Additional Science Flashcards
Name the 4 cell features shared by both plant and animal
Cell membrane, cytoplasm, nucleus, mitochondria
Name the 3 cell features of only a plant cell
Cell wall, vacuole, chloroplasts
Describe the function of the cell membrane
Separates the content of the cell and its surroundings and controls the movement of substances in and out of the cell
Describe the function of cytoplasm
It is where many of the chemical reactions needed to carry out life processes take place and it also contains organelles
What is the nucleus?
An organelle that contains DNA, it also controls all the activities of the cell
What is mitochondria?
The organelle in which respiration occurs
What is the function of the cell wall
It is made of cellulose to support the cell and allow it to keep its shape
What is the vacuole?
A space in the cytoplasm that is filled with cell sap to help support the plant by keeping the cells rigid
What do chloroplasts do?
They contain chlorophyll that absorbs the light energy used in photosynthesis
When was the electron microscope invented?
1930s
What does the electron microscope do?
It uses beams of electrons to magnify specimens up to about 2000000 times
How did electron microscopes change our understanding of bacteria cells?
Because they showed that bacteria have two kinds of DNA
What is chromosomal DNA?
It is a giant loop of DNA that contains the majority the genetic material
What is plasmid DNA?
It’s smaller loops of DNA that carries extra information
What is the difference between a plant cell wall and a bacteria cell wall?
A bacteria cell wall isn’t made from cellulose and is more flexible
What is the function of flagella?
They are a long, whip-like structure that bacteria can use to move themselves
What do chromosomes contain?
Genetic information
What are chromosomes made from?
A chemical called DNA
What are genes?
Sections of DNA molecules that contain instructions for specific proteins used in the body
What is the double helix?
It is the two strands in the molecule of DNA that are coiled together
What are the two strands in the double helix linked together by?
Bases
Name the 4 bases
Adenine-Thymine
Cytosine-Guanine
What are the matching bases known as?
Complementary base pairs
What are the base pairs joined together by?
A weak hydrogen bond
The ‘back bone’ of DNA is made from what?
Sugar (deoxyribose) and phosphate
On which molecule do the bases join to?
The sugar
Describe the role of Wilkins and Franklin in the discovery of DNA
They were directing beams of X-Ray’s onto purified DNA and used photos to record how the molecule scattered the X-ray and then from this they could work out how the atoms were arranged
Describe the role of Watson and Crick in the discovery of DNA
They used the X-Ray photographs (given to them by Wilkins without Franklins permission) from Franklin and Wilkins to create a 3D model of DNA
Describe the human genome project
It was an international effort that involved scientists in 18 different countries and sharing the data they collected about the human genome
What did the scientists working on the HGP work out?
The sequence of the 3 billion base pairs that make up the human genome which then showed that everyone has 99.9% of DNA in common
Name 5 ways in which the knowledge of the human genome can help medical technologies
Improved testing for genetic disorders
Ways of finding genes that increase risk of certain diseases
New treatments and cures for disorders
Showing evolution as the genome changes over time
Personalised medicines
What is genetic engineering?
The process of removing a gene from one organism and inserting it into the DNA of another
Give an example of a way in which genetic engineering has been used
Scientists have inserted the gene for human insulin into plasmid DNA into bacteria so that the bacteria can produce insulin
What is the name given to organisms that have been genetically engineered?
Genetically modified organisms
Describe how the genetic modification from wild rice to golden rice is beneficial for humans
Golden rice make beta-carotene which is needed by humans to make vitamin A. A lack of Vitamin A can cause death and blindness
Why’re some people worried about the GM rice?
They worry that it will crossbreed with wild rice and contaminate its DNA and others worry that GM food may harm them
What are the advantages and disadvantages of herbicide resistant crops?
Advantages:
Reduces the amount of crop spraying needed by farmers
One large dose of herbicide than lots of small ones
Disadvantages:
Herbicide resistant plants
Loss of biodiversity
Name the advantages and disadvantages of insulin producing bacteria
It can be used by vegans
Supply doesn’t rely on animals anymore
Can be made in vast quantities
Can be made cheaply
Doesn’t suit everyone as there are slight differences
What are the two enzymes used in the genetic modification of bacteria to produce insulin
Cutting enzymes and sticking enzymes
What is a diploid cell?
A cell that contains 2 sets of the 23 chromosomes
What form of cell division occurs for growth or the repairing of damaged cells?
Mitosis
Describe the stages of mitosis
DNA replication occurs so that there are now 4 sets of the chromosomes rather than just 2, the cell then divides and each daughter cell gets one copy of each chromosome, making them identical to each other and the parent cell
What kind of reproduction is mitosis?
Asexual reproduction
Give two examples of asexual reproduction
Bacteria cells often just split in half
Some plants do this by making new plantlets which are initially attached to the, but then split off and grow on their own
What is the name of the other kind of reproduction (not asexual)?
Sexual reproductions
Describe the process of sexual reproduction
This requires two haploid (one set of chromosomes) gametes which fuse during fertilisation to form a diploid zygote which then develops into an embryo
What kind of cell division is needed to produce haploid gametes?
Meiosis
Name the differences between meiosis and mitosis
Meiosis has two cell divisions and thus produces four haploid daughter cells which aren’t genetically identical
Describe the stages of meiosis
DNA replication occurs in the diploid cell so that there are 4 copies of the chromosomes, the diploid divides in two and then in two again to form four haploid cells which aren’t genetically identical as each has different sections of the DNA
What is a clone?
Individuals that are genetically identical
Describe how plants can be cloned
You start with a cutting from the plant which can then be planted and will continue or grow (this is an example of asexual reproduction)
Describes the benefits of cloning
It is useful to make an organism with desirable characteristics
E.g. bulls who produce high quality calves, good sniffer dogs
Can produce individuals with GM traits such as cows who produce insulin in their milk
Describe the drawbacks of cloning
Very low success rate
Can grow orders more quickly and die younger
What are the stages of cloning a mammal?
Removal of diploid nucleus from body cell
Enucleation of egg cell
Insertion of diploid nucleus into enucleated cell
Stimulation to start mitotic division
Implantation into surrogate mother
What is a stem cell?
A cell that can differentiate into different types of cells
Why are embryonic stem cells more useful than adult stem cells?
Because embryonic can differentiate into any cell whereas an adult stem cell is limited to certain types
Why is the use of embryonic stem cells controversial?
Because in the process of extracting the stem cells, the embryo is killed
Describe how a bone marrow transplant works
The patients white blood cells are destroyed and adult stem cells from someone else are put into the patient to produce healthy white blood cells
Why do bone marrow transplants not always work?
Because the body may reject the new cells and destroy them
How could the problem of rejection be solved in bone marrow transplants?
Because they could take a skin cell from the person to create an embryo, the stem cells could then be used to produce cells that make white blood cells and the body would recognise these cells as their own
What is a drawback of embryonic stem cell use?
They could be used to create human clones
What does the base order on the DNA strand form?
The genetic code
What is the process of amino acid chains forming proteins?
Protein synthesis
Where does transcription occur? (In protein synthesis)
In the nucleus
Describe what happens in transcription during the process of protein synthesis
The DNA unzips and the complementary bases to the strand will link together forming a molecule of mRNA
What does mRNA stand for?
Messenger RNA
What are the differences between DNA and RNA?
RNA uses the base Uracil instead of thymine and only has one strand so is therefore small enough to move out of the nucleus into the cytoplasm
After the mRNA leaves the nucleus, where does it attach?
It attaches to a small structure called the ribosome
What is the role of the ribosome?
It moves from one end of the mRNA to the other and decodes the bases in groups of 3 (codons)
What is an amino acid connected to?
transfer RNA
What happens once the ribosome has decoded the mRNA?
The complementary tRNA will line up with the mRNA and releases the amino acid to join the chain
What happens once the amino acid has joined the chain?
The tRNA is released as the ribosome moves onto the next codon
What is a polypeptide?
The chain of amino acids
What happens to the polypeptide once it’s complete?
It can twist, fold up and may link with others to form a protein
What is a protein?
It is a sequence of amino acids
Why do different proteins have different functions?
Because the different sequence results in a specific shape of molecule
Enzymes are ____ to their reaction
Specific
Why are enzymes specific to a reaction?
Because of their shape
What is a mutation?
A change in the sequence bases in the genetic code
Why are some mutations not harmful?
Because some code changes won’t effect the amino acid sequence so the protein shape isn’t affected
What are enzymes sometimes referred to as?
Biological catalyst
Why are enzymes so critical to cell survival?
Because without them, reactions will happen at a too slow rate
Describe how digestion enzymes work?
They help large substances to break apart into smaller ones
How can enzymes help protein synthesis?
They help smaller chemicals to join to make large ones
Describe how DNA replication works
An enzyme will catalyse the splitting apart of the DNA strands and the complementary base pairs will pair up. A different enzyme will then catalyse the joining together of the new bases to make new strands
Why are digestion enzymes used in laundry detergents?
To help digest food and other molecules that stain clothing
Why do proteins, fats and carbohydrates need to be broken down in digestion?
They are too large to pass across cell membranes of the gut into the blood
Describe how fungi digest food
They grow on and through the food, after the enzymes have digested the food, the molecules can then absorb through the cell walls
What is he name of molecules that enzymes work on?
Substrate molecule
Name 3 things that affect rate of reaction (in terms of enzymes)
Temperature
pH
Substrate concentration
What do carbohydrases break down?
Carbohydrates
What do proteases break down?
Proteins
What is the lock and key hypothesis?
It says that the substrate molecule fits tightly into the hole of the active site
What is the active site?
The place that the substrate fits into where the bonds are either broken or created to make the product molecule
What does is mean to denature the active site?
To change the shape of it so much that the enzyme is no longer fit for purpose
What two things can denature the active site?
pH and temperature
How do cells gain energy to power processes?
Respiration
What is the word equation for respiration?
Glucose + oxygen —> Carbon dioxide + Water
What is a capillary,
A tiny blood vessel
Describe how substances move between cells and capillaries
Through a process of diffusion
How does the process of diffusion work?
Particles move from an area of high concentration to low concentration - down the concentration gradient
Where does gas exchange occur?
Between the alveoli and the capillaries in the lungs
Blood enters the lungs with a higher concentration of what?
Carbon dioxide
Describe the net movement of carbon dioxide in gas exchange
It diffuses from the capillaries to the alveolus
Describe the net movement of oxygen in gas exchange
The oxygen diffuses from the alveolus to the capillaries
What is stroke volume?
The volume of blood pumped on each pump
What is the cardiac output?
The volume of blood circulated in a given time
What is the word equation for anaerobic respiration?
Glucose –> lactic acid
What is the need for EPOC?
The oxygen is needed to break down the lactic acid and release energy for the other processes in cells
Through which process do plants manufacture glucose?
Photosynthesis
What is the word equation for photosynthesis?
Carbon dioxide + water —> glucose + oxygen
Where does photosynthesis occur?
In the chloroplasts
What is the light for photosynthesis absorbed by?
Chlorophyll in chloroplasts
Why are leaves broad and flat?
To provide a large surface area for maximum light absorption
What is the role of stomata?
They allow carbon dioxide into the leaf
What other two gases diffuse in and out of the stomata?
Oxygen and water vapour
What do the large air spaces in leaves provide?
A large surface area to volume ratio
What is the importance of a large surface area to volume ratio?
It allows efficient gas exchange
Name the 3 most common limiting factors of plant growth/photosynthesis
Light intensity
Co2 concentration
Temperature
What kind of cells so the surface of roots have?
Root hair cells
What adaptation do root hair cells have that make them useful?
They have a large surface area for substances to enter the root
What is osmosis?
The process in which water molecules move from a high concentration to a low concentration across a partially permeable membrane
What is it called when something absorbs particles against the concentration gradient?
Active transport
What do the xylem tissues do?
They transport water and minerals and also support the plant
What does the phloem tissue do?
They transport sucrose
What is transpiration?
The process where a loss of water through evaporation causes a pull of water and dissolved minerals up through the xylem roots
What is sampling?
Looking at a small portion of an area or population
Why is random sampling likely to be representative of the whole area?
Because every point has an equal chance of being selected
What is a pooter used for?
It is used to catch small invertebrates through an inlet tube by sucking sharply on a second tube connected to a container
Where is a sweep net used?
In areas with long grass
What is a pond net used for?
To sample aquatic habitats
What are pitfall traps used for?
To capture animals that aren’t that active during the day as they can be left overnight
What is a quadrat and what is it used for?
It is a square frame which is randomly placed in an area and the number of plant species found in the quadrat can be counted up, they can be used to estimate total population size
What is systematic sampling?
A method of sampling where the samples are selected from the population at regular or systematic intervals
What are fossils?
Preserved traces or remains of organisms that lived thousands or millions of years ago
What is the fossil record?
The history of life on Earth as shown by fossils from different periods of time
Give 3 reasons why there are gaps in the fossil record
Fossils don’t always form
Soft tissue decays
Many fossils are yet to be found
How does the pentadactyl (five-fingered) limb prove evolution?
Because many organisms share the structure (with variations) which suggests we come from a common ancestor
What is the meristem?
The area just behind the tip of roots and shoots where cells keep divided
What happens after the cells have divided at the meristem?
They elongate
What happens to the cells in the older meristem area?
They differentiate
Why are animals different to plants (in regards to growth)
Because they stop growing when they’re an adult
What are the four components of blood?
Plasma, red blood cells, white blood cells, platelets
What is the role of plasma?
It transports substances such as Co2, food substances and hormones
What is the role of red blood cells?
To transport oxygen to the rest of the body in the form of oxyhemoglobin
Why does the shape of a red blood cell make it beneficial?
It’s a biconcave disc which allows for a large surface area so maximum oxygen can diffuse in and out
What other adaptation does a red blood cell have?
It has no nucleus to make more room for haemoglobin
What do white blood cells do?
Some make antibodies which are proteins that bind to micro organisms that cause disease and destroy them. Others surround and destroy any foreign cells that enter the body
Describe the journey of blood beginning at the vena cava
Vena cava-Right Atrium-Valve-Right Ventricle-Pulmonary Artery-Pulmonary Vein-Left atrium-Valve-Left Ventricle-Aorta
What is the difference between a typical artery and the pulmonary artery?
The pulmonary artery carries deoxygenated blood
What’s the difference between a typical vein and the pulmonary vein?
Pulmonary vein carries oxygenated blood
What are the three types of blood vessel?
Arteries
Capillaries
Veins
Why do arteries have strong thick walls?
Because the blood has to be under high pressure to ensure it reaches all parts of the body
Why do capillaries have such thin walls?
In order to allow for diffusion of substances
Why are veins so wide with a thin muscle layer?
The blood flows relatively slowly under low pressure
What is the alimentary canal?
A muscular tube that runs from mouth to anus
Name the 9 stages/places in the alimentary canal
1) mouth 2) oesophagus 3) stomach 4) small intestine
5) pancreas 6) large intestine 7) anus 8) liver 9) gall bladder
Describe what happens in the mouth
During chewing, the food is broken down to smaller pieces and the tongue helps to form the food into a ball (bolus). Saliva acts as a lubricant to allow ease of swallowing and also begins to break down carbohydrates
What does the oesophagus do
The muscles contract in waves to squeeze the food down to the stomach - this is called peristalsis
Describe what the stomach does
It churns up the food with juices (such as enzymes and acids) and turns the bolus into a thick paste
What is the role of the small intestine?
It contains enzymes to break down food and contains small projections called villi which allow for absorption into capillaries
What does the pancreas do?
Makes digestive enzymes and releases them in to the small intestine
What is the anus for?
Passing undigested food
What does the liver do?
It processes the digested food in the blood plasma (from the small intestine). It also makes bile
What does the gall bladder do?
It stores bile and releases it into the small intestine when needed
What kind of enzyme is amylase and what do it do?
It is a carbohydrase that breaks down starch into simpler sugars which can be broken down by other enzymes into glucose
Where is amylase produced/present?
It is present in saliva. It is also made in pancreas and released into small intestine
What type of enzyme is pepsin and trypsin and where do they work?
They are proteases. Pepsin is made in the stomach and works there and trypsin works in the small intestine
What do lipases do?
They digest fats and break them down to fatty acids and glycerol
What does bile do?
It emulsifies large globules of fat into tiny fat droplets suspended in a watery liquid so they are more easily digested
Where is bile made and stored and why is it stored there?
Bile is made in the liver but stored in the gall bladder. The gall bladder makes it alkaline which helps it to neutralise stomach acid but also produces a slightly alkaline environment for the proteases to work it
Why are the villi so efficient at absorption of food?
Because they make the small intestine have a large surface area and furthermore they have a network of capillaries in each villus which allows for efficient food absorption
What is the problem with people with coeliac disease?
Villi is lost so food absorption is less efficient
What is a functional food?
Foods which claim to make you healthier
What do probiotics contain?
They contain love ‘friendly’ bacteria such as lactobacillus and bifidobacteria
What do lactobacillus and bifidobacteria do?
They produce lactic acid in the gut
What are plant stanol esters?
Oily substances found in plants
Why are plant stanol esters beneficial?
They stop the small intestine from absorbing cholesterol (a substance linked to heart disease)
What are prebiotics?
They are substances that can’t be digested
What are prebiotics beneficial?
Because they act as food for the ‘beneficial’ bacteria in the gut
What are oligosaccharides?
A common form of prebiotic which prevents recurrence of diarrhoea
