BIOLOGY FLASHCARDS FOR TOP MARKS ABOUT EVERYTHING

What is an example of a free living nitrogen-fixing bacteria?

Azotobacter

What is an example of a mutualistic nitrogen-fixing bacteria?

Rhizobium

What is an example of nitrifying bacteria that converts ammonium ions to nitrite?

Nitrosomonas

What is an example of a nitrifying bacteria that converts nitrite to nitrate?

Nitrobacter

What is selection pressure?

Selection pressure is an external factor in an environment that influences an organism's reproductive success, favoring individuals with certain traits while disadvantaging others

What is the equation to caculate cell divison?

N=N₀*2ⁿ Where N is original number of cells and n is number of cell divisions that have occurred.

What is selection pressure?

A selection pressure is an environmental factor that influences an organism's ability to survive and reproduce, driving natural selection

What moves deoxygenated blood from the heart to the lungs? 

Pulmonary artery 

What brings oxygenated blood from the heart to the lungs?

Pulmonary vein

Where do arteries take blood and where do veins take blood?

Veins take blood towards the heart and arteries take blood away from the heart.

Where does the aorta take blood?

Oxygenated blood from the left ventricle in the heart to the rest of the body.

Where does the vena cava take blood?

Deoxygenated blood from the rest of the body towards the right atrium in the heart.

Where does renal vein carry blood to?

Deoxygenated blood towards the right atrium in the heart from the kidneys.

Where does renal artery carry blood to?

Oxygenated blood from the left ventricle towards the kidneys.

What is partial pressure?

The partial pressure of oxygen is a measure of oxygen concentration. Partial pressure is measured in kilopascal (kPa). The greater the concentration of dissolved oxygen in a cell, the greater the partial pressure. Haemoglobin has different affinities for oxygen depending on its partial pressure.

What is this called and what is its function?

The golgi body and it processes, packages and modifies proteins and lipids to be transported to their final destination in or outside of the cell.

What is this red organelle called and what is its function? 

The rough endoplasmic reticulum and it is embedded with ribosomes to allow it to carry out protein synthesis such as modification and folding. While specifically it receives new proteins synthesized by its attached ribosomes, further folds them into their correct 3D shapes, and modifies them by adding carbohydrates (glycosylation) to create glycoproteins. 

What elements are present in triglycerides, cellulose and antibodies? 

Triglycerides/ C,H,O

Cellulose/ C,H,O

Antibodies/ C,H,O,N,S

How to test for lipids in a sample?

• Firstly add ethanol to a sample and shake well.

• Then add in equal parts water and a positive result will have a white milky emulsion form.

How to test for reducing sugars?

• Add benedict’s reagent, heat in a water bath for 80 degrees celsius for 5 minutes.

• A positive result is indicated by the solution turning brick red (can be blue,green,yellow or orange depending on concentration).

How to test for non-reducing sugars?

• Add benedict’s reagent and heat in a water bath at 80 degrees celsius for 5 minutes. If result remains blue continue to next steps. 

• Add dilute hydrochloric acid (HCI) and heat to hydrolyse glycosidic bonds. 

• Neutralise with sodium hydrogen carbonate which is alkaline. 

• Repeat the Benedict’s test and a positive result will show a change in colour from blue to brick red. 

How to test for starch? 

• Add iodine solution to the sample

• A positive result is indicated by a change in colour from orange-brown to black

How to test for proteins? 

• Add biuret reagent which contains sodium hydroxide and copper sulphate to sample.

• Positive result indicating by change in colour from light blue to purple.

Describe the processes involved with transcription? 

• Firstly, RNA polymerase breaks the hydrogen bonds between complementary base pairs separating the DNA strands and exposing the bases.

• Next, RNA polymerase adds RNA nucleotides to complementary bases on one strand of DNA called the template strand. 

• After the nucleotides are added by RNA polymerase, the DNA helix behind is reattached. 

• RNA polymerase continues along the strand forming phosphodiester bonds between adjacent nucleotides until the pre-mRNA is completed

• The pre-mRNA strand and RNA polymerase detach, leaving behind the original DNA helix and a complete strand of mRNA. 

What is the speed of an action potential travelling down the axon called?

The speed of conductance

What are the two main purposes of the refractory period?

• To ensure that action potentials are unidirectional and only travel away from the receptor.

• To ensure action potentials are discrete and separate as they travel along the axon of neurons.

How sensitive are rod and cone cells to light?

Rod cells are very sensitive to light and cone cells and cone cells are less sensitive to light, requiring bright light.

What type of vision do cone and rod cells provide?

Rod cells provide black and white vision and cone cells provide colour vision (red,green,blue cones)

How does visual acuity differ between rod cells and cone cells?

Visual acuity is lower in rod cells providing poor detail, whilst con cells have high acuity providing fine detail.

What is visual acuity?

Visual acuity is a measure of how clearly and sharply you can see details

How are rod cells and cone cells distributed in the eye?

Rod cells are mainly found in the peripheral retina ; absent from the fovea. Meanwhile cone cells are highly concentrated in the fovea; fewer in the peripheral retina.

What photopigments are in rod and cone cells?

Rod cells have rhodopsin and cone cells have iodopsins (three types, each sensitive to different wavelengths)

How many neural connections do rod and cone cells have?

Rod cells have high convergence- many rods connect to one bipolar neuron. Meanwhile cone cells have low convergence- often one cone to one bipolar neuron.

Number of cone and rod cells in the retina?

There are 120 million rod cells in the human retina and about 6 million conce cells.

What does the eye’s structure consist of?

The eye's structure involves three layers: the outer fibrous (sclera, cornea), middle vascular (choroid, ciliary body, iris), and inner neural (retina with rods/cones, optic nerve) layers

Label these features

Define resting potential and threshold potential

• Resting potential: Membrane potential at rest (~–70 mV).

• Threshold potential: The critical level (~–55 mV) the membrane must reach for an action potential to occur.

Define depolarization

• The neuron membrane becomes less negative than the resting potential (towards 0 mV).

• Voltage-gated Na⁺ channels open and Na⁺ ions diffuse into the cell down a concentration gradient.

• Associated with the rising phase of an action potential.

Define repolarization

• The membrane potential returns toward the resting potential after depolarisation.

• Caused by K⁺ ions diffusing out of the cell through voltage-gated K⁺ channels.

• Associated with the falling phase of an action potential.

Define hyperpolarization

• The membrane potential becomes more negative than the resting potential.

• Happens when K⁺ channels remain open too long or Cl⁻ enters.

• Occurs during the after-hyperpolarization phase, contributing to the refractory period.

Describe the process of a synapse

• Firstly an action potential arrives at the presynaptic neuron and causes the voltage gated calcium

What enzyme breaks down acetylcholine?

Acetylcholinesterase

Which part of the brain is the cardiovascular centre located?

The medulla oblongata.

What neuron connects the brain to the adrenal gland?

The neuron that connects the brain (via the spinal cord) to the adrenal gland is a preganglionic sympathetic neuron

What does stimulating the preganglionic sympathetic neuron do?

Leads to rapid and mass secretion of hormones triggering the fight or flight response

What neuron connects cardiovascular center of brain to sinoatrial node?

The neurons that connect the cardiovascular center in the brain (medulla oblongata) to the sinoatrial (SA) node are the parasympathetic neurons (via the vagus nerve) and sympathetic neurons (via the cardiac accelerator nerves). 

Effects of stimulating the parasympathetic neurons (via the vagus nerve) and sympathetic neurons (via the cardiac accelerator nerves).

Stimulating the vagus nerve decreases the heart rate (bradycardia). Acetylcholine binds to muscarinic receptors on the SAN, making the membrane potential more negative (hyperpolarizing it) and reducing the frequency of electrical impulses generated by the SAN, thus slowing the heart rhythm. 

Describe how an impulse reaches the base of the ventricles of the heart from the sinoatrial node.

It spreads through the atria / right atrium / through cardiac muscle;

to the atrioventricular node;

then through conduction fibres / bundle of His

What gradient do sodium ions move down to enter post synaptic neuron?

Electrochemical gradient

How many receptor sites does each sodium channel have?

Three receptor sites for neurotransmitters which cause them to open

What is the sequence of events called occuring between the pre and post synaptic neuron?

Synaptic transmission

What do mitochodnria do in the pre-synaptic neuron?

Enable the movement of acetylcholine into synaptic vesicles which fuse with the membrane and release the neurotransmitter into the synaptic cleft.

What enzyme breaks down acetylcholine?

Acetylcholinesterase

What reaction does acetylcholinesterase uses to break down acetylcholine?

Hydrolysis

Why is hydrolysing acetylcholine important?

It allows for discrete action potentials to occur which are seperate.

How do choline, ethanoic acid enter the cell and how does acetylcholine enter the vesicle?

• Choline enters the cell via facilitated diffusion as it is charged.

• Ethanoic acid enter the cell via simple diffusion as it is not charged.

• Acetylcholine enters the vesicle carrying it by active transport

What does the synaptic knob have a lot of?

Mitochondria so ATP can be provided to the cells allowing active transport of acetylcholine into vesicles to occur quickly and reduce time between synaptic transmissions.

How is acetylcholine formed?

Ethanoic acid and choline are combined by an enzyme to form the neurotransmitter.