Biology Flashcards
What is the difference between Glycogen, Glucose, Glucagon and Glycerol.
Glucose: Sugar
Glycogen: Carbohydrate - how glucose is stored in animals
Glycerol: Breakdown product of lipids
Glucagon: Hormone that brings super levels back up (it does the opposite of insulin
What is the difference between a prokaryote and a eukaryote?
Prokaryotic cells = Bacterial cells:
Much smaller in comparison.
They have cytoplasm and a cell membrane surrounded by a cell wall.
The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids.
Eukaryotic cells = Animal cells and plant cells
Bigger than bacterial / prokaryote cells
Genetic material enclosed in a nucleus
Have a cell membrane and cytoplasm
What do animal cells have and what are these sub cellular structures’ functions?
Cytoplasm - Where chemical reactions happen
Nucleus - Contains DNA
Mitochondria - Respiration
Ribosomes - Protein synthesis (making of protein)
Cell membrane - Controls what goes in and out of the cell
What do plant cells have that animal cells don’t have?
Chloroplasts containing chlorophyll
Cell wall made of cellulose
Permanent vacuole filled with cell sap
What is the cell wall made of?
Cellulose
What is the function of chloroplasts?
Photosynthesis - to make glucose
Are able to absorb sunlight energy
Chlorophyll
What happens in the growth phase of the cell cycle?
Genetic material is doubled
It increases the number of sub-cellular structures such as ribosomes and mitochondria.
What happens once the growth phase is completed?
Mitosis - cell division.
Describe the overall process of mitosis.
- Chromosomes have been duplicated during the growth phase
- Nuclear membrane breaks down
- Chromosomes can align along the centre of the cell
- Sister chromatids are torn apart and pulled to opposite poles of the cell
- Cytokinesis happens - the cell divides into two cells
Describe the products of mitosis?
x2 genetically identical, diploid daughter cells
Why is mitosis important?
Growth and repair
What is the definition of a stem cell?
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
Where can stem cells be found in humans?
Embryos
Adult bone marrow contains stem cells that can differentiation into blood cells (red or white)
Where can stem cells be found in plants?
Meristem - stem cells here can differentiate into any type of plant cell, throughout the life of a plant
Why are we interested in stem cells?
Because treatment with stem cells may be able to help conditions such as diabetes (by producing new pancreas cells that can make insulin) and paralysis (by producing new nerve cells).
What is therapeutic cloning?
In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
What are some of the hesitations of using stem cells?
The use of stem cells has potential risks such as transfer of viral infection
Some people have ethical or religious objections.
Describe some of the uses of plant stem cells from meristems.
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
Rare species can be cloned to protect from extinction.
Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
What is the definition of diffusion?
Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration.
What factors affect the rate of diffusion?
Temperature
Concentration gradient
Surface area to volume ratio
(Diffusion distance)
Why do multicellular organisms require transport systems but unicellular organisms do not?
A single-celled organism has a relatively large surface area to volume ratio. This allows sufficient transport of molecules into and out of the cell, by diffusion, to meet the needs of the organism.
Multicellular organisms have a low surface-area to volume ratio so they require transport systems.
Explain how the lungs are adapted for gas exchange.
There are millions of alveoli. The alveoli increase the surface area to volume ratio of the lungs which increases the rate of diffusion.
The wall of the alveoli and the blood capillaries are one cell thick, reducing the diffusion distance
A steep concentration gradient is maintained because the wall of lungs have a very rich blood supply.
Explain how the small intestine are adapted for nutrient absorption.
There are millions of villi. The villi increase the surface area to volume ratio.
The wall of the villi are one cell thick, reducing the diffusion distance
A steep concentration gradient is maintained because the small intestines have a very rich blood supply.
What is the definition of osmosis?
Water may move across cell membranes via osmosis. Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
What is the definition of active transport?
Give two examples of uses of active transport.
Active transport moves substances from an area of low concentration to an area of high concentration, against a concentration gradient, using energy from respiration.
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil. Plants require ions for healthy growth.
It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
What is the difference between a cell, a tissue, an organ and an organ system?
Cells are the basic building blocks of all living organisms.
A tissue is a group of identical cells with a similar structure and function.
Organs are aggregations of different tissues performing specific functions.
Organs are organised into organ systems, which work together to form organisms.
Where is amylase made?
Salivary glands, mouth
Pancreas
Small intestine
Where is lipase made?
Pancreas
Small intestine
Where is protease made?
Stomach
Pancreas
Small intestine
What does lipase do?
Lipase breaks down lipids into 3x fatty acids and glycerol
Lipid —> Fatty acids x3 + Glycerol
What do proteases do?
Proteases break down protein into amino acids
What do carbohydrases do?
Carbohydrases break down carbohydrates to simple sugars.
What does amylase do?
Amylase is a carbohydrase which breaks down starch.
Where are all 3 types of digestive enzymes made?
All 3x are made in the Small intestine and Pancreas
Stomach also makes protease
Mouth also makes amylase
What is the role of bile in digestion?
It is alkaline to neutralise hydrochloric acid from the stomach.
It also emulsifies fat: breaks down large lipid droplets into small lipid droplets which increases the surface area:volume ratio. This is to help lipase work faster.
The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
Where is bile made and stored?
Bile is made in the liver and stored in the gall bladder.
The heart is an organ that pumps blood around the body in a double circulatory system. What does this mean?
Two circuits:
heart —> lungs —> heart
heart —> body —> heart
What are the three types of blood vessels?
Vein - wide lumen, valves
Artery - narrow lumen, thick wall (muscle, elastic fibres)
Capillary - thin, one cell thick wall
How are the arteries adapted for their function?
Thick walls made of muscle and elastic fibres.
The muscle helps the arteries withstand high blood pressure.
The elastic fibres allow the arteries to stretch and recoil.
They have a narrow lumen, maintaining high blood pressure.
How are the capillaries adapted for their function?
Their walls are only one cell thick - super thin, to allow a short diffusion distance, to speed up the rate of diffusion and active transport of substances across their walls.
How are the veins adapted for their function?
Thin walled, with very wide lumen. The wide lumen lowers the resistance to the blood flow.
They have valves to prevent backflow of blood.
What controls the natural resting heart rate?
A pacemaker in the right atrium of the heart.
Sinoatrial Node: The natural pacemaker that sits in the right atrium in the heart and controls the heart rate, by making the heart contract when it releases an electrical signal
Describe the 4 components of blood
Red blood cells
White blood cells
Platelets
Plasma
What is the role of the plasma?
Transport of carbon dioxide, digested food, urea, hormones and heat energy.
How are red blood cells adapted for their function?
Function of RBCs: Transport oxygen around the body
Biconcave shape - increases its surface area to volume ratio
Absence of nucleus - more space to fit more haemoglobin in
Presence of haemoglobin - this is what the oxygen binds to
What is function of platelets?
Platelets cause blood clotting - to prevent blood loss and prevent the entry of pathogens.
What are the two types of white blood cells?
Lymphocytes - Produce antibodies and antitoxins
Phagocytes - Engulf (eat and digest) pathogens
What do antibodies do?
Antibodies bind to the antigen on the pathogens to help destroy them.
What are the different tissues in a plant, in order from top of the leaf to the bottom of the leaf.
Waxy cuticle = Prevent water loss by evaporation
Upper epidermis
Palisade mesophyll = Photosynthesis, so it’s packed with chloroplasts
Spongy mesophyll (= Gas exchange, so it has airspaces) + xylem + phloem
Lower epidermis - stomata, guard cells
What is the function of the palisade mesophyll?
What is the function of the spongy mesophyll?
What is the function of the xylem?
What is the function of the phloem?
What is the function of the guard cells?
What is the function of the palisade mesophyll?
Photosynthesis - Therefore it’s packed with chloroplasts with chlorophyll
What is the function of the spongy mesophyll?
Gaseous exchange - Therefore it has air spaces, creating a high surface area to volume ratio
What is the function of the xylem?
Transport of water and dissolved mineral ions, from the roots to the rest of the plant.
What is the function of the phloem?
Transport of sucrose and amino acids, from the leaves to the rest of the plant.
What is the function of the guard cells?
They surround the stomata, and open or close them. They open to allow the movement of carbon dioxide and oxygen in and out of the leaf. They might close to prevent water loss.
What is the definition of a pathogen?
Pathogens are microorganisms that cause infectious disease. Pathogens may be viruses, bacteria, protists or fungi. They may infect plants or animals and can be spread by direct contact, by water or by air.
How do bacteria and viruses make us ill?
Bacteria and viruses may reproduce rapidly inside the body.
Bacteria may produce toxins that damage tissues and make us feel ill.
Viruses live and reproduce inside cells, causing cell damage.
What is (TMV) Tobacco Mosaic Virus? What does it do?
Tobacco mosaic virus (TMV) is a widespread plant pathogen affecting many species of plants including tomatoes. It gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to lack of photosynthesis.
What is Measles?
What does it do?
How does it spread?
How can its spreads be prevented?
Virus
Symptoms: Fever and a red skin rash - can be fatal if complications arise.
Prevention: Young children are vaccinated against measles.
Spread: Inhalation of droplets from sneezes and coughs.
What is HIV? What are its symptoms? How does it spread?
Virus, Human Immunodeficiency Virus
Symptoms: HIV initially causes a flu-like illness. Unless successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells. Late stage HIV infection, or AIDS, occurs when the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers.
Spread: Exchange of body fluids such as via sexual contact or when drug users share needles.
What is Salmonella? How is it spread? How can it spread be prevented? What are its symptoms?
Bacteria
Spread: Food poisoning is spread by bacteria ingested in food, or on food prepared in unhygienic conditions.
Prevention: In the UK, poultry are vaccinated against Salmonella to control the spread.
Symptoms: Fever, abdominal cramps, vomiting and diarrhoea
What is Gonorrhoea? What are its symptoms? How does it spread? How can its spread be prevented?
Bacterial
Spread: Sexually transmitted disease (STD)
Symptoms: Thick yellow or green discharge from the vagina or penis and pain on urinating.
Treatment: Antibiotic penicillin until many resistant strains appeared.
Prevention: Treatment with antibiotics or the use of a barrier method of contraception such as a condom.
What is Rose black spot? What are its symptoms? How does it spread? How can its spread be prevented?
Fungus
Symptoms: Purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced.
Spread: Water or wind.
Treatment: Fungicides and/or removing and destroying the affected leaves.
What is Malaria? What are its symptoms? How does it spread? How can its spread be prevented?
The malarial protist has a life cycle that includes the mosquito.
Symptoms: Malaria causes recurrent episodes of fever and can be fatal.
Prevention: The spread of malaria is controlled by preventing the vectors, mosquitos, from breeding and by using mosquito nets to avoid being bitten.
What are the non-specific defence systems the human body has to pathogen from entering the body?
- Skin
- Acts as a barrier
- Mucus and cilia in the trachea and bronchi
- Mucus is sticky and traps pathogens
- Cilia wafts the mucus up the airways to the back of the throat, where the mucus is either swallowed or coughed out
- Stomach has hydrochloric acid
- Destroys pathogens
- Nose hairs in the nose
- Prevent the entry of pathogens
How does the immune system try to destroy pathogens if they enter the body?
- Phagocytes engulf and digest the pathogens
- Lymphocytes produce antibodies which bind to the antigens on pathogens, which helps their destruction
- Lymphocytes also produce antitoxins which neutralise toxins produced by bacteria
How do vaccines provide immunity?
They inject a dead or weak, inactive form of the pathogen.
This stimulates an immune response, and so lymphocytes produce antibodies to attack the pathogen.
Memory lymphocytes are also produced.
If in the future that person is exposed to that same pathogen, their memory lymphocytes can make the antibodies…
- sooner
- faster
- in bigger amount
… killing the pathogen before it has time to make the person ill.
What are antibiotics used for?
To kill bacteria inside the body.
Specific bacteria need specific antibiotics.
Why is it difficult to produce a drug that kills viruses?
Viruses live inside host (human) cells. A drug that kills a virus would have to kill the host’s own cell. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues.
Describe the use of painkillers.
Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens.
What is eutrophication?
What two gasses cause acid rain?
Sulphur dioxide
Oxides of Nitrogen
How are oxides of nitrogen formed?
Nitrogen and Oxygen naturally exist in the air. In car engines it can get so hot that the Oxygen and Nitrogen actually react together to form Oxides of Nitrogen. Oxides of Nitrogen cause acid rain.
How is sulfur dioxide formed?
Combustion of sulfur impurities in hydrocarbon fuels results in the formation of sulfur dioxide.
What is peat and what are the consequences of its destruction?
Peat bogs are the result of thousands of years of plant water that has been unable to decay fully due to acidic conditions and a lack of oxygen. They are very wet areas of land without trees in which many types of moss grow. They are acidic and often have very low levels of nutrients. Here decomposition is very slow and peat is formed from partially decayed plants. Peat is a very useful fuel and is also a natural compost. When it is burned or it decays it releases carbon dioxide into the atmosphere, adding to air pollution. Peat bogs also provide habitats to many different species of plants, animals and microorganisms, so their destruction (either for the land or for the peat itself) is reducing biodiversity.
For many years peat was removed from bogs for gardeners to add to their soil or to burn as fuel. This dramatically reduced biodiversity. Because peat takes such a long time to form, it is a non-renewable energy resource like fossil fuels.
Peat bogs are a very important store of carbon. We call them carbon sinks. If all the peat was removed and burned this would quickly release a huge volume of carbon dioxide into the atmosphere and contribute to the greenhouse effect.
Explain how global warming has an impact on biodiversity.
Ice caps may melt, increasing sea levels and flooding lowlands. This could destroy habitats so reducing biodiversity.
Organisms may be able to live in alternative countries or be excluded from other due to temperature changes.
The migration of birds, mammals etc may be affected.
If animals an plants cannot adapt to the new conditions they may be threatened with extinction, reducing biodiversity.
Describe three sources of pollution.
Pollution can occur:
- in water, from sewage, fertiliser or toxic chemicals
- in air, from smoke and acidic gases
- on land, from landfill and from toxic chemicals.
How is biomass lost from one energy level to the next?
- Light reflects off plants or misses the plants completely.
- Some light energy heats up the plants.
- Not all parts of an organism are eaten e.g. roots and bones.
- Some biomass is lost as waste. Some of the food consumed cannot be digested so is lost as faeces. N.B Decomposers can utili thhe biomas, but they do not normally appear in food chains or pyramids.
- Lots of the biomass is used for respiration so it is not available to be passed along the food chain. The energy released is used for movement, heating the body etc and some is lost to the environment.
What is food security?
Which factors affect food security?
Food security is having enough food to feed a population.
Biological factors which are threatening food security include:
- Increasing birth rate
- Changing diets in developed countries means scarce food resources are transported around the world
- New pests and pathogens that affect farming
- Environmental changes that affect food production, such as widespread famine occurring ins one countries if rain fails
- The cost of agricultural inputs
- Conflicts that have arisen in some parts of the world which affect the availability of water or food.
Describe and evaluate the advantages and disadvantages of modern farming techniques.
- Livestock raised in small pens and cages means
- Adv: Livestock use less energy for movement, leaving more energy available for growth
- Dis: Keeping animals confined in such small spaces is seen as unethical by many people. Disease can spread easily as many animals are kept very close together.
- Livestock fed antibiotics in their food.
- Adv: Antibiotics prevent diseases and bacterial infections in livestock.
- Dis: Scientists think this may be leading to antibiotic resistant in bacteria.
- Monocultures
- Adv: Farmers only grow a single crop type across a vast areas of land as this maximises the amount of food produced and their profits.
- Dis: Monocultures only support a low level of biodiversity.
- Fertiliser use
- Adv: Increases plant growth and therefore maximises food production.
- Dis: Runoff occurs from agricultural land if fertilisers are applied in too high a concentration causing fertilisers to enter watercourses which can lead to eutrophication and eventually the death of aquatic systems.
- Hedgerow removal
- Adv: This has made fields bigger and easier to maintain with big farm machinery.
- Dis: Reduces biodiversity as hedgerows provide a habitat for al larger number of species.
What is coronary heart disease?
In coronary heart disease layers of fatty material build up inside the coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle.
How are stents useful in coronary heart disease?
Stents are used to keep the coronary arteries open.
How are statins useful in coronary heart disease?
Statins are widely used to reduce blood cholesterol levels which slows down the rate of fatty material deposit.
What is the definition of health?
State of physical, mental and social well-being and not merely the absence of disease.
Can you give some examples of how different types of diseases can interact.
- Defects in the immune system mean that an individual is more likely to suffer from infectious diseases.
- Viruses living in cells can be the trigger for cancers.
- Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma.
- Severe physical ill health can lead to depression and other mental illness.
What is the difference between the daughter cells formed in meiosis and mitosis?
Mitosis
- 2 daughter cells
- Diploid chromosomes
- Genetically identical
- For growth and repair
- Happens all over the body
Meiosis
- 4 daughter cells
- Haploid chromosomes
- Genetic variation
- For producing gametes
- Happens in reproductive organs - ovaries, testes
What is the difference between the offspring in asexual versus sexual reproduction?
In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
What is the definition of genome?
The genome of an organism is the entire genetic material of that organism.
Describe the structure of DNA.
DNA is a polymer made up of two strands forming a double helix.
The DNA polymer is made up of repeating nucleotide units.
The long strands of DNA consist of an alternating sugar-phosphate backbone
The DNA is contained in structures called chromosomes, which contains lots of genes within them.
The monomer of DNA is a nucleotide, which consists of a sugar, phosphate and one of four bases, A, C, G and T..
What is a gene?
A gene is a small section of DNA on a chromosome.
Each gene codes for a particular sequence of amino acids, to make a specific protein.
Describe how DNA codes for a particular protein.
A sequence of three bases is the code for a particular amino acid.
The order of bases controls the order in which amino acids are assembled.
The sequence of the amino acids, results in the formation of a particular protein.
The sequence of bases decides the sequence of amino acids which decides the protein made.
Describe the process of protein synthesis.
The base code of each gene is transcribed onto a messenger RNA (mRNA) molecule.
mRNA moves out of the nucleus and attaches to a ribosome (the mRNA acts as a messenger between DNA and the ribosome)
The correct sequence of amino acids are then brought to the ribosome and joined together
This amino acid sequence then is folded into a protein
Why is it important for us to try understand the human genome
Search for genes linked to different types of disease
Understanding causes and treatment of inherited disorders
Use in tracing human migration patterns from the past
Describe how genetic variants in non-coding DNA could alter the phenotype?
A mutation can occur in a section of non-coding DNA that controls gene expression i.e. can switch genes on or off, or just alter gene expression.
What are the different types of mutations?
Deletion = A C G G T A —> A C G T A
Insertion = A C G G T A —> A C G A G T A
Substitution = A C G G T A —> A C G A T A
List different abiotic factors which can affect a community.
Abiotic (non-living) factors which can affect a community are:
- light intensity
- temperature
- moisture levels
- soil pH and mineral content
- wind intensity and direction
- carbon dioxide levels for plants
- oxygen levels for aquatic animals.
Describe how a change in DNA structure can lead to a change to the protein?
If there is a change in the order of the bases in a section of DNA (eg. in a gene), then a different protein may be produced. This protein may not function in the same way as the original protein would have (before the change occurred in the DNA)
List different biotic factors which can affect a community.
- availability of food
- new predators arriving
- nnew pathogens
- one species outcompeting another so the numbers are no longer sufficient to breed.
