B3 Flashcards
What 6 cell structures are found in a plant cell?
Nucleus Cytoplasm Chloroplasts Cell wall Vacuole Cell membrane
What 4 cell structures are found in bacterial cells?
Cell membrane
Cytoplasm
Cell wall
Single circular strand of DNA
What does nucleus contain?
The DNA in the form of chromosomes
What does the cell membrane do?
Holds the cell together and controls what goes in and out
What happens in the ribosomes?
Proteins are synthesised
What’s cytoplasm?
A gel like substance where most of the cells chemical reactions happen
What happens in mitochondria?
Respiration - provides energy for cell processes
Many found in liver cells (carry out energy demanding metabolic reactions)
and muscle cells (need energy to contract)
What is the cell wall?
Made of cellulose and supports the cell shape
Where does photosynthesis happen in the cell?
In the chloroplasts
What is the vacuole?
Relatively large structure such as containing sap (a weak solution of sugar and salts)
What is the structure of DNA?
Double helix
Each strand is made up of small groups of nucleotides
Each nucleotide contains a small molecule called a base
Each base forms cross links to an opposite base holding the strands tightly wound together
What are the four different bases and what are their pairing?
A C T G
A-T
C-G
Complementary base pairing
What did Watson and crick discover?
First to build a model of DNA a 1953
DNA structure
What are the stages of DNA replication?
Double helix unzips to form two strands
New free floating nucleotides join on using complementary base pairing making an exact copy on each strand
What controls the production of proteins in a cell?
DNA
The section that codes for a particular protein is a gene
What are proteins made up of?
Chains of amino acids
What’s different about different proteins?
Each has a specific number and order of amino acids giving each a different shape to do different functions
How does a gene code for protein?
Order of the bases in a gene decides the order of amino acids in protein
Each amino acid is coded for by three bases
How are proteins made?
mRNA carries the DNA code to the ribosomes (by copying it from the DNA) to make proteins
How does DNA control a cell?
Decides what kind and how many proteins are made
Some genes are switched off
E.g in muscle cell only muscle cell proteins are switched on
What are the four kinds of proteins?
Enzymes
Carrier molecules
Hormones
Structural proteins
What 5 cell structures are found in an animal cell?
Nucleus Cell membrane Ribosome Cytoplasm Mitochondria
What do carrier molecules do?
Transport smaller molecules e.g haemoglobin binds to oxygen molecules and transports them around the body
What do hormones do?
Carry messages around the body
What are structural proteins?
Physically strong
E.g. Collagen strengthens connective tissues
What do enzymes do?
Control cell reactions
What usually makes a reaction happen faster?
By raising the temperature
What are enzymes and why does our body produce them?
Biological catalysts
Speeds up the reaction without hearing it up which damaged the cells
What’s special about different enzymes?
Every different biological reaction has its own enzyme specifically designed for it
Every enzyme is codes for by a different gene
Each has a unique shape
What is a substrate?
The molecule changed in a reaction
What is an active site on an enzyme?
The part where it joins on to the substrate to catalyse the reaction
What’s special about enzymes?
They have a high specificity for their substrate (only work for one substrate)
Why are enzymes so specific?
The substrate has to match the shape of the enzymes active site if it doesn’t fit it won’t be catalysed
“Lock and key” mechanism
Why does a higher temperature increase the rate of reaction?
More heat = more energy for the enzymes and substrate to move about and collide with each other - higher collision rate
What happens to enzymes if a reaction is too hot?
Some of the bonds holding the enzyme together will break so it will lose its shape - active site won’t fit substrate - can’t function
It is denatured
What does an enzymes optimum temperature mean and what is the right temperature for human enzymes?
It’s the temperature that the reaction goes the fastest at
37 degrees C
What happens to enzymes if the pH is too high or low?
Interferes with bonds , enzyme loses shape - denatured
All enzymes have an optimum pH
What’s a Q10 value?
Shows how much the rate changes when the temperature is raised by 10 degrees
How do you calculate the Q10 value?
Rate at higher temperature
——————————–
Rate at lower temperature
What does it mean if the Q10 value is 2?
The rate doubles
If it’s three it trebles ectr….
What is a gene mutation and what can it cause?
Change in the DNA base sequence
It could stop the production of the protein the gene normally codes for - or a different protein could be produced instead
How can mutations be harmful?
Producing the wrong protein or none at all can be disastrous - especially if the protein is an important enzyme
If it occurs in reproductive cells the offspring might develop abnormally or die
If it occurs in body cells they could multiply uncontrollably and invade other parts of the body - cancer
How can mutations be beneficial?
The different protein produced could be an improvement on the old one
Gives them a survival advantage , gets passed on to next generation and becomes common - natural selection
What two things increase the chance of mutations occurring?
Ionising radiation (UV light and X-Rays and from radioactive sources) - greater the dose the greater the chance of mutation Certain chemicals called mutagens (if the mutagens produce cancer they are called carcinogens)
What are 3 advantages of being multicellular?
You can be bigger - therefore can travel further, get nutrients in variety of ways, less things can eat or kill you
Cell differentiation - cells can be specifically adapted for their job
More complex - specialised organs, different shapes and behaviour a specific adaptations to your environment
What are the disadvantages to being multicellular?
Need specialised organ systems e.g.
Nervous system - cell communication
Circulatory system- supply nutrients
Respiratory system- exchange substances with environment
What is mitosis?
It’s when a cell reproduces itself by splitting to produce two identical offspring
When is mitosis used in the body?
For growth
Replace worn out cells
Repair tissues
What are the 5 stages of mitosis?
DNA in cell is replicated
DNA coils into double armed chromosomes
Chromosomes line up in middle of cell then divide as cell fibres pull them apart - arms split and get pulled to opposite poles of the cell
Membranes form around each one armed cluster
Cytoplasm divides creating two new cells genetically identical
What’s different about the arms in a double armed chromosome?
NOTHING!!! Lol trick question!!
The left arm has exactly the same DNA as the right arm
What does diploid mean and give an example of a diploid cell
Each cell has two copies of each chromosome in its nucleus
Body cells
What does haploid mean and give an example of a haploid cell
Cells only have one copy of each chromosome
Gametes
What’s the main difference between meiosis and mitosis?
Meiosis has two divisions whereas mitosis only has one
Mitosis produces genetically identical cells