresponding to different types of antigens in the blood. An individual who is homozygous for IA or IB has an A or B phenotype. An individual who is heterozygous for IA and IB has an AB phenotype

Answer 110

Alternative forms of a single gene. For any inherited trait, an individual possesses an allele from each parent

Answer 111

States that during meiosis, the two alleles from each parent segregate from each other resulting in gametes that each carry one allele for each trait

Answer 112

States that if the two alleles for a trait are different one allele will be dominant (fully expressed in the individual) and the other will be recessive (will not show itself)

Answer 113

The genetic makeup of an organism

Answer 114

Actual physical characteristics of an organism

Answer 115

1, BB x bb 2. Bb x bb 3. Bb x Bb

Answer 116

A 9:3:3:1 ratio is characterisic of crosses between individuals that are either homozygous recessive or homozygous dominant for two different independently assorting traits

Answer 117

After eight weeks of growth, an embryo is known as a fetus

Answer 118

1. In the first few weeks, the placenta and unbilical cord form and become the specialised circulatory system between mother and fetus. This system provides nourushment via oxygenated blood in the unmbilical vein and removes metabolic waste via the umbilical arteries

Answer 119

Develops from two embryonic sacs - the yolk sac ( the site of early blood vessel development) and the allantois (an outpocketing of the gut that contains many blood vessels)

Answer 120

Formed when part of the chorion fuses to the uterine walls. In addition to supplying nutrients and removing waste, prevents toxins and drugs from entering the fetus and functions as an exocrine gland, producing the essential hormones of pregnancy: oestorgen, progesterone and hCG

Answer 121

A membrane that surrounds the amnion

Answer 122

The strong sac that houses the fetus and contains amniotic fluid

Answer 123

~24 hrs after fertilisation, the zygote develops by rapid mitotic cell divisions, the first of which are called cleavages. During the first three divisions, the cells continue to become smaller. ~ day three, the fourth division occurs creating the 16-cell morula

Answer 124

In mammals and other animals along the deuterostome evolutionary line, cleavage is indeterminate, meaning that each cell can develop into a separate organism

Answer 125

Occurs in the protostome evolutionary line (insects, crabs, snails) in which cells specialise early in development

Answer 126

1. As the morula passes from the fallopian tubes into the uterine cavity, fluid penetrates the ball of cells and pushes them to the outer rim, with a small collection of cells at one end of the sphere. 2. The inside of the ball becomes fluid-filled in a process called blastulation. At this stage the embryo is called a blastula or blastocyst and the fluid-filled centre is called the blastocele 3. The blastula develops two specialised parts: the inner cell mass which will later become the embryo, and the trophoblast which will become the placenta 4. The blastula now becomes implanted in the uterine wall and continues to undergo mitotic cell divisions

Answer 127

1. Cleavage 2. From morula to blastula 3. Gastrulation

Answer 128

The cells of the blastulaseparate into three distinct layers: 1. ectoderm - outermost layer 2. mesoderm - middle layer 3. endoderm - innermost layer When the three different layers have become apparent, the assembly is called a gastrula

Answer 129

Gastrulation differs among different embryo types. In amphibians, the ball of cells invaginates to create an inner space, the archenteron which becomes the digestive tract and an opening called a blastopore which becomes the anus In mammals the rapid migration of cells from the ectoderm forms the endoderm and the mesoderm from which structures arise

Answer 130

Later forms: S - sweat glands E - epidermis of the skin E - eye - lens and cornea N - nervous system T - tooth enamel H - hair E - epithelial lining of mouth/rectum N - nails

Answer 131

Later forms: S - skeletal system M - muscle (skeletal) A - adrenal cortex L - lining of the body cavity L - lymphatic system R - Reproductive organs E - excretory system D - dermis of the skin M - muscular layer of the digestive tract C - circulatory system

Answer 132

Later forms: P - pancreas E - epithelial lining of digestive tract T - thyroid R - reproductive tract lining U - urinary tract lining L - liver E - epithelial lining of respiratory tract

Answer 133

Following gastrulation, the nervous system begins to develop. A hollow cord of cells in the mesoderm develops into the notochord which later becomes part of the spinal column. Ectodermal cells above the notochord fuse to become the neural tube which gives rise to the brain and spinal cord. Some ectodermal cells break off the neural tubes and become neural crest cells. These move throughout the body and develop into many parts of the peripheral nervous system such as sensory neurons and glial cells

Answer 134

Sex hormones. Regulate the pattern of male reproduction. Testerone is the most important

Answer 135

In addition to regulating spermatogenesis, accounts for secondary male sex characteristics (pubic hair, facial hair, muscle growth) and determines certain sexual behaviours (sex drive, aggressiveness)

Answer 136

Regulate function of the gonads LH - secreted by the anterior pituitary gland, stimulates the Leydig cells of the testes to produce testosterone FSH - acts with testosterone to continuosly produce sperm

Answer 137

Divided into three main parts: 1. Follicular phase 2. luteal phase 3. menstruation

Answer 138

1. GnRH from the hypothalamus stimulates the anterior pituitary to release FSH and LH 2. FSH and LH trigger the growth of the follicle which begins to produce oestrogen at low levels 3. Oestrogen causes the endometrium to thicken 4. As the amount of oestrogen rises, a positive feedback system causes a surge in LH and FSH 5. A day after the LH surge, ovulation occurs ending the follicular phase

Answer 139

1. LH stimulates the follicle to become the corpus luteum which continues to produce oestrogen and progesterone 2, Endometrial arteries enlarge and glands begin to secrete nutrients

Answer 140

If the egg is not fertilised. the corpus luteum disintegrates resulting in a drop in oestrogen and progesterone causing spasm and rupture of the endometrial arteries, sloughing and menstruation. The follicular phase then begins

Answer 141

The point at which the egg becomes fertilised by a sperm cell. Occurs in the fallopian tubes (or oviducts). The fertilised egg (zygote) then travels via the oviduct to the uterus where it implants on the endometrium and develops into a fetus

Answer 142

The female gonads. Suspended within the abdominal cavity. Composed of hundreds of thousands of follicles, each containing an egg

Answer 143

Begins in the embryo. Oogonia in the ovaries begin the first cycle of meosis stopping at prophase I. 2. These primary oocytes are reactivated by hormones at puberty. FSH encourages development of follicles inducing the completion of the first meotic cycle and begins meiosis II. The unequal division of cytoplasm results in one haploid secondary oocyte, which goes on to from an egg, and one secondary body which can't form a viable gamete 3. Meosis is again halted, this time at metaphase II. 4. Each month from puberty until menopause, one follicle will mature and release its secondary oocyte. If this ovulated oocyte is penetrated by a sperm cell, meosis II is completed resulting in a fertilised egg (a zygote) and a second polar body

Answer 144

The male gonad. Composed of tightly wound seminiferous tubules. Housed outside the abdominal cavity in the scrotum, where they are kept 2 degrees celcius cooler that the rest of the body permitting healthy sperm production

Answer 145

Specialised cells of the seminiferous tubules of the testes. Site of spermatogenesis

Answer 146

Dispersed throughout the seminiferous tubules of the testes. Produce testosterone and other androgens

Answer 147

1. Spermatogonia undergo two cycles of meiosis. After the first, the germ cells are called primary spermatocytes and are still diploid. 2. A second cycle produces haploid secondary spermatocytes 3. These then continue to mature into spermatids. 4, Spermatids then lose their cytoplasmic bridge connections, gain a flagellum tail and become individual sperm cells 5. Spermatozoa then travel along the seminiferous tubules into the epididimus where they become motile 6. From the epididimus, they travel through the vas deferens, ejaculatory duct and urethra. Along the way, secretions from the bulbourethral gland, prostate gland and seminal vesicles create semen

Answer 148

Germ cells produced by the gonads. Have a haploid number of chromosomes (23).

Answer 149

1. Spermatogonia continue to divide mitotically throughout a mature adult's lifetime. Allows a male to produce up to 600 million sperm on a daily basis. Oogonium only divide mitotically in the embryo 2. Oogenesis has resting periods: meosis begins in the embryo and is then halted until puberty. Spermatogenesis begins at puberty and is continuous 3. In oogenesis, cytokinesis is uneven, giving rise to only one viable gamete. Spermatogenesis involves equal cytokinesis and the production of four sperm 4. In spermatogenesis the daughter cells of the meiotic cycle are connected via cytoplasmic bridges until the last stage in development

Answer 150

Unlike the nervous sytem which relies upon electrical impulses to trigger rapid responses, the endocrine system uses chemical signals (hormones) to coordinate longer lasting activities such as growth and reproduction

Answer 151

Brain region that connect the nervous system with the endocrine system. Receives information from nerves throughout the body and initiates an appropriate response, regulating body temp, hunger, thirst etc. Composed of neurosecretory cells that control the activity of the pituitary gland

Answer 152

Sits just under the hypothalamus. Has two parts: anterior (adenohypophysis) and posterior (neurohypophysis)

Answer 153

Secreted by endocrine glands directly into the blood and travel via the circulatory system to their target organs and cells. There are several classes: 1. Steroid 2. Proteins and Peptides 3. Amino acid derivatives

Answer 154

eg oestrogen, testosterone Lipids. Can easily travel through cell membranes to bind with intracellular receptors

Answer 155

eg GH - peptide Cannot traverse the cell membrane but bind to receptors on the cell surface

Answer 156

Each hormone that successfully binds to its receptor activates a series of second messengers which in turn activate multiple enzymes. For this reason, very small amounts of a hormone in the bloodstream can cause dramatic changes in physiology

Answer 157

The main hormone products are: F - FSH L - LH A - ACTH T - TSH - secreted in response to TRH from the hypothalamus

Answer 158

The main hormone products are: P - Prolactin G - GH

Answer 159

Oxytocin and ADH are made in the hypothalamus but are stored and secreted by the posterior pituitary

Answer 160

1. Calcitonin - parathyroid, calcium deposition 2, glucagon - alpha cells of the pancreas 3. insulin - beta cells of pancreas 4. parathyroid hormone - parathyroid, calcium release

Answer 161

Brain and spinal cord

Answer 162

Center of complex neural integration. Composed of three main parts: 1. cerebrum - largest part, controls memory, thought, sensation and movement 2. cerebellum - coordinates and controls movement 3. brainstem - composed of the medulla oblongata, pons and midbrain. Responsible for homeostasis and autonomic functions such as breathing, swalllowing, heart muscle activity and digestion

Answer 163

Has two functions: to relay information to the brain and to process simple stimuli. Primarily integrates by way of reflex a connection of two or three neurons that unconsciously reacts to a simple stimulus eg the knee jerk reaction

Answer 164

Collects and distributes information. Made up of sensory organs, motor (efferent) nerves and sensory (afferent) nerves

Answer 165

Divided into: 1. Somatic - controls skeletal muscle 2. Autonomic - regulates smooth and cadiac muscles and organs of the digestive, CV, urinary and endocrine systems. Can be further divided into sympathetic and parasympathetic

Answer 166

Many impulses come together to make a neuron fire. A single impulse doesn't necessarily trigger the transmission of an action potential. Certain impulses may even have an inhibitory effect

Answer 167

The junction between the axon of a presynaptic neuron and the soma of another neuron or an effector membrane such as muscle. There are two types of synapses: 1. Electric synapses 2. Chemical synapses

Answer 168

Or gap junctions. Protein channels that allow ions to flow freely from one cell to another and thus to function as a unit

Answer 169

Whereby a cell relays an impulse to another cell by converting the impulse into a chemical message, a neurotransmitter

Answer 170

As Na+ rush into the neuron, they cause the electrical potential of the adjacent region to change. The adjacent portion reaches a threshold potential which quickly initiates an AP in theat area. Meanwhile, the original area returns to its resting potential.

Answer 171

1. Diameter - The wider the axon, the greater the speed of the AP 2. Myelination - speed conduction velocity of the impulse. Insulate sections of the membrane so that impulses jump quickly between nodes of Ranvier - saltatory conduction

Answer 172

1. Cell at resting potenial of -40mV 2. Stimulus changes the permeability of the neuronal membrane. Na+ enter making the charge inside the cell more positive 3. Threshold potential reached, opening VGSCs and rapidly increasing charge to +70mV in a small segment of the axon 4. VGSCs close, VGPCs open and resting potential is restored

Answer 173

When a neuron is not active, it is polarised, meaning that the intracellular electrical charge differs from the extracellular charge. The sodium-potassium pump creates this difference in charge by pumping 3Na+outwards for 2K+ inwards. Membrane is also selectively permeable to K+, allowing this to leak outmore readily than Na+ inwards. The result is a negative charge to the inner surface of the cell membrane relative to its outside

Answer 174

1. Sensory neurons (afferents) 2. Interneurons 3. Motor neurons (efferents)

Answer 175

Bundles of axons and dendrites

Answer 176

1, Soma - cell body, contains nucleus and organelles 2. dendrties - extensions of the cytoplasm that carry signals to the soma 3. axon

Answer 177

1. To remove metabolic waste from the body - eg ammonia - highly toxic nitrogenous by-product of cell metabolism. Converted in liver to soluble urea which is then removed by the kidneys 2. To osmoregulate the amount of salts and water in the circulatory system

Answer 178

1. Blood enters via the renal artery 2. Travels via the arterioles into the capillaries 3. A ball of capillaries called the glomerulus is selectively porous allowing water and small solutes such as amino acids, salts and waste products to be filtered out. 4. Red blood cells and plasma proteins continue to circulate through the blood vessels, exiting the kidney via the renal vein

Answer 179

1. The filtrate enters part of the nephron called the Bowman's capsule 2. Travels through the rest of the nephron: the proximal convoluted tubule, the descending and ascending limbs of the Loop of Henle, distal convoluted tubule and the collecting duct 3. Substances are either secreted into the filtrate (H+ to maintain pH) or reabsorbed by the surrounding capillaries (sugars, amino acids, nutrients) 4. The collecting ducts of each nephron open onto a larger opening - the calyx 5. Calyces join the from the renal pelvis, leading into the ureter connecting the kidney to the bladder

Answer 180

Water is reabsorbed from the chyme. Salts are actively transportedmfrom the large intestine and water follows by osmosis leaving dense faeces

Answer 181

Food is broken down in the duodenum Nutrients are reabsorbed in the jejunum and the ileum The lining of the lower small intestine is covered with projections - microvilli - which maximise surface area for diffusion and active transport of molecules The network of blood vessels surrounding the lower small intestine collect the nutrients and transport them to the liver which regulates their release to the heart and other parts of the body

Answer 182

Two glands - the pancreas and the liver - secrete into the duodenum substances crucial for digestion The exocrine pancreas secretes molecules via ducts into the duodenum - hydrolytic enzymes that break down fats, proteins and carbohydrates and a strongly alkaline bicarbonate solution which neutralises the highly acidic chyme This is as opposed to the endocrine pancreas which secretes products (eg insulin) directly into the bloodstream

Answer 183

Two glands - the pancreas and the liver - secrete into the duodenum substances crucial for digestion The liver produces bile, a mixture containing no digestive enzymes but salts and lipids that aid in fat processing. Also contains pigments - by-products of the liver's breakdown of red blood cells

Answer 184

Stores bile until needed

Answer 185

Large muscular organ Capable of storing large volumes of food before moved on to other parts of the digestive system Digestive enzymes and high concentrations of HCl (pH ~2) begin to digest proteins and to break down food into small particles. Food becomes known as the nutrient-rich broth chyme which is slowly released into the duodenum

Answer 186

Throat - passageway that channels food to the oesophagus and air to the trachea

Answer 187

Forces food to the stomach by way of muscular contraction of the oesophageal wall - peristalsis

Answer 188

1. Mechanical breakdown of food by the teeth 2. Saliva is secreted by the salivary glands and increases moisture and begins the chemical breakdown of carbohydrates via the enzyme salivary amylase 3. The tongue manupulates food, pushing the bolus to the pharynx to be swallowed

Answer 189

Bone marrow

Answer 190

Found mainly in the bone marrow Involved with humoral immunity Can specialise into plasma cells

Answer 191

Originate in the bone marrow but travel to the thymus to mature Involved in cell-mediated imune response Are three forms - helper, killer and suppressor T cells

Answer 192

After an large immune response, many memory B and T cells persist in the spleen. Result is permanent immunity After a mild response, there is temporary immunity

Answer 193

1. Macrophages 2. Neutrophils 3. Eosinophils 4. Basophils 5. Dendritic cells

Answer 194

Not very specific. Recognize harmful sequences in virus-infected and cancer cells releasing chemicals that cause these cells to undergo apoptosis

Answer 195

Store histamine Activate an inflammatory response follwoing physical injurt or invasion by pathogens

Answer 196

MHC proteins identify body's own cells. Unique to each individual and occur in every nucleated cell of the body Autoimune diseases occur when the body is unable to discriminate between self and ononself and the immune system attacks it's own cells

Answer 197

1. TB 2. Syphilis 3. Leproust

Answer 198

1. African sleeping sickness 2. Malaria

Answer 199

1. Smallpox 2. Herpes 3. Measles 4. AIDS

Answer 200

Viruses enter the cell and change its biochemistry to produce thousands of viral progeny. Generally uses its own resources to copy its DNA and produce viral RNA Retroviruses eg AIDS contain RNA material. Create an intermediate copy of DNA within the host which is copied to form viral RNA

Answer 201

Link between the circulatory and immune systems There is a net movement of fluid and molecules in the blood from the capillaries to the interstitial fluid. One of the functions of the lymphatic system is to absorb the excess fluid and conduct it in tiny lymph vessels via the lymph nodes to the circulatory system Also plays a crucial role in immunity via production of lymphocytes and transport of WBCs

Answer 202

1. Deoxygenated blood enters the RA via the superior vena cava 2. Tricuspid valve opens allowing blood to enter the RV 3, Blood passes through the pulmonary valve and into the pulmonary artery 4. Blood flows through the pulmonary arteries, arterioles and capillaries. Carbon dioxide is unloaded and oxygen enters the blood 5. Returns to the heart via the pulmonary vein. Enters the LA.

Answer 203

1. Blood enters the LA 2. Via mitral valve, enters LV 3. Forcefully pumped via the aortic valve into the aorta

Answer 204

Maximum pressure attained during arterial pulse

Answer 205

Lowest pressure attained during arterial pulse

Answer 206

55% plasma 45% cells

Answer 207

92% water inorganic salts proteins (eg clotting proteins fibrinogen and prothrombin, immune immunoglubulins, BP regulating albumins) hormones nutrients waste products fats gases

Answer 208

1. 99% RBCs 2. phagocytes 3. lymphocytes 4. platelets - fragments of cells. attach to fibrin at the site of injury to form clots

Answer 209

1. AP triggers the release of stored Ca2+ 2. Ca2+ expose binding sites in the actin filament 3. At these sites, a head of myosin attaches and pulls the thinner actin filament inward - power stroke - ADP and Pi released 4. ATP attaches to the myosin head and triggers its release 5. ATPase on the myosine head cleaves bound ATP. ADP and Pi remains bound to the myosin. Myosin head is now free to reattach to the actin filament 5. The repeated attachment and release of many heads continues as long as there is stimulation or until the muscle fatigues

Answer 210

1. Basic unit is the myofibril composed of thin (predominently three types of actin) and thick (myosin) filaments that slide across each other during muscle contraction. Surrounding these filaments are two types of network - sarcoplasmic reticulum and T-tubules 2. Many closely packed myofibrils make up each fibre. 3. Fibres are surrounded by an endomysium and grouped into fascicles 4. Fascicles are surrounded by perimyceum. Groups of fascicles surrounded by epimyceum make up the total muscle

Answer 211

Attach skeletal muscle to bone or other mucle

Answer 212

Stores Ca2+

Answer 213

Help to conduct nerve impulses

Answer 214

Units of overlapping thin and thick filaments. Single sarcomere is defined from one Z-line to the next.

Answer 215

Alpha actinin, Binds sarcomeres together

Answer 216

Thick (myosin) filaments Overlaps at edges with thin (actin) filaments Is constant during muscle contraction

Answer 217

Area of thick (myosin) filaments that doesn't overlap with actin. Shrinks during muscle contraction

Answer 218

Area of thin (actin) filaments that doesn't overlap with myosin. Shrinks during muscle contraction

Answer 219

1. Skeletal 2. Smooth 3. Cardiac

Answer 220

1. Lacks striations of skeletal muscle 2. Generally not under voluntary control 3. One nucleus per cell

Answer 221

1. Striated 2. Controlled by the autonomic nervous system 3. Between cells, are electrical connections - intercalated discs which relay impulses during a heartbeat 4. One nucleus per cell

Answer 222

1. Striated 2. Composed of two distinct fibre types: red (slow-twitch, contain many mitochondria and myoglobin) and white (fast-twitch, contract with greater force than slow twitch but fatigue more rapidly) 3. Multiple nuclei per cell

Answer 223

Immovable joints eg suture in the skull

Answer 224

1. Synarthroses 2. Amphiarthroses 3, Diarthroses

Answer 225

Cartilagenous joints found throughout the axial skeleton eg between vertibrae Absorb shock

Answer 226

Synovial joints found throughout the appendicular skeleton. Vary in form depending on location Strong, with free movement. Lubricated by synovial fluid

Answer 227

1. Cartilage - At birth most of the skeleton is cartilage. Later replaced by bone in process of endochondral ossification. Bones that don't form from a cartilage template undergo intermembranous ossification 2. Tendons 3. Ligaments - attach bones together at joints

Answer 228

Junction of bone and cartilage in the long bones. Is the location of continued growth of the long bones

Answer 229

1. Cancellous 2. Compact Outer potion of any given human bone is formed from compact bone. The inner portion is cancellous bone

Answer 230

Spongy bone Consists of a network of supporting elements called trabeculae

Answer 231

Composed of dense material made up of structural units called osteons - cylindrical sections at the centre of which is a Haverian canal (tube housing bundles of blodd vessels and nerves). Lamallae - oncentric rings of bony tissue containing osteoblasts surround these canals. Parallel osteons are connected by Volksmann's canals between Haversian canals

Answer 232

1. Long - arms, legs, toes, fingers. Curve slightly to absorb shock and have long ends 2. Short - wrist, ankle. 3. Flat - skull, ribs, hips, sternum, scapula. Broad plates 4. Irregular - vertibrae, parts of the face 5. Sesamoid - eg kneecap. embedded within tendons

Answer 233

Skin. DIvided into dermis and epidermis

Answer 234

Thin outer skin layer composed of stratified squamous epithelial cells - keratinocytes. Undergo progessive maturation through the layers changing shape and becoming filled with keratin. Stratum corneum composed of flattened, dead keratinocytes filled with keratin Has no BVs or nerves Has five layers Also contains melanocytes and Langerhans cells

Answer 235

From outer to innner: 1. stratum corneum 2. stratum lucidem 3. stratum granulosum 4. stratum spinosum 5. stratum basale

Answer 236

Deep skin layer composed of connective tissue including collagen and elastin, sparse cells and ground substance Fibroblasts are the most abundant cell type but there are immune cells including mast cells, lymphocytes and macrophages present Also contains BVs, nerve endings (pacinian, meisner's corpuscles), hair follicles, sweat glands and sebaceous glands

Answer 237

Below dermis. Filled with adipose tissue, BVs, lymphatics and nerves

Answer 238

1. Kingdom 2. Phylum 3. Class 4. Order 5. Family 6. Genus 7. Speces

Answer 239

1. Monera 2. Protista 3. Fungi 4. Plantae 5. Animalia

Answer 240

95% animals are vertibrates. Fall into the phyla Phordata - all have, in some stage of their developement, a notochord, a nerve chord and pharyngeal slits eg humans, fish, reptiles, birds

Answer 241

1. Porifera - spongescellular level of design (no specialised tissues or organs) 2. Cnidarians - corals, sea anemones and jellyfish. Tissue level of design (no organs) 3. Platyhelminthes - flukes, flatworms and tapeworms. Exhibit cephalisation (presence of head and tail regions) 4. Nematoda - roundworms

Answer 242

Have a coelom (lined body cavity that aids in movement, nutrient transport and gamete muturation) at some stage of development 1. Annelidae - segmented worms 2. Arthropoda - includes spiders, insects and lobsters. Characterised by jointed appendages and an exoskeleton 3. Echinodermata - starfish, urchins, sea cucumbers and sand dollars. Have pentaradial symmetry 4. Mollusca - snails, clams and squid. Earliest protostome phylum

Answer 243

Monera - small 1-10um Protista - large - 10-100um Fungi - large - 10-100um Plantae - large 10-100um Animalia - large 10-100um

Answer 244

Monera - prokaryotic Protista - eukaryotic Fungi - eukaryotic Plantae - eukaryotic Animalia - eukaryotic

Answer 245

Monera - absent Protista - present Fungi - present Plantae - present Animalia - present

Answer 246

Monera - nucleoid (single naked circle of DNA) Protista - chromosomes made of DNA, RNA and protein Fungi - chromosomes made of DNA, RNA and protein Plantae - chromosomes made of DNA, RNA and protein Animalia - chromosomes made of DNA, RNA and protein

Answer 247

Monera - absent Protista - sometimes present Fungi - sometimes present Plantae - present Animalia - present

Answer 248

Monera - obligate and facultative anaerobes, obligate aerobes Protista - most obligate aerobes Fungi - most obligate aerobes Plantae - most obligate aerobes Animalia - most obligate aerobes

Answer 249

Monera - if present, enzymes bound to cell membrane. Large variations in metabolic raw materials and end products Protista - if present, enzymes packaged into plastids Fungi - absent Plantae - generally present. Enzymes packaged into chloroplasts Animalia - absent

Answer 250

Monera - many variations Protista - sometimes present Fungi - oxidative metabolism, glycolysis, Kreb's cycle, electron transport chain Plantae - oxidative metabolism, glycolysis, Kreb's cycle, electron transport chain Animalia - oxidative metabolism, glycolysis, Kreb's cycle, electron transport chain

Answer 251

Monera - polysaccharide-amino acid or peptidoglycans Protista - some forms, various types Fungi - chitin Plantae - cellulose Animalia - absent

Answer 252

Monera - rare: conjugation, transduction, transformation Protista - common: fertilisation and meiosis Fungi - common: fertilisation and meiosis Plantae - common: fertilisation and meiosis Animalia - common: fertilisation and meiosis

Answer 253

Monera - autotrophic (photo- or chemosynthesis) and/or heterotrophic Protista - autotrophic (photosynthesis) and/or heterotrophic Fungi - heterotrophic absorption Plantae - autotrophic photosynthesis Animalia - heterotrophic digestion

Answer 254

Monera - bacterial flagellae Protista - undulipodia, ameboid Fungi - flagella only in zoospore gametes. All others non motile Plantae - undulipodia only in some gametes Animalia - undulipodia

Answer 255

Monera - unicellular or colonial Protista - unicellular, multicellular or colonial Fungi - unicellular (yeast) or multicellular Plantae - multicellular Animalia - multicellular

Answer 256

Monera - mostly binary fission. No centrioles, mitotic spindle or microtubules Protista - mitosis. Centrioles, mitotic spindle present Fungi - mitosis. Centrioles, mitotic spindle absent Plantae - mitosis. Centrioles, mitotic spindle absent Animalia - mitosis. Centrioles, mitotic spindle present

Answer 257

Monera - N/A Protista - varies Fungi - spores Plantae - multicellular embryo enclosed in maternal tissues Animalia - blastula

Answer 258

Unlike animls, can continue to grow throughout entire lifetime, This indeterminate growth occurs at the embryonic tissue called the meristem. Primary growthoccurs in the vertical directionvia apical meristemsat the tip of the stem and root. Seconary, lateral, growth occurs at the lateral meristem

Answer 259

Called alternation of generations. In animals the only haploid cells are gametes.In plants, an entire mature haploid organism is part of the life cycle. The haploid generation, called the gametophyte, undergoes mitosis producing gametes which fuse in fertilisation to become a zygote which grows into a mature diploid plant called the sporophyte. The sporophyte undergoes meiosis to produce haploid gametescalled spores. These develop into mature gametophytes

Answer 260

Flowering plants Account for ~90% plants House their reproductive organs within the flower The male reproductive organ is called the stamen and the female the carpel. Pollinisation by wind, animals etc brings the male gametes to the female gametes. Fertilisation occurs, the ovule devlops into a seed and the ovary into a fruit

Answer 261

Heterotrophic but don't ingest their food. Many - detritivores - decompose the organic remains and waste of plants and animals. Some are parasitic. Others are micorrhizae - have a mutualistic, symbiotic relationship with plant roots

Answer 262

Composed of hyphae which form an underground network called the mycelium which may give rise to above-ground fruiting bodies such as mushrooms. Hyphae can be composed of separated cells - separated by cell walls called septa which contain large pores for passage of cytoplasm and organelles from cell to cell. Other Hyphae may have no septa and be composed of one large syncytium of cytoplasm and nuclei - undergo mitosis but not cytokinesis Some fungi have hyphae that can penetrate cell walls of organisms with which they have a parasitic or symbiotic relationship - called haustoria.

Answer 263

Yeast - reproduce by budding. Replicate their genetic material and then pinch off a portion of the membrane and cytoplasm to form a new cell

Answer 264

Can undergo asexual or sexual reproduction depending on environmental conditions. Spend most of their lives as haploid organisms 1. Sexual reproductive cycle begins when one fungi releases hormones which cause the hyphae of the mating fungi to grow toward each other 2. They then fuse ctoplasm - called plasmogamy. 3. Nuclei then fuse in karyogamy creating a diploid organism. 4. This is followed by meiosis creating haploid spores which then grow into mycelium of new organisms

Answer 265

Simply involves mitosis forming clones in the form of spores. These can travel by air, water or flagella in the case of zoospores and can produce new organisms

Answer 266

Used to refer to eukaryotic organisms that are not plants, fungi or animals. Extremely diverse - thought to be the result of endosymbiosis whereby one unicellular organism engulfs another without destroying it Most are unicellular, some are autotrophs, some heterotrophs and others mixotrophs (can be either) Some adhere to asexual reproduction, others engage in some form of sexual reproduction

Answer 267

Include all prokaryotes but there are two distinct groups: bacteria and archaea Three commmon cell shapes are rods (bacilli), spheres (cocci) and spirals Almost all have a cell wall and many also have a capsule that surrounds the cell wall A nucleoid region contains a single circular chromosome with very few associated proteins. Many also contain a smaller ring of DNA - a plasmid - which replicate independently of the cell's chromosome

Answer 268

A key difference is in the structure of the cell wall - ain archaea these contain a variety of polysaccharides and proteins. Bacterial cell walls are composed of peptidoglycans - sugar polymers cross linked by peptide bonds Many archaea - extremophiles have adapted to harsh environments where few other organisms can survive

Answer 269

1. Meiosis I - nuclear membrane disintegrates and homologous chromosomes find each other forming tetrads 2. Chromosomes line up gene by gene, oftentimes cross-crossing to form chiasmata and exchanging genetic materialwith their homologues 3. Homologous chromosomes line up at the metaphase plate and are sparated from each other during anaphase I 4. In some species, nulclear membranes reform during telophase I and cytokinesis completes the division resulting in two haploid cells

Answer 270

The first of two cell divisions then occur during meiosis. Referred to as reduction division because the resultant daughter cells are haploid.

Answer 271

The second cycle of meiosis. Referred to as equatorial division as the haploid cells give rise to more haploid cells

Answer 272

1. No DNA replication occurs before meiosis II but the replication that occured prior to meiosis I created two sister chromatids for each chromosome. In prophase II the nuclear membrane of each daughter cell disintegrates 2. Sister chromatids line up in metaphase II 3. These are pulled apart in anaphase II 4. Nuclear membranes are re-formed in telophase II and cytokinesis completes the formation of four haploid cells

Answer 273

Occurs if cell don't separate properly. Produces one cell with too many copies of a particular gene (polyploidy) and another without any copies (aneuploidy). Down's syndrome is caused by non-disjunction resulting in three copies of chromosome 21

Answer 274

1. Interphase 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase 6. Cytokinesis

Answer 275

1. G1 phase - growth 2. S phase - when chromosomes replicate 3. G2 phase - growth

Answer 276

1. Nuclear envelope begins to disintegrate 2. Chromosomes condense - each consists of two sister chromatids held together by a centromere 3. Microtubules appear forming the mitotic spindle near the centrioles

Answer 277

1. Centrioles gravitate towards opposite ends of the cell 2. Mitotic spindle - composed of microtubules extending from the centrioles - attach to the centromere of each chromosome helping to align the chromosomes in the middle of the cell

Answer 278

1. Chromosomes begin to separate, centromeres split and the spindle fibres pull the chromatids to opposite ends of the cell

Answer 279

1. When the chromatids are at opposite ends of the dividing cell, they become less condensed 2. mitotic spindles disappear 3. Nuclear membranes begin to form in each daughter cell

Answer 280

Usually occurs simultaneously with telophase. The cytoplasm is divided between the two daughter cells. Rearrangements of microfilaments within the cytoplasm creates a cleavage furrow which progress to split the cell into tow distinct daughter cells. The cell membrane develops around the two new cells each containing identical genetic information

Answer 281

In plant cells, cell walls prevent formation of the cleavage furrow. Instead vesicles from the Golgi apparatus carrying components of the new cell wall move towards the midline of the cell. There they coalesce to from the cell plate and a new cell wall is formed.

Answer 282

1. contact inhibition - physical contact with neighbouring cells signals a halt to reproduction 2. Mitogens - chemicals produced by the body. Can stimulat or inhibit cell division

Answer 283

Contain a membrane-bound nucleus and a number of other organells suspended within the protein-rich cytoplasm and mostly surrounded by membranes.

Answer 284

Contains almost all of the cell's DNA Resposible for activities including DNA replication, RNA synthesis and responses to changes in the cell's environment Contains condensed material - chromatin - consisting mainly of DNA and protein May contain one or more nucleoli - specialised areas that rpoduce ribosomal RNA and help to assemble proteins

Answer 285

Small, non-membrane bound particles contisting mainly of rRNA. Contain a small and large subunit. Either bound to the ER membrane or free in the cytoplasm

Answer 286

Highly convoluted bilayer membrane Secretes enzymes and produces other bilayer membranes. Either rough or smooth. Former involved in export of proteins destined to fuse with cell membrane or other organelles. Latter involved in the synthesis of lipids. metabolism of carbohydrates and detoxification of drugs or other toxic substances. Liver cells have abundant amounts of smooth ER

Answer 287

Extensive network of flattened membrane-bound vesicles. Closely linked with the ER. Golgi apparatus and all of its vesicles contain a bilayer membrane. cis face to the Golgi stack receives transport vesicles from the rough ER. Sorts, modifys and stores the ER-made proteins. When ready to be secreted, trans side buds into a vesicle and transports the protein to its final destination. If the protein is to be sectreted from the cell (exocytosis), the vesicle is called a secretory vesicle rather than a transport vesicle

Answer 288

Single-membrane-bound Contain enzymes that create hydrogen peroxide which can catabolize large molecules and toxins. Also contain enzymes that converts the H2O2 into water

Answer 289

Found in plant cells Large membranous sacs that store food, minerals, waste and other chemical products Similar to lysosomes in that they originate from the ER and they carry out hydrolysis Large, central vacuole is enclosed by a membrane called the tonoplast Larger vaculoes arise from coalescence of several smaller ones Can contract and expe water out of a cell or expand and play a role in cellular elongation

Answer 290

Site of many steps of cellular respiration, eg ATP synthesis Composed of a deeply folding inner membrane surrounded by an outer membrane

Answer 291

Contain chlorphyll and other molecules that absorb the radiant energy of sunlight. Drives the light-dependent reactions of photosynthesis. Like the mitochondria, has two membranes. In addition, contains a number of thylakoids - flattened membrane-bound sacs separating the chroloplast into two main spaces: the thylakoid space and the stroma

Answer 292

Support structure of the cell. Network of criss-crossing fibres that maintain and change the cell's shape Composed of microtubules, intermediate filaments and microfilaments

Answer 293

Largest type of fibre that makes up the cytoskeleton Thick, hollow rods found mostly in the cytoplasm Some microtubules within the cytoplasm create tracks along which transport vesicles from the ER and golgi can move Also form cilia and flagella, comprised of nine doublets of microtubules with two single ones at the centre of the structure (9+2 arrangement)

Answer 294

Centrosome is the microtubule organising centre, In some cells may be a pair of centrioles, composed of nine sets of triplet microtubules arranged in a ring Centrosomes and centrioles are the components of the cytoskeleton that play a role in the separation of chromosomes during cell division

Answer 295

Midsize protein fibres Maintain the structural integrity and shape of the cell and the arrangement of organelles within it While microtubules and microfilaments rearrange themselves, intermediate filaments are more permanent The nucleus is ofter surrounded by a network of intermediate filaments holding it in place within the cytosol

Answer 296

Smallest type of fibre Composed of a twisted double chain of actin Assist the cell in changing shape. In muscle cells, are responsible for contraction. In cells that move by crawling along their surface, are responsible for pseudopod formation. Finally, form the cleavage furrow in cell division

Answer 297

No true nucleus or membrane-bound organelles Far simpler and smaller than eukayotic cells. Contain cytoplams bound by a plasma membrane. Within the cytoplasm, genetic material is contained in a dense ball of DNA called the nucleoid. Ribosomes are suspended throughout the cytoplasm. Can also contain pili, cell walls, flagella and output capsule

Answer 298

Formation of biological macromolecules - lipids, proteins, carbohydrates, nucleic acids - requires this. For each covalent bond formed, a molecule of water is lost. Conversely the addition of water molecules t a system can break covalent bonds - hydrolysis reaction

Answer 299

Insoluble in water Many are made up of glycerol and fatty acids (long hydrocabon chains with a carboxyl group at one end) Used as energy store, phospholipids are principal components in cell membranes, steroids such as oestogen and testosterone play key roles in hormonal regulation

Answer 300

Carbon compounds that fit the formula ratio 1:2:1 for carbon, hydrogen and oxygen

Answer 301

eg glucose Individual sugar molecule

Answer 302

eg sucrose Molecule formed forom two joined sugar molecules

Answer 303

eg starch, cellulose, chitin Complex carbohydrates composed of varying numbrs of covalently bound sugar molecules

Answer 304

Functions include structural support (keratin), transport (haemoglobin), movement (actin, myosin) and hormonal coordination (insulin) Large number are enzymes Composed of amino acids linked via peptide bonds to form polypeptide chains

Answer 305

Amino acid sequence

Answer 306

The folding of a polypeptide chain into alpha helices or beta sheets based on hydorgen bonds of the polypeptide backbone

Answer 307

Large-scale folding of the protein involving various forms of bonding resulting in its 3D shape

Answer 308

Binding of number of polypeptide chans together to form a protein's overall shape

Answer 309

DNA and RNA Nucleic acids are composed of chains of nucleotides, each of which is made up of a five carbon sugar ribose or deoxyribose, covalently bonded to a phosphate group and one of five nitrogenous bases

Answer 310

Release energy. Still require activation energy to initiate, eg heat. In living cells, usually provide the energy for endergonic reactions

Answer 311

Require energy

Answer 312

Many enzymes require an additional molecule to function. If this molecule is inorganic, it is a cofactor

Answer 313

Many enzymes require an additional molecule to function. If this molecule is organic, it is a coenzyme. eg vitamins

Answer 314

C6H12O6 + O2 -\> H2O + CO2 +ATP

Answer 315

Takes place in cytosol Exergonic Ten step series of reactions by which 6-carbon glucose converted into 3-carbon pyruvate catalysed by enzymes at each step Releases a small amount of ATP. In the presence of oxygen is followed by the Krebs cycle and electron transport chain in the mitochindria. In the absence of oxygen, products of glycolysis are further fermented into lactate or ethanol but no additional ATP is produced

Answer 316

1. Glucose + ATP -\> glucose-6-phosphate 2. glucose-6-phosphate -\> Fructose-6-phosphate 3. Fructose-6-phosphate + ATP -\> fructose-1,6-diphosphate 4. fructose-1,6-diphosphate -\> 2 x glyceraldehyde-3-phosphate 5. 2 x glyceraldehyde-3-phosphate + 2NAD -\> 2 x 1,3-diphosphoglycerate + 2NADP 6. 2 x 1,3-diphosphoglycerate + 2ADP -\> 2 x 3-phosphoglycerate + 2ATP 7. 2 x 3-phosphoglycerate -\> 2 x 2-phosphoglycerate 8. 2 x 2-phosphoglycerate -\> 2 x phosphoenolpyruvate + 2H2O 9. 2 x phosphoenolpyruvate + 2ATP -\> 2 x pyruvate + 2ATP

Answer 317

2 x pyruvate 2 x ATP 2 x NADH

Answer 318

Takes place in the mitochondrial matrix The two molecules of pyruvate yield 6 x NADH 2 x FADH CO2 GTP

Answer 319

Takes place in the mitochondiral inner membrane High energy products of the Krebs Cycle NADH and FADH2 are passed down a series of electron acceptors (reducing agents), which are then oxidised. Most are proteins including the large protein complexes I, II, II and IV embedded in the membrane and mobile transporters such as the cytochromes The only electron acceptor that isn't a protein is ubiquinone (coenzyme Q) which is a small hydrophobic molecule Oxygen is the final electron acceptor The energy released in this process drives the production of ATP by chemiosmosis Entire process is called oxidative phosphorylation

Answer 320

6H2O + 6CO2 + ATP -\> C6H12O6 + 6O2

Answer 321

Occurs in the chloroplasts Are two main stages: light reactions which occur in the thylakoid membrane and the light dependent Calvin-Benson cycle which occurs in the stroma

Answer 322

1. Chlorophyll in the thylakoid membranes absorbs light energy in the unit of a photon 2. The photon is passed from one to the next pigment molecule until it reaches chlorophyll a 3. The photon first reaches P680 in PSII exciting the chlorophyll's electrons which are captured by the primary electron acceptor leaving the P680 chlorophyll a as a stron oxidising agent 4. A molecule of water is enzymatically split into two electrons (which are supplied to P680), two H+ and an O2- which immediately combines with another to form O2. 5. The electrons that reach the primary electron acceptor are shuttled to PSI via an electron transport chain similar to that of oxidative phosphorylation producing ATP along the way 6. A separate photon excites electrons in P700 of PSI which are captured by its own primary electron acceptor. The electrons shuttled from PSII replace these. 7. The P700 electronscan follow one of two routes noncyclical or cyclical electon flow

Answer 323

Specialised structure which surrounds chlorophyll a There are two main types of light harvesting complex whose chlorophyll a molecules absorb light of slightly different wavelengths - Photosystem II's chlorophyll a is called P680. Photosystem I's chlorophyll a is called P700

Answer 324

Dominant route for electrons from P700 of PSI Electrons are transferred to NADP+ to form NADPH

Answer 325

Electrons from P700 are shuttled back to the electron transport chain producing more ATP but not producing NADPH. This is significant as the Calvin-Benson cycle requires more ATP than NADPH

Answer 326

In the stroma, ATP and NADPH released. Calvin-Benson cycle converts 3 x CO2, 6xATP and 6xNADPH into 6 x glyceraldehyde-3-phosphate one of which exits the cycle and is used for food The remaining 5 molecules are recycled in the cycle using three more molecules of ATP. In summary, for the production of one molecule of sugar, nine ATP and six NADPH are used

Answer 327

Form of potential energy. The potential energy is stored in the bonds between molecules

Answer 328

States that energy can neither be created nor destroyed - also known as the principle of the conservation of energy

Answer 329

When energy is transformed from one form to another, a small amount is lost as unusable energy eg heat Such loss of usable energy increases the disorder, or entropy, of the universe

Answer 330

1. Diffusion 2. Osmosis

Answer 331

Solution containing a lower concentration of solute (water will tend to diffuse into this solution by osmosis)

Answer 332

same concentration of solute

Answer 333

greater concentration of solute

Answer 334

Force generated by the osmotic movement of particles. A cell must balance this (osmoregulation) or will continue to take in water in a hypotonic environment or will continue to lose water in a hypertonic environment