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what is a gamete?
sex cell (egg or sperm)
what is the genome?
all the DNA in one cell of an organism/ a the genes present
what is a chromosome?
a long continuous thread of DNA that consists of numerous genes, tightly packed
how many chromosomes do human body cells have?
46 (23 pairs)
how many chromosomes do human gametes have?
23 chromosomes
where are chromosomes located?
nucleus of a cell
what is a gene?
segment of DNA that codes for a protein
describe the structure of DNA
- polymer made of many nucleotide monomers
- double stranded helix
name the 4 bases of DNA
Adenine, Thymine, Cytosine, Guanine
what are the differences between DNA and RNA?
DNA: double stranded, has deoxyribose sugar, bases: A, T, G, C
RNA: single stranded, has ribose sugar, bases: A, U, G, C
how do the bases of DNA pair up?
Adenine pairs with Thymine
Guanine pairs with Cytosine
describe transcription
-copying part of the nucleotide sequence of DNA into a complementary sequence in RNA
- DNA unzips
- complementary mRNA nucleotides bind
- mRNA leaves nucleus
what is a codon?
group of 3 mRNA bases that code for single amino acid
what is an anticodon?
3 bases on tRNA molecule that is complementary to mRNA
describe translation
- mRNA travels to a ribosome
- tRNA molecules with an anticodon that matches the codon on the mRNA molecule carry amino acids to the ribosome
- the amino acids are joined together
how does the sequence of bases affect the protein made in photosynthesis?
DNA is a triplet code where 3 bases code for one amino acid and the order of amino acids determine the protein produced
what is an allele?
different forms of the same gene
what is a dominant allele?
only one (out of the two alleles) is needed for it to be expressed and for that (corresponding) phenotype to be observed/ displayed
what is a recessive allele?
two copies of the allele is needed for it to be expressed
what is meant when an organism is homozygous?
when an organism has two copies of the same allele (two recessive or two dominant)
what is meant when an organism is heterozygous?
when an organism has two different versions of the same gene (one dominant and one recessive)
what is the genotype?
genetic makeup of an organism
what is the phenotype?
physical characteristics of an organism
what is codominance?
when both alleles contribute to the phenotype
what is monohybrid inheritance?
the inheritance of a single gene/ allele
what do family perigees show?
the inheritance of an allele over generations
give 3 processes that require mitosis
growth, repair, asexual reproduction
how many cells does mitosis produce?
2 daughter cells
how many chromosomes in each daughter cell in mitosis?
46 in human, diploid
how many cells does meiosis produce?
4 daughter cells
how many chromosomes in each daughter cell in meiosis?
23 in humans, haploid
give 5 differences between mitosis and meiosis
Meiosis:
1. homologous chromosomes are in pairs
2. crossing over
3. 2 nuclear divisions
4. 4 cells produced
5. daughter cells are genetically different from each other
what is random fertilisation?
- the random chance of a specific sperm combining with a specific egg
- this increases variation as any female can mate with any male and any one of the millions of sperm could fertilise the egg
what are the two types of variation?
genetic and environmental
state 2 traits in humans caused only by genetic variation
eye colour, blood type
state 2 traits in humans caused by a mix of environmental and genetic variation
height and weight
what is a mutation?
random change in genetic material that can be inherited
how do mutations alter the phenotype?
- mutations alter the genetic material (DNA)
- this can cause it to code for a different sequence
of amino acids
- a different sequence of amino acids means that
the protein will be different
give 3 environmental factors that can increase the chance of mutations
- exposure to ionising radiation
- exposure to X-rays, gamma rays, UV
- certain chemicals, particularly those found in cigarette smoke
describe the process of natural selection
- populations are naturally varied due to random genetic mutations
- some of these mutations provide a selective advantage
- these organisms survive and reproduce, passing on the successful genes
define evolution
the change in the genetic makeup of a population over time due to natural selection
describe how antibiotic resistance arises
- a random genetic mutation causes a bacterium to become resistant to the antibiotic
- when the antibiotic is used, all the bacteria that do not have the mutation are killed
- whe population containing just the resistant bacteria then begins to grow
what are the risks of antibiotic resistance?
Resistant bacteria survive in the presence of the antibiotic and continue to multiply causing longer illness or even death
Name organelles in animal cell
Cell membrane, cytoplasm, mitochondria, nucleus
What is an enzyme?
Biological catalyst which speeds up a reaction without being used up itself
What is anaerobic respiration?
respiration without oxygen
Define diffusion
Movement of molecules from a high to low concentration
What can speed up the rate of diffusion?
Larger concentration gradient
Higher temperature
Decreased distance
Surface area increased
Describe the term 'active transport'
Movement of molecules from low to high concentration
Using energy (ATP)
Describe the term 'osmosis'
Diffusion of water molecules
from high water potential to a low water potential
through a partially permeable membrane.
Name some specialised cells?
1. Nerve cell (neurone)
2. Villi cell
3. Xylem vessel from the plant stem
4. Guard cells from surface of a leaf
5. Leaf palisade cell
6. Sperm cell / egg cell
7. Cilia cell
8. Red blood cell
What is a tissue?
Cells grouped together which have a similar function
What is the endocrine system?
Include glands which secrete hormones that act as chemical messengers
What are the 7 key elements of a balanced diet?
Carbohydrates, lipids, protein, mineral, vitamins, water and fibre
What is the importance of carbohydrates?
Respiration and short term store of energy
Where is lactose found?
In milk
Where is sucrose found?
Plants
What is starch?
Starch is a complex carbohydrate which is an insoluble molecule.
What is glycogen?
Complex carbohydrate in animals (long term store)
What is cellulose?
Complex carbohydrate in plants (long term store) - plant cell walls made of it
What are the three elements that make up lipids?
Hydrogen, carbon and oxygen
What are lipids made of?
Glycerol joined to three fatty acids.
What is the role of fat in the body?
Insulation, energy store, protection,
Why do we need protein?
Growth and repair of tissues. Many compounds in the body are made from protein, including enzymes, hormones, antibodies
What do proteins consist of?
Many amino acids
What are the four chemical elements all amino acids contain?
Carbon, hydrogen, oxygen and nitrogen.
What is Calcium used for and what is its role in the body?
Making teeth and bones and is found in dairy products, fish, bread and vegetables.
What is Phosphorus used for and what is its role in the body?
Making teeth and bones; part of many chemicals e.g. DNA
How do you test for starch?
Add a drop of iodine solution to the subject. If starch is present it will turn a 'blue-black' colour.
How do you test for glucose?
Benedict's solution - Heat (85C) - Blue to red brick
Name two types of mechanical digestion and how they work...
In the mouth where the teeth bite and chew the food cutting it into smaller pieces that have a larger surface area.
Muscles in the wall of the stomach contract to churn up the food whilst it is being chemically digested.
What is the process of movement of food in the gut called?
Peristalsis
Name all the organs in the digestive system from the mouth to anus...
Mouth, salivary gland and tongue, oesophagus (gullet), liver, gall bladder, stomach, pancreas, small intestine (duodenum and ileum) , large intestine ( colon and rectum), appendix and anus.
What enzyme digests lipids?
Lipase
Where is pepsin produced?
stomach wall
What enzyme digests proteins?
Pepsin
What breaks down lipids? And into what?
Lipase: Lipids --> Glycerol and fatty acids
The stomach wall secretes hydrochloric acid, why is this important?
As it kills the bacteria that are taken into the gut along with food. Also Pepsin, has a optimum pH value of about 2.
What is the purpose of bile?
Fat droplets broken into smaller droplets to increase surface area (for lipase to work on)
It also neutralises stomach acid because it's alkaline
What is the purpose of the ileum?
It is the part of the small intestine where the soluble products of digestion get absorbed into the blood.
What is peristalsis?
Wave-like muscle contractions that moves food in the digestive tract
Name three ways in which the ileum is tailored for quick and efficient absorption of products?
It is very long which provides a large surface area.
Has folds in its lining- increase surface area.
It has tiny projections from the lining called villi which also project microvilli- increases surface area. It also has a lacteal to absorb fats.
What is the job of the large intestine?
Water absorption.
What is ingestion?
Taking in of substances such as food into the mouth
What is digestion?
Mechanical and chemical- breaking down and absorption of substances
What is egestion?
Getting rid of undigested and unabsorbed 'food' from the gut, in humans it is called faeces from the anus.
What is excretion?
Removal of metabolic waste (e.g. co2, urea)
What is the role of ADH?
Controls the water content of the blood by making collecting duct more permeable
What is homeostasis?
Keeping a constant internal environment
Name 4 ways in which water can be lost?
Exhaled air, sweat, urine, faeces
Name 3 ways in which water can be gained?
Food, water, cells respiration
What is the role of the bowman's capsule in the nephron?
collects the glomerulur filtrate and helps the glomerulus filter blood
How does ADH affect the amount of water being reabsorbed?
More ADH makes collecting duct more permeable
More water reabsorbed into bloodstream
Urine more concentrated
Less urine produced
What does urine contain?
Water, Urea and salts
State how you would test for starch and the colours you would see.
Add iodine and when starch isn't present it will be yellow brown, if it is present it will go blue-black
What is a tropism?
The growth response to a directional stimuli
What is phototropism?
A growth response to light
What is geotropism?
A growth response to gravity
What is auxin?
A plant growth hormone found in the tip of plants
What is a producer?
Plants which photosynthesise to produce food
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