B2 and B3 Flashcards
What is mitosis?
- A type of cell division
- It occurs when more cells are needed
- It produces two new cells that are completely identical to each other and the parent cell
- Mitosis is stage 2 of the process of growth and division called the cell cycle
where are chromosomes located the cells?
-In the nucleus
What is a chromosome?
-A DNA molecule that carries the genes that contain the instructions for making new cells
What is a gene?
- A small pocket of information that controls a characteristic, or part of a characteristic, of your body
- It is a section of DNA
- It has the genetic code for making a particular protein
How many chromosomes are in the nucleus of a body cell?
- 46 chromosomes
- Arranged in 23 pairs
- In each pair of chromosomes 1 pair is inherited from the father and 1 from the mother
What is DNA?
- a thread-like chain of nucleotides carrying the genetic instructions used in growth, development, functioning and reproduction
- DNA is contained in chromosomes
Describe what happens during the three stages of the cell cycle
Stage 1:
-cells grow bigger, increase in mass + carry out normal cell activities
-they replicate their DNA to form two copies of each chromosome ready for cell division
-they increase number of sub-cellular structures e.g. mitochondria, ribosomes and chloroplasts
Stage 2:
-mitosis: one set of chromosomes is pulled to each end of the dividing cell and the nucleus divides
Stage 3:
-the cytoplasm + cell membranes also divide to form two identical daughter cell
What is the cell cycle?
-A series of stages that the body cells divide into
Why is mitosis important in the body?
- It is essential for the growth, repair, and development of multicellular organism
- It keeps the organism alive
Where does mitosis take place in plants?
-Mitosis takes place throughout life in the meristems found in the shoot and root tips
Whats the difference between animal and plant cells in terms of differentiation?
- Many types of plant cells retain the ability to differentiate throughout life
- Most types of animal cells differentiate at an early stage of development and then don’t differentiate
What is differentiation?
- the process where a cell changes from one cell type to another
- usually changes to a more specialised type
What is a tissue?
-A group of cells with similar structure and function working together
What are organs?
- Collections of tissues performing specific functions
- Each organ contains several types of tissues
What forms organisms?
-Organs are organised into organ systems, which work together to form organisms
what are the functions of the liver in the digestive system?
-produces bile which helps the digestion of lipids
what are the functions of the small intestine in the digestive system?
-breakibg down large insoluble molecules into smaller soluble molecules and absorption
what are the functions of the stomach in the digestive system?
-breaking down large insoluble molecules into smaller soluble molecules
what are the functions of the large intestine in the digestive system?
-absorbing water from undigested food
What are the main organs used in the digestive system?
- liver
- stomach
- small intestine
- large intestine
What are carbohydrates made up of?
-units of sugar
What are simple sugars and how can you test for one?
- Carbohydrates that contain only one or two sugar units
- They turn blue benedict’s solution red when heated
What are complex carbohydrates and how can you test for one?
- They contain long chains of simple sugar units bonded together
- Examples of these are starch and cellulose
- Starch turns yellow-red iodine solution blue-black
What do lipids consist of and how can you test for one?
- Three molecules of fatty acids bonded to one molecule of glycerol
- The ethanol test indicates the presence of lipids in solutions
What chemical elements are carbohydrates made up of?
- Hydrogen
- Carbon
- Oxygen
What chemical elements are lipids made up of?
- Hydrogen
- Carbon
- Oxygen
What chemical elements are proteins made up of?
- Hydrogen
- Carbon
- Oxygen
- Nitrogen
What are proteins molecules made up of?
- Long chains of small units called amino acids
- There are 20 different amino acids
- Different arrangements of the various amino acids give you different proteins
What functions do proteins act as in the body?
- Structural components of tissues as muscles + tendons
- hormones e.g. insulin
- antibodies, which destroy pathogens
- enzymes, which act as catalysts
How can you test for proteins?
-Biuret reagent turns from blue to purple in the presence of proteins
What is a catalyst?
-substances that increases the rate of chemical reaction without changing chemically themselves
What is an enzyme?
- A substance which is a biological catalyst
- They catalyse specific reactions in living organisms due to the shape of their active site, this is the lock and key theory of enzyme action
What is the active site of an enzyme?
-The region of an enzyme where substrate molecules bind and undergo a chemical reaction
What are enzymes made up of and how does the lock and key theory work?
- They are made up of large protein molecules. the amino acid chains are folded to form the active site which matches the shape of a specific substrate molecule
- The substrate binds to the active site and the reaction is catalysed to the enzyme
What do enzymes control?
-The metabolism (the sum if all the reactions in a cell or in the body)
what types of metabolic reactions can different enzymes catalyse?
- building larger molecules from smaller ones e.g. starch from glucose
- changing one molecule into another e.g. glucose to frutose
- breaking down larger molecules into smaller molecules e.g. excess amino acids to form urea
How does temperature affect enzyme action?
- The rate of enzyme-controlled reactions increases as the temperature increases
- Highest part on graph is optimum temp which is around 40C, this is ideal temp for enzymes to work so reaction happen the fastest
- If temp goes above about 40C the protein structure of the enzyme is affected as the long amino acid chains will begin to unravel, changing the shape of the active site. the substrate will no longer fit in the active site so the enzyme has denatured
Why is it dangerous if your temperature gets too high when you are ill?
-your enzymes start to be denatured so none of the reaction in your body will occur fast enough which will result in death
How does pH affect enzyme action?
- a change in pH affects the forces that hold the folded chains of protein molecule in place
- so the shape of the active site is lost, and then the enzyme can no longer act as a catalyst
- however pH can also make it work very efficiently
Where do digestive enzymes work?
-Outside your body
What does digestion involve?
-the breakdown of large insoluble molecules into soluble substances that can be absorbed into the blood across the wall of the small intestine
How are digestive enzymes produced?
-By specialised cells in glands (salivary glands and your pancreas) and in the lining of your digestive system
Why do different areas of the digestive system have different pH levels?
- It allows the enzymes in that region to work as efficiently as possible
- E.g. the mouth and small intestine are slightly alkaline while the stomach has a low, acidic pH value
What does amylase catalyse the breakdown of?
-Of starch (carbohydrates) to simple sugars
What does protease catalyse the breakdown of?
-Of proteins to amino acids
What does lipase catalyse the breakdown of?
-Of lipids to fatty acids and glycerol
Where is amylase made in?
- Salivery glands
- Pancreas
- Small intestine
Where does amylase work in?
- Mouth
- Small intestine
Where is protease made in?
- Stomach
- Pancreas
- Small intestine
Where does protease work in?
- Stomach
- Small intestine
Where is lipase made in?
- Pancreas
- Small intestine
Where does lipase work in?
-Small intestine
What conditions do the protease enzyme pepsin from the stomach work best in?
- Acid conditions
- the stomach produces hydrochloric acid which maintains a low pH
What conditions do the enzymes made in the pancreas and the small intestines work best in?
-Alkaline conditions
How does bile make digestion efficient and where is it produced?
- Bile is produced by the liver, stored in the gall bladder, and released through the bile duct
- It neutralises acid that was added to the food in the stomach. so provides an alkaline condition for enzymes in the small intestine to work efficiently
