my real life gcse wth Flashcards
What is digestion?
Digestion is a process in which large, insoluble molecules in food are broken down into smaller, soluble molecules that can be absorbed into the bloodstream.
What is the alimentary canal?
The alimentary canal is the channel or passage through which food flows through the body, starting at the mouth and ending at the anus.
What are the accessory organs?
Accessory organs produce substances that are needed for digestion to occur (e.g. enzymes, bile) but food does not pass directly through these organs.
Liver - produces bile
Gall bladder - stores and concentrates bile
Pancreas - produces digestive enzymes (lipases, proteases, amylases) to break down food
Salivary glands - produce saliva which moistens food and contains amylase.
What is the function of bile?
Bile emulsifies (breaks down) fats and neutralises stomach acid in the small intestine so that digestive enzymes can function.
What is the role of the mouth in the digestive system?
Mechanical digestion:
- teeth chew food to break it into smaller pieces
- this increases its surface area to volume ratio
- food is shaped into a ball (bolus) and lubricated by saliva so it can be easily swallowed
Chemical digestion:
- amylase enzymes in saliva start digesting starch into maltose
What is the role of the oesophagus in the digestive system?
It is the tube that connects the mouth to the stomach.
Wave-like contractions take place to push the food bolus down without relying on gravity. This process is called peristalsis.
What is the role of the stomach in the digestive system?
Food is mechanically digested by churning while protease enzymes start to chemically digest proteins.
HCl is present to kill bacteria in food and provide optimum pH for protease enzymes.
What is the initial section of the small intestine called?
The duodenem
What is the role of the duodenum in the digestive system?
The digestion of the food exiting the stomach is completed by enzymes that are present in the duodenum lining (secreted by the pancreas)
The pH is slightly alkaline (8-9)
What is the latter section of the small intestine called?
The ileum
What is the role of the ileum in the digestive system?
Where the absorption of water and digested food molecules takes place.
Long and lined with villi (which are lined with microvilli) to increase the SA over which absorption can take place.
What is the role of the large intestine in the digestive system?
Water is absorbed from the remaining material in the colon to produce faeces.
Faeces is then stored in the rectum before exiting the body through the anus.
What is the role of the liver in the digestive system?
Produces bile to emulsify fats and neutralises stomach acid in the small intestine.
Amino acids that are not used to make proteins are broken down, producing urea.
What is ingestion?
The taking in of substances, e.g. food and drink through the mouth
What is mechanical digestion?
The breakdown of food into smaller pieces without chemical change to the food molecules
What is chemical digestion?
The breakdown of large, insoluble molecules into small, soluble molecules.
What is absorption?
The movement of small food molecules and ions through the wall of the intestine into the blood.
What is assimilation?
The movement of digested food molecules into the cells of the body where they are used.
What is egestion?
The passing out of food that has not been digested or absorbed through the anus.
How do you test for the presence of starch?
Method:
1. Place one spatula of the food sample on a dish / 1cm^3 if the sample is liquid
2. Using a dropper, place a few drops of iodine solution onto the food.
3. Record any change in the colour of the solution
Positive result:
Iodine solution goes from yellow/brown to blue/black
How do you test for the presence of sugars?
Method:
1. Place 1cm^3 of the sample and add about 1cm^3 of water to the tube.
2. Add an equal volume of Benedict’s solution and mix.
3. Place the tube in a water bath at about 95°C for a few minutes
4. Record the colour of the solution
Positive result:
Benedict’s solution goes from blue to brick red
How do you test for the presence of proteins?
Method:
1. Place one/two spatulas of the food sample into a test tube or 1cm^3 if the sample is liquid. Add about 1cm^3 of water to the tube.
2. Add an equal volume of potassium hydroxide solution to the tube and stir.
3. Add two drops of copper sulfate solution and stir for two minutes.
4. Record the colour of the solution.
Positive result:
Biuret’s solution goes from blue to purple.
How do you test for the presence of lipids?
Method:
1. Place 1cm^3 of the food sample into a test tube.
2. Add 2cm^3 of ethanol to the tube. Cover the end of the tube and shake the tube vigorously.
3. Allow the contents to settle.
4. Pour the liquid from the top of the mixture into a test tube half-filled with water.
5. Record the colour of the water.
Positive result:
Solution goes from colourless to containing a milky-white emulsion.
What are the two ways in which plants can reproduce? (regarding number of parents)
Sexually and asexually
What are the characteristics of asexual reproduction?
Asexual reproduction only involved one parent and all offspring produced are genetically identical to the parent plant.
What are the different natural methods of asexual reproduction in plants?
- Runners
- Budding
- Tubers
- Bulbs
What are runners and how do they asexually reproduce (plants)?
Some plants grow side branches, known as runners, that have small plantlets at their ends.
Runners are horizontal stems that grow sideways out of the parent plant.
Once they touch the soil, these plantlets will grow roots and the new plantlets will grow and become independent from the parent plant.
How does budding work as a method of asexual reproduction in plants?
A new organism develops as a bud from the parent which then detaches to form a new individual, genetically identical to the parent.
How do tubers work as a method of asexual reproduction in plants?
At first, tubers serve as underground storage organs containing buds which can then develop into new, genetically identical plants
How do bulbs work as a method of asexual reproduction in plants?
Bulbs are storage organs which then mature and become separate plants
What is cutting (reproduction in plants)?
Cutting is an artificial method of asexual reproduction in plants.
Gardeners take cuttings from good parent plants; a section of the parent plant with a new bud is cut off.
This cutting can either be placed into water until new roots grow or can sometimes be placed directly into soil.
Sometimes, the stem of the cutting may first be dipped into ‘rooting powder’, which contains plant growth regulators that encourage new root growth.
These cuttings are then planted and eventually grow into adult plants that are genetically identical to the original plant.
Where are male gametes found (plants)?
Male gametes are found in pollen grains and produced in the anthers of the flower.
Where are female gametes found (plants)?
Female gametes are found in ovules and produced in the ovary of the flower.
What are the sepals and what are their function?
They are the outermost, leaf-like structures of the flower.
Their role is to protect the unopened flower bud.
What are the petals and what is their function?
They are modified leaves, often brightly coloured, that surround the reproductive parts of a flower and collectively form the corolla.
They are often brightly coloured and are scented to attract insects for pollination.
What are the stamens and what is their function?
They are the male parts of the flower consisting of the anther held up on the filament
What are the anthers and what is their function?
They produce male gametes in the form of pollen grains.
What is the stigma and what is its function?
The top of the female part of the flower which collects pollen grains.
What is the ovary and what is its function?
The bottom of the female part of the flower, produces the female gametes.
What is the nectary?
May be present to produce sugary nectar to attract insects.
What is pollination?
Pollination is the transfer of pollen grains from an anther to a stigma. Pollen can be transferred by an animal or by the wind.
Where does fertilisation take place?
Fertilisation takes place inside the ovary when the nucleus of a pollen grain fuses with the nucleus of an ovule to produce a zygote.
Describe the process of pollination and fertilisation.
After pollen has landed on the stigma, it grows a pollen tube down through the style to the ovary.
The nucleus of the pollen grain travels down the pollen tube and fertilises the nucleus in the ovule.
The fertilised ovule develops into a seed. The seed contains the plant embryo, which contains genetic material from both parents. The ovary develops into the fruit.
What happens to the ovule after fertilisation?
The ovule develops into a seed.
What happens to the ovary after fertilisation?
The ovary develops into the fruit.
What are the adaptations of the stigma in a wind pollinated plant?
The stigmas are large and feathery to catch the pollen grains. They also usually have a sticky surface which helps to trap pollen grains that land on them.
What are the adaptations of the petals in a wind pollinated plant?
Petals are typically small, inconspicuous and often absent as they don’t need to attract pollinators.
This also leaves the anthers and stigmas well exposed to the wind.
What are the adaptations of the anthers in a wind pollinated plant?
The anthers hang outside the flower so that pollen can easily be blown away by the wind.
They produce light and dry pollen grains and have versatile attachment to facilitate pollen release.
What is transpiration?
The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
How does water travel from the roots to the leaves?
Water travels up the xylem from the roots into the leaves of the plant to replace the water that has been lost due to transpiration
How is the xylem adapted for its function?
- A substance called lignin is deposited in the cell walls which causes the xylem cells to die
- These cells then become hollow and join end-to-end to form a continuous tube for water and mineral ions to travel through from the roots.
- Lignin strengthens the plant to help it withstand the pressure of the water movement.
What is the function of transpiration?
Transpiration has several functions in plants:
1. transporting mineral ions
2. providing water to keep cells turgid in order to support the structure of the plant
3. providing water to leaf cells for photosynthesis
4. keeping the leaves cool (the conversion of water into water vapour as it leaves the cells and enters the airspace requires heat energy. The using up of heat to convert water into water vapour helps to cool the plant down)
What is the phloem?
The phloem is a complex, living tissue in plants responsible for transporting sugars and other organic compounds, produced during photosynthesis, from the leaves to other parts of the plant.
How is the phloem adapted for its function?
- Made of living cells that are supported by companion cells
- Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)
- Cells have very few subcellular structures to aid the flow of materials.
What is a genome?
A genome is the entire DNA of an organism
What is a gene?
A gene is a section of a molecule of DNA that codes for a specific protein.
What does the nucleus contain?
The nucleus of a cell contains chromosomes on which genes are located.
Describe a DNA molecule.
- Two strands which are coiled to form a double helix
- Contains deoxyribose sugars
- The strands are linked by the following bases: adenine, guanine, thymine, and cytosine
Describe an RNA molecule.
- single stranded
- contains the following bases: adenine, guanine, uracil, and cytosine
What are the stages of protein synthesis?
- Transcription
- Translation
What is protein synthesis?
The process by which cells create proteins
Describe the process of transcription.
When a gene is to be expressed, the base sequence of DNA is copied or transcribed into mRNA.
1. The two strands of the DNA helix are unzipped by breaking the weak hydrogen bonds between base pairs. This unwinding of the helix is caused by an enzyme.
2. The enzyme RNA polymerase attaches to the DNA in a non-coding region just before the gene.
3. RNA polymerase moves along the DNA strand. Free RNA nucleotides form hydrogen bonds with the expose DNA strand nucleotides by complementary base pairing.
Describe the process of translation.
_______________
What is glucose mainly needed for in the body?
Glucose is needed by cells for respiration.
What is insulin?
Insulin is a hormone produced by the pancreas that regulates glucose concentrations in the blood
What happens if the blood glucose concentration is too high?
The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells. In liver and muscle cells, excess glucose is then converted to glycogen for storage.
What is the impact of insulin on the liver?
Causes the liver to convert glucose into glycogen.
What happens if blood glucose levels are too low?
Glucagon is released from the pancreas which triggers glycogen to be turned back into glucose in the liver and released into the bloodstream.
What could cause blood sugar levels to be too low?
Exercising/not eating for a while
What could cause blood sugar levels to be too high?
Consuming sugary or starchy food
What is diabetes?
Diabetes is a condition where the blood glucose levels remain too high.
How can diabetes be treated?
It can be treated by injecting insulin. The extra insulin causes the liver to convert glucose into glycogen, which reduces the blood glucose level.
What is Type 1 diabetes?
Type 1 diabetes is a disorder in which the pancreas fails to produce enough insulin. This can be detected from an early age and is characterised by uncontrolled high blood glucose levels. It is controlled by injecting insulin.
What is Type 2 diabetes?
In Type 2 diabetes, the person’s body cells no longer respond to insulin produced by the pancreas and it is more common in older people. It can be controlled by a carbohydrate controlled diet and an exercise regime. Carbohydrate is digested into glucose which raises the overall blood glucose level.
What is the role of the urinary system?
Removes excess water, mineral ions and urea.
What is selective reabsorption?
The process where the kidneys reabsorb essential substances, like water, glucose, and salts, from the glomerular filtrate back into the bloodstream, while allowing waste products to remain and form urine.
What is the role of the glomerulus?
The glomerulus’s primary role is to filter blood within the kidney’s nephron, separating small molecules like water, salts, and urea from larger molecules like proteins and blood cells, initiating the process of urine formation.
What does not get past the glomerulus?
Red blood cells, most large proteins, glucose
What is Bowman’s capsule?
A cup-shaped structure at the beginning of the nephron, the kidney’s filtering unit, that surrounds a network of capillaries called the glomerulus, where the initial filtration of blood to form urine takes place.
What is a nephron?
The fundamental, microscopic filtering unit within the kidney responsible for forming urine by removing waste products and excess water from the blood.
What does urine contain?
water, urea, mineral ions
When are proteins absorbed (kidneys)?
Proteins are too large to pass through the loop of Henle so are absorbed into the blood.
What is ADH?
Anti-diuretic hormone, released by the pituitary gland
What does ADH do?
ADH causes the kidney tubules to become more permeable which allows more water to be reabsorbed back into the blood.
What happens if there is too much water in the blood?
Hypothalamus detects water level.
Pituitary gland releases less ADH.
Less water reabsorbed by kidneys.
More water lost in urine.
What happens if there is too little water in the blood?
Hypothalamus detects water level.
Pituitary gland releases more ADH.
More water reabsorbed by kidneys.
Less water lost in urine.
What is a population?
A group of organisms of one species, living in the same area at the same time
What is a community?
An interacting group of various species in a common location
What is a habitat?
The place where an organism lives
What is an ecosystem?
The interaction of a community with non-living (abiotic) parts of the environment
What is meant by the term biodiversity?
The range and variety of different species of organisms on Earth, or within an ecosystem
What are some abiotic factors that influence the population size and distribution of organisms?
Abiotic:
- Light intensity
- Temperature
- Moisture levels
- Soil pH
- Wind intensity
- CO2 levels
- Oxygen levels
Biotic:
- Availability of food
- Predators
- Pathogens
How much energy is transferred from one trophic level to the next?
10%
Why is not all energy transferred from one trophic level to the next?
Respiration - energy is lost as heat energy via respiration to enable the movement of an organism
Incomplete consumption - energy may be lost as not all of food may be consumed by an organism (e.g. bones)
Egestion/excretion - energy may be lost due to incomplete digestion, resulting in energy loss via egestion to produce faeces
What are the biological consequences of pollution of air by sulfur dioxide and carbon monoxide?
- Acid rain leaches minerals and nutrients out of the soil, causing death of plants and trees
- Acid rain damages the waxy layer of leaves, reducing ability of plants and trees to absorb mineral ions needed for growth
- Acid rain acidifies rivers and lakes, resulting in death of aquatic organisms
- Acid rain corrodes metals and limestone in buildings
- Carbon monoxide may cause constant tiredness due to poor oxygen transport
- Carbon monoxide may cause emphysema due to insufficient oxygen via aerobic respiration
- If pregnant, carbon monoxide may result in insufficient for respiration, hindering growth of foetus
What are the greenhouse gases?
water vapour, carbon dioxide, nitrous oxide, methane and CFCs
How do human activities contribute to greenhouse gases?
CO2 - produced during combustion of fuels in industrial processes, produced in car exhausts
Nitrous oxide - released from fertilisers in farms, released from cattle waste in farms, produced from combustion of fossil fuels in vehicle engines
Methane - released from rice paddy fields, released from cattle
CFC - used in fridges and released into the atmosphere when disposed, used in aerosol sprays
What is the greenhouse effect?
- The Sun sends short-wave radiation to Earth
- The Earth absorbs it and re-emits it as long-wave heat
- Greenhouse gases trap some of this heat in the atmosphere
- This keeps the Earth warm enough for life
What is a synapse?
The junction between two neurones
What is the structure of a synapse?
- One end (presynaptic membrane) contains vesicles that contain neurotransmitters
- The other end (postsynaptic membrane) has neurotransmitter receptor molecules
- The space between the two is called the synaptic cleft
What happens when an electrical impulse crosses a synapse?
- The electrical impulse travels along the first axon
- This triggers the nerve-ending of the presynaptic neuron to release chemical messengers called neurotransmitters from vesicles which fuse with the presynaptic membrane
- The neurotransmitters diffuse across the synaptic gap (or cleft) and bind with the receptor molecules on the membrane of the second neurone (known as the postsynaptic membrane)
- This stimulates the second neuron to generate an electrical impulse that travels down the second axon
- The neurotransmitters are then destroyed to prevent continued stimulation of the second neuron which would cause repeated impulses to be sent
- Synapses ensure that impulses only travel in one direction, avoiding confusion within the nervous system if impulses were travelling in both directions
- As this is the only part of the nervous system where messages are chemical as opposed to electrical, it is the only place where drugs can act to affect the nervous system
What is an agonist?
Agonists stimulate specific receptors which decreases the number and sensitivity of the receptors. As the sensitivity has decreased, an individual must take more of the drug to trigger the receptors and therefore feel the effects
What does repeated use of agonist drugs lead to?
Drug tolerance
What is an antagonist?
Antagonists block specific receptors which increases both the number and sensitivity of these receptors. This sensitisation leads to the individual craving more of the drug
What does repeated use of antagonist drugs lead to?
Drug addiction
How are bacteria genetically modified to produce more insulin?
- Restriction enzymes cut out the insulin gene from the human DNA
- A plasmid is removed from the DNA and restriction enzymes cut it
- A different enzyme causes the plasmid and insulin gene to join together by base pairing
- Bacteria containing the insulin gene reproduce rapidly inside bioreactors
Describe the effect of a named virus that infects plants.
Tobacco Mosaic Virus (TMV) - affects tobacco, infects the chloroplasts, changes the colour of the plant from green to yellow, hinders the plant’s ability to photosynthesise
Describe the effect of a named bacteria that infects plants.
Agrobacterium tumefaciens - causes crown gall disease in plants, resulting in the formation of tumors on the roots and stems
Describe the effect of a named virus that infects humans.
HIV (human immunodeficiency viruses) - causes AIDS which affects the human immune system by attacking and destroying white blood cells, making the body vulnerable to various infections and diseases
Describe the effect of a named bacteria that infects humans.
Mycobacterium tuberculosis - responsible for tuberculosis which primarily affects the lungs, causing a chronic cough, potentially bloody mucus, and damage to lung tissue
How do bacteria and fungi obtain energy from dead organic matter?
Bacteria and fungi break down dead plant and animal matter. They secrete enzymes on the surface of the dead organisms to break the organism down and then absorb the digested, smaller food molecules
