Biology B1 - B3 Flashcards
Where is genetic material found in Eukaryotic and Prokaryotic cells?
Eukaryotes - Nucleus
Prokaryotes - Cytoplasm
Formula for magnification
magnification = image size / real size
What are chromosomes?
Long molecules of coiled up DNA
Describe DNA’s structure
- Double Helix (Double stranded)
- Each of the two DNA strands is made up of lots of nucleotides joined together in a long chain.
What is the structure of a nucleotide?
Phosphate, Peniose sugar (ribose or deoxyribose) and a base
What are the four bases and their pairs?
Adenine, Cytosine, Guanine, Thymine
A-T
C-G
What is transcription in terms of protein synthesis?
Transcription is the process of copying DNA. This is done with the help of mRNA, or messenger RNA.
The DNA starts off by unzipping itself. This allows the mRNA to make a copy of the specific gene that is needed. The mRNA copies the complementary base pairs, but instead of A-T, it is A-U (Uracil). T-A still remains. For example, A-T-T-T-C-C is transcribed to be U-A-A-A-G-G
This mRNA is then sent to the ribosomes where it is then translated.
What is translation in terms of protein synthesis?
Translation takes the base pairs from the mRNA and splits them up into triplets, or codons. Each of these codons code for a specific Amino Acid.
tRNA, or translator RNA, goes back to the original strand of DNA and takes the second half of the unzipped strand, copying what’s on there and sending it back to the ribosomes. Amino acids are now formed here
What are enzymes?
Enzymes are biological catalysts that break that make chemical reactions within the body possible
What is the lock and key model?
Within an enzyme, there is an active site which has a shape specific to a certain substrate which it wants to break down. This substrate locks in and is broken down to form products
What are the effectors of enzymes
pH and Temperature
What is respiration?
The process of transferring energy from the breakdown of glucose. This energy is stored as ATP
What is Aerobic respiration?
Respiration when there’s plenty of oxygen
Glucose + oxygen –> carbon dioxide and water
What is Anaerobic Respiration?
Respiration without oxygen
In animals, lactic acid is produced (glucose –> lactic acid) whereas in plants, ethanol and carbon dioxide is produced (glucose –> ethanol + carbon dioxide)
Describe the steps of mitosis
Mitosis is cell division and here are the steps.
1) The cell has two copies of its DNA all spread out in long strings
2) Before the cell divides, the DNA forms X-Shaped chromosomes. Each “Arm” of a chromosome is an exact copy of the other.
3) The chromosomes then line up at the centre of the cell and the cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cells.
4) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.
5) The cytoplams divides and you are left with two daughter cells.
What is cell differentiation?
Differentiation is the process by which a cell changes to become specialised for its job. In most animal cells, the ability to differentiate is lost at an early stage, but lots of plant cells dont ever lose this ability.
What are stem cells?
Stem cells are undifferentiated. Depending on what instructions they’re given, they can divide by mitosis to become new cells.
Embryonic stem cells
Embryonic stem cells are found in early human embryos. They have potential to turn into any kind of cell at all. However, there is a lot of ethics behind not being able to use them
Adult stem cells
Adult stem cells are only found in places such as bone marrow, but they aren’t as versatile as embryonic stem cells. They can only turn into cells from the tissues they originally came from.
Diffusion, Active transport and Osmosis
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. They go down a concentration gradient
Osmosis is the net movement of water molecules from a region of high water potential to low water potential across a partially permeable membrane. They go down a concentration gradient.
Active transport is diffusion, but going against a concentration gradient
Transpiration
Transpiration is the movement of food and water through a plant cell.
In phloem tubes, food is transported both up and down the stem to growing and storage tissues. This movement of food substances is known as translocation.
Xylem tubes take water up the plant.
They’re made of dead skin cells and thick side walls made of cellulose to support the plant. They carry water and minerals from the roots up the shoot to the leaves in the transpiration stream.
Transpiration is the loss of water from the plant. Due to the stomata opening and closing, the water that travels up can evaporate and diffuse out the cell.
What effects transpiration?
Light intensity
Temperature
Air movement
Describe how information is transmitted in the nervous system
Stimulus - receptor - sensory neurones - CNS - motor neurones - effector - response
The body has lots of sensory receptors, which can detect a change in your environment.
The receptors then sends these nervous impulses along sensory neurones to the CNS
The CNS consists of the brain and spinal cord.
The CNS coordinates the response
This information is then sent to the effector along the motor neurone and this effector then responds accordinglu
How does the structure of neurones allow transmitting of electrical impulses?
Electrical impulses are passed along the axon of a neurone.
Neurones have branched endings (dendrites) so they can connect with lots of other neurones.
Some axons are also surrounded by a fatty (myelin) sheath. This acts as an electrical insulator, speeding up the electrical impulse.
Neurones are long, which also speeds up the impulse (one longer neurone is faster than 5 short ones)
The connection between two neurones is called a synapse, or just a tiny gap:
- The electrical impulse triggers the release of transmitter chemicals, which diffuse across the gap
- These chemicals bind to receptor molecules in the membrane of the next neurone, setting off a new electrical impulse
