Biology B1-B3 Flashcards
What is a eukaryotic cell? (3 points)
A cell that contains its genetic material in a nucleus
Relatively large and complex
Plants and animal cells are eukaryotic
What is a prokaryotic cell? (3p)
Genetic material floats around in cytoplasm
Relatively small
Bacterial cells are prokaryotic
What is the structure of DNA? (2p)
A polymer made of many nucleotide monomers
Made of 2 strands in the shape of a double helix
Describe the structure of a nucleotide
Contains a phosphate, deoxyribose and a base
What is mRNA?
A copy of DNA strand
Used for the production of protein
Describe transcription (3p)
The DNA is unzipped
The complementary mRNA nucleotides bind to their respective DNA nucleotides
mRNA detaches and leaves the nucleus
Describe translation (3p)
mRNA produced in transcription travels to a ribosome
Carrier molecules carry amino acids to the ribosome based on the mRNA sequence
The amino acids are joined together, making a protein.
What are enzymes?
Catalysts that speed up the rate of metabolic reactions
Describe the structure of enzymes
Enzymes are proteins that contain an active site that fits a specific molecule, called a substrate
Describe the lock and key hypothesis (3p)
The enzyme fits into the substrate much like a key
The substrate only fits that enzymes, much like a lock
This hypothesis states that a specific enzyme can onpy bw used for a specific substrate, like a lock and a key
What factors affect enzyme reaction? (3p)
pH-An enzyme has an optimum pH. Once it reaches the optimum pH the enzyme may unfold, making it become
denatured
Substrate concentration- the higher the substrate concentration, the higher the rate of reaction. However, at some point the enzyme molecules will bound to ALL the substrate molecule
Enzyme concentration this is the same as of substrate concentration
How does temperature affect enzymes (2p)
As temperature increases, the enzyme and substrate molecules move faster, thus increasing the reaction rate
However, if the temperature passes the optimum temperature, the amino acids in the enzymes break apart, changing the shape of the enzyme, meaning it no longer works
What are carbohydrates?
Some carbohydrates are polymers
They are made from smaller carbohydrate molecules such as sugars
What enzyme breaks down carbohydrates and what is it broken down into? (2p)
Carbohydrase
Sugar molecules
What are proteins? (2p)
Proteins are polymers
Made from amino acids
What enzymes break down proteins and what is it broken down into? (2p)
Protease
amino acid molecules
What are lipids? (2p)
Lipids are the fats and oils you eat
Lipids are synthesized from three fatty acids and one glycerol molecules
What enzymes break down lipids and what is it broken down into? (2p)
Lipase
Fatty acids and glycerol
What is the purpose of respiration?
Supplying the body with oxygen needed for energy transfer
What type of reaction is respiration?
Exothermic
What is the equation for aerobic respiration?
Glucose + Oxygen -> carbon dioxide + water
C6H12O6 + 6O2 -> 6CO2 + 6H2O
What energy store is transferred to in respiration?
ATP
What is ATP used for? (3P)
To synthesize larger molecules from smaller ones to make new cell material
For movement- ATP is used to contract muscle cells
To stay warm- ATP increases the rate of respiration, transferring more energy by heating
Where does aerobic respiration occur?
In the mitochondria (mitochondrion singular)
When does anaerobic respiration occur?
When there is no oxygen available. An example of this is during exercise
Why do we aerobically respire rather than anaerobically? (2P)
Aerobic respiration produces more ATP molecules per glucose molecule than anaerobic, as in aerobic respiration the glucose molecule is fully broken down
The lactic acid produced can cause cramp
What is the equation for anaerobic respiration
glucose-> lactic acid
What is fermentation?
The product of anaerobic respiration in microorganisms and plant cells
What is the word equation for fermentation?
Glucose-> ethanol + carbon dioxide
What do plants need to make food and how do they get it? (2p)
Carbon Dioxide- Diffuses from the air into the plant through the stomata on the leaf
Water- Taken in through the soil by osmosis
What is the BALANCED word equation for photosynthesis
Carbon Dioxide + Water -> Glucose + Oxygen
6CO2 + 6H2O -> C6H12O6 + 602
Is photosynthesis endothermic or exothermic?
Endothermic
Give three examples for what glucose is used for (3p)
Makes cellulose, which is used to form cell walls
With added nitrogen, it makes proteins used for growth and repair
Makes fats and oils used as a food store and growth
How can you prove light, chlorophyll, and CO2 are essential for photosynthesis? Include safety issues
Step 1: Cut a leaf of a plant and place it in boiling water to kill it. This is so the stomata no longer work and therefore can’t take in CO2
Step 2: Place the leaf in boiling ethanol. This is done to remove all the chlorophyll, making sure it can not turn light into glucose
Step 3: Wash the leaf and spread it out on the white tile. This is to remove the ethanol
Step 4: Next, test for starch by adding iodine solution. We test for starch, as glucose is used to make starch in a plant. If starch is present, the leaf will turn blue-black. If this doesn’t happen, the experiment is a success
Safety Issues: Heat the ethanol in a water bath, as it is highly flammable
How can you prove light is needed for photosynthesis?
Step 1: Take a destarched plant and cover part of its leave with foil. We make sure it’s destarched, so that no starch is already present in the plant.
Step 2: Place the plant in sunlight for several hours
Step 4: Remove the foil and test the whole leaf for starch. You should find that in the covered area, no starch is present. Meaning no photsynthesis took place
What are the THREE limiting factors of photosynthesis?
Light intensity- The higher the light intensity, the faster the rate of photosynthesis. This increases until it hits the maximum rate
Carbon Dioxide- The greater the carbon dioxide concentration, the faster the rate. Farmers artificially increase this rate in greenhouses
Temperature- Photosynthesis is a series of enzyme-controlled reactions, meaning as temp increases, the rate increases until the enzymes are denatured
How do you work out relative light intensity using Elodea?
Relative light intensity=1/distance from light source^2
What is diffusion?
The net movement of particles from a high concentration to a low concentration, down a concentration gradient
Which factors affect the rate of diffusion?
The distance the particles have to travel across.
Increase the concentration gradient
Increase the surface area- Allowing more space for diffusion
What is osmosis?
The diffusion of water molecules across a semi-permeable membrane
What is turgid?
When a plant cell becomes stiff or rigid due to too much of water potential inside it
What is a plasmolyzed cell?
A plant cell that has too little of a water potential inside it
What is lysis?
When an animal cell bursts due to too much water potential inside it
What is active transport?
Active transport allows cells to move from an area of low concentration to an area of high concentration
What is needed for active transport to take place?
They need ATP, made in respiration
How are certain cells adapted for active transport?
Cells that use a lot of active transport contain a lot of mitochondria, meaning a lot of respiration takes place and a lot of ATP is made
What are carrier proteins?
Special proteins that span across the cell membrane that transport molecules in active transport
Give 2 examples of active transport
Digestion- Carbohydrates are broken down into glucose in the small intestine. The glucose is actively transported into the bloodstream, where it’s carried where it’s needed
Plants- Plants use active transport to take minerals in from the soil such as nitrate ions
How is DNA replicated? (5P)
- The DNA molecule unzips
- The DNA bases on each strand are exposed
- Free nucleotides in the nucleus line up against each strand, following the rule of complementary base
- This forms DNA base pairs
- When the whole strand is complete, their are two identical DNA molecules
What is mitosis?
The process by which body cells divide
What are three ways that sperm cells are differentiated?
Flagellum- whips from side to side to propel the cell to the ovum
Lots of mitochondria- This means a lot of respiration can occur, giving the cell a lot of energy
Acrosome- Stores digestive enzymes which break down the outer layers of the ovum
What are stem cells
Undifferentiated cells that divide by mitosis, and form cells that differentiate
What are the two main types of stem cells?
Embryonic stem cells- Found in embryos. They have the ability to differentiate (adapt) into all cell types
Adult stem cells- found in various body tissues and are able to differentiate into SOME different types of cell
What are meristems?
Parts of a plant that grow forever. Stem cells are found in meristems
Why is surface area: volume ratio important?
As the larger the surface area to volume ratio, the smaller the diffusion distance, and the smaller the organism
How are the alveoli adapted in order to increase the rate of diffusion?
They have thin alveolus walls
A large number of alveoli give a relatively large surface area
What is the circulatory system?
The system that carries oxygenated blood around the body
How does blood become oxygenated?
The heart pumps blood to the heart, where the oxygen diffuses into the blood cells through the alveoli
What is the structure of an artery and what is its job?
Thick outer wall
Thick layer of muscle
Small lumen
Carries blood away from the heart
What is the structure of a vein?
Fairly thin outer wall Thin layer of muscles Large lumen Have valves to stop blood flowing the wrong way Return blood to the heart
Why do humans have a double circulatory system?
As a double circulatory system ensures that blood is transported everywhere quickly, because humans are larger organisms
What are the 4 chambers in the heart?
The left upper atrium
The left lower ventricle
The right upper atrium
The right lower ventricle
How does deoxygenated blood travel?
The deoxygenated blood is brought into the right atrium by the vena cava
Then it flows into the right ventricle where it pumps it at high pressure through the pulmonary artery to the lungs
How does oxygenated blood travel?
The pulmonary vein brings oxygenated blood from the lungs into the left atrium
Then it flows into the left ventricle which pumps blood at high pressure through the aorta, where it is carried around the blood
What are the 4 things blood is made out of?
Red blood cells- They contain haemoglobin and carry oxygen
White blood cells- Large cells that fight disease by making antibodies
Plasma- Straw coloured liquid that blood cells float in
Platelets- Tiny structures that help the blood clot
What are the two transport systems in a plant?
The xylem and the phloem
What is the job of the xylem?
It transports water and mineral ions from the roots to the stem, leaves, and flowers. Water diffuses into the roots through diffusion. Mineral ions are actively transported into the root
What is the job of the phloem?
Transports dissolved sugars produced during photosynthesis, from the leaves to all other areas of the plant. This is called translocation
What is the structure of the xylem?
The xylem vessels are made from dead xylem cells. There aren’t any ends on these cells, forming tubes that the water and minerals can pass through. The rest of the xylem cell wall is thickened,
What is the structure of the phloem?
Phloem vessels are made of living cells. The cell walls of these cells do not completely break down. Instead, sieve plates are formed which allow the dissolved sugars to pass-through
What is transpiration?
The loss of water through a plant’s leaves
How is water lost from the leaves
Guard cells make the stomata open
Water evaporates from cells inside the leaf to the leaf’s air spaces
This creates a concentration gradient between the water vapour inside the leaf and the air outside it
Water vapour evaporates out
What is the cuticle
It is a waxy waterproof layer on the leaf that stops uncontrolled water loss
What causes a plant to wilt?
A plant wilts when it loses water faster than it gains it
What is a stimulus?
A change in the environment
What are sensory receptors?
Groups of cells that detect the stimulus
What are effectors?
Muscles or gland that respond from the stimulus
What does a sensory neuron do?
Carry electrical impulses from receptor cells to the CNS,
What does a relay neurone do?
Carry electrical impulses from sensory neurones to motor neurones, and are found in the spinal cord
What does a motor neurone do?
Carries electrical impulses from the spinal cord to the effector
What are reflex actions?
Actions that are automatic and that miss out the brain
What is the eye?
The sense organ that allows you to see
Where is the cornea found and what is its purpose?
Found on the front of the eye, protects the eye and refracts light entering the eye
Where is the pupil found and what is its purpose?
Central hole in the iris that allows light to enter the eye
Where is the iris found and what is its purpose?
ring of muscle tissue, alters the shape of the pupil
Where is the lens found and what is its purpose?
Found behind the iris, focuses light clearly onto the retina
Where is the ciliary muscle found and what is its purpose?
Found holding the suspensory ligaments in place, alters the shape of the lens
what is the suspensory ligaments purpose?
Connects the ciliary muscles to the lens
What is the optic nerve?
Nervous tissue, carries nerve impulses to the brain
How are images formed? (5 steps)
- The cornea refracts incoming light rays
- The light passes through the pupil
- The light is further refracted by the lens which creates a sharp image on the retina
- Photoreceptors in the retina produce a nervous impulse
- This impulse travels down the optic nerve to the brain
What happens to your lens when you want to see NEARBY objects?
Your ciliary muscle contracts, your lens becomes more convex (fatter).
What happens to your lens when you want to see DISTANT objects?
Your ciliary muscle relaxes, your lens becomes less convex (thinner).
What causes short sightedness?
Caused by the lens being too strong or the eyeball being too long
What causes long-sightedness?
Caused by the lens being too weak or the eyeball being too short
What types of lens can fix Long and short-sightedness?
SS-Concave lenses
LS-Convex lenses
What is colour-blindness?
A genetically inherited condition that means people can’t see certain colours
What is the function of the cerebrum?
Controls complex behaviour, like learning or memory
What is the function of the cerebellum?
Controls, posture, balance and involuntary movements
What is the function of the medulla?
Controls automatic actions such as heart rate
What is the function of the hypothalamus?
Regulates temperature and water balance
What is the function of the pituitary gland?
Stores and releases hormones
What are CT scans?
Computed Tomography scans that use X-rays to create 3D images of the inside of the body
What are MRI scans?
Magnetic Resonance Imaging Scans that use powerful magnets to identify brain abnormalities
What is the CNS?
Central Nervous System consists of your brain and spinal cord
What is the PNS?
Peripheral Nervous System consists of all the neurones that connect the CNS to the rest of the body
Why is damaging the PNS better than damaging the CNS?
The PNS can regenerate, but the CNS can only be fixed by surgery in limited situations
What are hormones?
Hormones are chemical messengers that cause a response in specific cells found in target organs
What are endocrine glands?
Glands that make hormones and secrete them into the blood
What is the endocrine system?
The name given to all the endocrine glands and the hormones they produce
What is thyroxine?
A hormone produced in the thyroid gland that plays a vital role in regulating the body’s metabolic rate
What is the function of the thyroid gland?
Takes iodine found in food and combines it with tyrosine to make thyroxine
What is negative feedback?
An important type of control that is used in homeostasis
What hormone stimulates the production of thyroxine in the thyroid gland
TSH- Thyroid-stimulating hormone
What is the menstrual cycle?
A monthly cycle in which a woman’s body get’s ready for pregnancy
What is the function of the uterus lining?
It protects the fertilised egg
What is the function of FSH?
Secreted by the pituitary gland and causes an egg to mature and stimulates the production of oestrogen
What is the function of Oestrogen?
Secreted by the ovaries, and causes the lining of the uterus to build up. As levels rise they inhibit the production of FSH and stimulate the release of LH
What is the function of LH?
Triggers ovulation, when the egg is released and if fertilised implants in the uterus lining
What is the function of progesterone?
Maintains the uterus lining and inhibits LH
What is a tropism?
When a plant detects a stimuli and grows in a specific direction as a response
What is auxin?
A plant hormones that cause plant cells in the shaded side of a plant elongate, causing it to bend towards the light
What does the plant hormone Ethene do?
Causes the plant fruits to ripen by stimulating the conversion of starch into sugar
What does the plant hormone Gibberellin do?
Promotes growth, particularly stem elongation
What happens when you get too hot?
Body hairs lower so they lie flat, preventing an insulating layer of air being trapped around the body
Sweat glands produce sweat, which evaporates off your skin
Blood vessels widen called vasodilation, increasing blood flow through the capillaries, increasing heat loss by radiation
What happens if blood sugar (glucose) levels are too high? 4 steps
- It is detected by the pancreas which releases the hormone insulin.
- Insulin then travels in the blood to the liver
- It stimulates the liver to turn glucose into glycogen
- Glycogen is stored in the liver, causing the blood sugar levels to fall
What happens if blood sugar (glucose) levels are too low? 2 steps
- The pancreas releases another hormone called glucagon
2. Glucagon makes the liver turn the glycogen into glucose, thus rising blood sugar levels
What is type 1 diabetes?
People who have Type 1 diabetes cannot produce insulin
It isn’t caused by lifestyle, and rather genetics
Can be controlled by regular insulin injection
What is type 2 diabetes?
People with type 2 diabetes cannot effectively use insulin
It is caused by lifestyle, e.g obesity
Controlled by a good diet and regulating carbs intake
What is urine?
A solution containing water, urea (a substance toxic to humans) and other waste substances
What happens if your short on water?
Your kidneys produce very little urine
How does blood travel through a nephron?
- Blood enters the kidney through the renal artery and into the glomerulus
- At the exit of the glomerulus, the blood vessels narrow, increasing the blood pressure
- This increased pressure forces small molecules out of the capillary into the bowman’s capsule. This is called ultrafiltration
- Next selective reabsorption takes place
- As the now filtered blood passes through the nephron, all of needed molecules are reabsorbed
- Finally the blood passes through the loop of Henle’, which regulate sat and water levels in the body by reabsorbing extra water and salt if needed
- The waste products that weren’t reabsorbed, from a solution, urine, which travels to the body
What happens in the kidney when water levels are low?
More ADH or Anti-diuretic hormone is secreted by the hypothalamus
ADH travels to the kidney where it causes the nephron tubes to be more permeable to water, meaning more water is absorbed in selective reabsorption and less water is lost
