Biology Flashcards
Function of the cell membrane
Protection and a fixed environment
Function of the cytoplasm
Site of chemical reactions
Functions of nucleus
Carries genetic information, cell controller
Function of mitochondrea
Site of respiration
Function of cell wall
(Only in plants)
Structure and support
Function of chloroplast
(Only in plants)
Capture energy for photosynthesis
Function of vacuole
(Only in plants)
Fluid filled membrane, storage function
Function of chromosomal DNA
(In prokaryotic cells)
Carry genetic information
Function of Plasmid DNA
(In prokaryotic cells)
Carry genetic advantages
Organisation of structures
Cells - tissues - organ - organ system
Definition of diffusion
Diffusion is the passive net movement of anything from a region of higher concentration to a region of lower concentration.
eg: Perfume in a room, gas exchange
Definition of osmosis
Net movement of water along a semi-permeable membrane.
eg: Soil absorption, salt in potatoes
Definition of active transport
Movement of a substance against a concentration gradient using a carrier protein.
eg: Glucose intake in intestines, root hair cell
What is mitosis
Interphase, followed by PMATC (mitosis) to produce genetically identical daughter cells
Mitosis plays a role in…
Repair, growth and asexual reproduction
Cancer is the result of…
Changes in cells that lead to uncontrolled cell growth and division (mutations)
What is meiosis
Interphase followed by two consecutive divisions to produce a haploid nucleus - 4 genetically different daughter cells
Meiosis and chromosome number
Initially reduces chromosome number which is later restored at fertilisation
Asexual reproduction results in…
Identical offspring, given no mutations, from one parent
Sexual reproduction results in…
Genetically different offspring, resulting from 2 parents and 2 haploid nuclei
Female chromosomes
XX
Male chromosomes
XY
Gene definition
Unit of hereditary, part of a chromosome
Allele definition
Alternative form of a gene
Dominant definition
Always expressed
Recessive definition
Expressed in the absence of a dominant gene
Heterozygous definition
Different alleles
Homozygous definition
Same alleles
Phenotype definition
Observable characteristics from the genotype
Genotype definition
Genetic constitution of an individual
Chromosomes
Made up of proteins and DNA organized into genes. Each cell normally contains 23 pairs of chromosomes
Inherited conditions are typically…
Recessive, inherited from 2 carrier parents
Phenotype features are the result of…
Multiple gene inheritance rather than single genes
What is the genome
The entire genetic material of an organism
DNA structure
Polymer, made up of 2 strands forming a double helix
Contents of nucleotide
Common sugar, phosphate group and a base
What are the 4 bases
Adenine(L), Thymine (2 bonds), Cytosine and Guanine(L) (3 bonds)
Protein synthesis overview
Genes carry the code for proteins, the code is read in triplets (each triplet coding for one amino acid) which are then ordered and folded to form a protein
Gene mutations
Change in the DNA, and don’t always affect the phenotype because DNA is degenerate
Genetic engineering overview
- Taking a copy of a gene from DNA/ chromosomes of 1 organism
- Insertion of that gene into the DNA of another organism
- Involves restriction enzymes (cutting) and ligases (sticking) as well as a vector for transport
Embryonic stem cells…
Can give rise to ANY cell type, but cells loose the ability to differentiate as the animal matures
Stem cell function
Provide new cells for growth or replace damaged cells
Adult stem cell function
Regenerate damaged tissues, but specifically to a specialised tissue
Variation within a population is usually…
Genetically extensive
Evolution definition
Change in the inherited characteristics of a population over time through a process of natural selection and a change in allele frequency that MAY result in the formation of a new species
Types of variation
Genetic/ inherited or it can be environmental (affecting the phenotype)
Enzymes are…
Biological catalysts
Enzyme mechanism
Lock and key, enzyme substrate theory - Specific active site with a binding site on the substrate
Temperature on enzymes
Increase the reaction rate to the optimum, beyond which the enzymes will denature and the reaction rate will drop dramatically
pH on enzymes
Increase the reaction rate to an optimum, beyond which the enzymes will denature and the reaction rate will drop dramatically
Amylase is produced and found in the…
Salivary glands and the pancreas
Proteases are produced and found…
Stomach, pancreas and small intestine
Lipases are produced and found…
Pancreas, mouth and stomach
Function of amylase
Breaks bonds in starches/ polysaccharides into simple sugars
Function of protease
Digests protein into amino acids
Function of lipase
Breaks down fats into fatty acids and glycerol
Cellular respiration
Exchange of CO2 for O2
Aerobic respiration equation
C6H12O6 + O2 -> CO2 + H2O. Mostly occurring in mitochondria, in wealth of O2
Anaerobic respiration
Converts glucose into lactic acid and energy.
C6H12O6 -> 2C3H603 + 2ATP. No wealth of O2 means small quantities of energy.
CNS is comprised of
Brain and spinal cord
Sensory neurones
Receptor - axon - body - dendron. Sends electrical impulses to a relay neuron which is located in the spinal cord
Relay neurones
Dendrite - body - Axon. Connect sensory neurones to motor neurones
Motor neurones
Dendrite - body - axon. Connects to an effector
Synapse function
1st dendrite receives an electrical impulse at end of axon, neurotransmitters are released, chemicals diffuse across the synapse, binds to the receptor molecules on the 2nd neuron membrane and stimulates second impulse
Reflex arc
Spontaneous, quick reaction, no conscious brain involvement. Stimulus - Receptor - Sensory neurone - Relay - Motor - Effector - Response
How do the lungs work?
Low pressure inside the intercostal space pulls air inwards as the diaphragm contracts, moves downwards and the intercostal muscles contract
High surface area: Volume ratio =
Efficient gas exchange
Circulatory system order, starting from the Left Atrium
LA - LV - A - BODY - VC - RA - RV - PA - PV - LA
Composition of the blood
RBCs (O2), WBCs (Antibody production + phagocytosis), Platelets (Blood clotting) and Plasma (transport of blood components and dissolved substances like CO2, urea and heat)
Order of digestive system
Oesophagus, stomach, gallbladder, small intestine, large intestine, rectum and anus. Pancreas secretes digestive enzymes on the way.
Function of oesophagus
Muscular tube to the stomach
Function of stomach
Digestion
Function of gallbladder
Stores liver bile
Function of small intestine
Mixes food with enzymes and bile
Function of large intestine
Reabsorption of water
Function of rectum
Stores faeces
Function of anus
Excretes faeces
Peristalsis
Muscle contractions to move food along, begins in the oesophagus when a food bolus is swallowed
Digestion
Turns food into nutrients and energy for growth and cell repair
Absorption
Movement of nutrients, water and electrolytes from the lumen of the small intestine into the cell and blood
Egestion
Discharge of undigested food as faeces
Kidney purpose
Regulate water content and remove toxic waste
Kidney function in the nephron
Unafiltration in the Bowman’s capsule of salts, glucose (high pressure), the selective reabsorption of glucose, salts and lots of water at the loop of Henle before final reabsorption of more/ less water.
What is homeostasis?
Maintenance of a constant internal environment
Negative feedback
Output function tends to reduce fluctuation if other output
Function of insulin
Encourages body cells to take up glucose to store it as glycogen - causes a decrease in blood sugar levels
Function of glucagon
Turns glycogen into glucose in blood
T1 diabetes
Pancreas doesn’t and NEVER does produce insulin
T2 diabetes
Body cells don’t respond to insulin anymore
Hormones when there is too little water in the blood
Pituitary releases ADH, causes kidneys to reabsorb water and there is less urine
Hormones when there is too much water in the blood
Less ADH released, so the kidneys don’t reabsorb water and there is more urine
Function of thyroxine
Controls metabolic rate
How does thyroxine work?
Low levels - hippocampus released TRH - Pituitary releases TSH - thyroid releases thyroxine - faster O2 and food conversion
Function of adrenaline
Controls heart rate, breathing, blood pressure and hastens the conversion of glycogen to glucose
How does adrenaline work?
Released by adrenal gland when a fight/ flight response is triggered
FSH (Found and function)
Released from pituitary gland, stimulates egg maturation and ovary stimulation for oestrogen
Oestrogen (Found and function)
Ovaries, stops FSH production, thickens uterus lining and stimulates the pituitary gland for LH
LH (Found and function)
Pituitary, triggers ovulation
Progesterone (Found and function)
Ovaries, maintains lining
Hormonal contraception
Contains oestrogen and progesterone, so no FSH produced = no egg maturity
Non-hormonal (IUD)
No embryo implantation, physical barrier/ spermicides
Organisation in ecosystems
Individual - Populations - Communities - Ecosystems
Why is interdependence in ecosystems important?
Competition for a limited supply
3 examples of interdependence in ecosystems
Predation, mutualism and parasitism
Location and function of chromosomal DNA
Bacteria, circular coiled molecule of double stranded DNA with no nucleus, carries genetic information to regulate cell processes
Specialised cells have one particular job, what features allow them to undertake this?
Distinct shape, specific chemical reactions in their cytoplasm
How are ciliated cells specialised?
Small hairs, closely packed to protect lungs from infection
How are red blood cells specialised?
Biconcave shape for a larger surface area, haemoglobin and no nucleus
How is a sperm cell specialised?
Haploid nucleus, acrosome and mitochondrial section
General adaptations of a neurone
Elongated, and an ability to conduct chemical signals along the fibre
Specialisation of root hair cell
Elongated for a large surface area for absorption of mineral ions and water from soil
Factors that affect the rate of diffusion
Concentration, temperature, distance, size, surface area
Kidney dialysis machine function?
Using diffusion through a membrane to regulate the composition of the patient’s blood - Removes urea, uric acid and excess salts
What is active transport?
Low conc. to high conc. transport, using ATP gained from respiration, achieved by the assistance of channel proteins in the cell membrane
Daughter cells produced by mitosis
Are genetically identical to each other, are genetically identical to the parent cell which produced them, have the same number of chromosomes as the parent cell
What happens during interphase
The cell grows, the chromosomes in the nucleus are replicated, the cell respires to provide energy for mitosis
How does a bacterium reproduce?
Binary fission
What is the importance of genetically different offspring?
Maintains genetic variation which is essential for natural selection which subsequently ensures the survival of species over time - genetic variety also reduces the rate at which recessive conditions are inherited
Why is sexual reproduction important?
Maintains genetic variety essential for natural selection and the continuation of species - as well as lowering the rate at which recessive conditions are inherited
Why do males need to inherit one Y chromosome for development?
The chromosome contains the genes essential for male development
Why is DNA sometimes called a polynucleotide?
The monomer unit is a nucleotide
How are proteins and enzymes related?
Enzymes are proteins - and a very good example of how specific protein structures have to be as the enzymes have active sites complimentary to their respective substrates - a mutation may change this structure and go on to change the phenotype
Why do most mutations not have an effect on the phenotype of an organism
Large sections of DNA do not code for proteins (introns)
What is a silent mutation?
Mutation that alters the genotype but has no effect on the phenotype (degenerate nature of DNA)
Overall process of gene editing
Gene of interest cut from DNA using restriction enzymes which leave sticky ends of DNA, which match to the sticky ends created on the organism (same restriction enzyme), these are then mixed and hydrogen bonds form to pair the complimentary sticky ends to one another - Ligase is used to join the nucleotides together - This recombinant DNA is inserted into the cell using a Vector
Examples of proteins produced by genetically modified bacteria
Hormones - Insulin
Antibiotics - Penicillin
Enzymes - Rennin for cheese production
Blood clotting factors - VIII for haemophilia
What is a Ti plasmid?
Type of bacterial plasmid that can enter plant cells and insert itself in the genome
Totipotency
Can produce all - including placental - human cells
Pluripotency
Can produce all - except placental - human cells
Multipotent
Specialised to divide only into one type of cell
Risks of stem cell treatment
Cancer development and
rejection by the immune system (transplanted cells are identified as foreign)
What is an iPSC
Induced pluripotent stem cell
Main disadvantage of selective breeding
Reduces genetic variation - less adaptable and higher chance of genetic conditions
What is the induced fit theory
The active site is a specific shape and only catalyses one reaction - the specific substrate alters the shape of the active site when it enters to make the reaction progress more efficiently
Intra and extracellular enzymes
Intra - inside cells and involved with respiration/ photosynthesis
Extra - digestive enzymes that work outside of the cell
What is a reflex arc and what is it used for?
Quick response that omits the processing response of the brain (stimulus, receptor, sensory, relay, motor, effector)
What happens during inhalation?
Intercostal muscles contract and pull the ribs up and outwards.
The diaphragm contracts and flattens downwards.
This increases volume within the thoracic cavity.
This lowers the air pressure inside the thoracic cavity compared to outside the body.
Air from outside the body enters the lungs via the trachea and bronchi to equalise the pressure.
What happens during exhalation?
Intercostal muscles relax and pull the ribs down and inwards.
The diaphragm relaxes and becomes domed.
This decreases the volume within the thoracic cavity.
This reduced volume increases the air pressure inside the thoracic cavity compared to outside the body.
Air from inside the lungs is forced out of the body through the bronchi and trachea to equalise the pressure.
Organs and their blood vessel names
Heart - Coronary
Lungs - Pulmonary
Liver - Hepatic
Kidneys - Renal
Phagocyte function
Ingest or engulf pathogens and digest them using enzymes to prevent damage to body cells.
Lymphocyte function
Produce antibodies, proteins that target antigens on bacteria and viruses, destroying them. Some lymphocytes form memory cells.
What is peristalsis?
Waves of muscular contractions that move food along the oesophagus
2 types of digestion
Mechanical – teeth grinding, stomach churning
Chemical – using bile and enzymes which are produced by specialised cells in glands and tissues in the gut lining.
Excretion organs and their function
Liver - excess amino acids and haemoglobin into bilirubin
Lungs - CO2
Skin - Sweat (not strictly excretory organ)
Kidney - Removal of urea and adjustment of ion/ water content
Path through a kidney
A kidney is composed of three main regions: the cortex, medulla and pelvis.
Blood enters a kidney through a renal artery.
This divides into arterioles and capillaries in the cortex.
Each capillary becomes knotted to form a glomerulus, which is surrounded by a Bowman’s capsule.
This leads to a convoluted tubule. The proximal convoluted tubule passes down into the medulla, where it forms the loop of Henle, returning to a distal convoluted tubule in the cortex again.
The tubule joins a collecting duct, which passes down through the medulla into the pelvis of the kidney.
Function of the nephron
The wall of the capillary of the glomerulus acts as a filter. As the blood enters the glomerulus, its pressure increases.
Large structures (blood cells) and large molecules, e.g. plasma proteins, are retained within the capillary, but smaller molecules (water, dissolved salts (ions), glucose and urea) are forced out by ultrafiltration. This is filtration under pressure.
The filtrate is collected by the renal capsule and passes into the renal tubule.
As the filtrate passes along the tubule, selective reabsorption takes place into the capillaries surrounding the tubule.
Glucose is reabsorbed by diffusion and active transport.
Water is reabsorbed by osmosis, along with some salts by diffusion and active transport to maintain the correct concentration in the blood.
Salts not needed by the body, along with urea and uric acid, continue along the tubule into a collecting duct in the medulla.
The collecting duct delivers the filtrate to the pelvis of the kidney, where the fluid (urine) passes into a ureter to transfer it to the bladder for storage.
Urine is retained in the bladder by a sphincter muscle at its base.
When the sphincter muscle relaxes, the muscle wall of the bladder contracts to expel the urine (a process called urination) through the urethra.
Rising blood glucose triggers
A release of insulin to stimulate the liver to convert glucose to glycogen
Falling blood glucose triggers
Glucagon to convert glycogen stores back into glucose
Low water content
Hypothalamus triggers pituitary to release more ADH and cause more kidney reabsorbtion
Thermoregulation when body is too hot (example of negative feedback)
Arterioles dilate (hypothalamus activated), more sweat and vasodilation
Pituitary gland
Many hormones - can stimulate other glands to release hormones
Thyroid
thyroxine - regulates metabolic rate, HR and temperature
Adrenal gland
Adrenaline - fight/ flight response
Pancreas
Insulin and glucagon - blood sugar regulation
Ovary
Oestrogen and progesterone - menstrual cycle
Low thyroxine…
Hypothalamus releases TRH, pituitary releases TSH and then thyroid releases thyroxine
Adrenaline 4 functions
Stimulates conversion of glycogen to glucose, increases breathing rate, increases HR and stimulates blood flow to muscles
FSH
Produced by pituitary gland and acts on target structures in the ovaries. Stimulates an ovary to develop a follicle containing an egg and to produce oestrogen
Oestrogen
Produced by the ovaries and stimulates the uterus lining to thicken
LH
Produced by the pituitary gland and acts on target structures in the ovary and stimulates the mature follicle to release the egg (ovulation) in the middle of the cycle (around day 14).
Progesterone
Secreted by the corpus luteum and maintains the lining of the uterus during the second half of the cycle so that a fertilised egg may implant
Oestrogen and progesterone inhibit the production of…
LH and FSH
Falling progesterone triggers
Menstruation
Sequence of medical testing
Medicine tested on animals, then phase 1 (few healthy people), then phase 2 (few ill patients) and then phase 3 (double-blind trial using a placebo)
Statin function
They reduce the production of cholesterol, which is a component of atheroma. Build-up of atheroma can lead to blocked arteries.
Anti-coagulants
They reduce the likelihood of blood clotting and therefore blocking an artery.
Anti-hypertensive drugs
They can cause blood vessels to relax so their lumen diameter enlarges, reducing blood pressure.
3 factors that cause the size of the population to change
Food supply, predation and disease (human factors like pollution and climate change also)
Growth stages in the presence of a limiting factor
Lag phase, log phase, stationary phase and death phase
Water cycle processes
Transpiration – plants release water vapour into the atmosphere, mainly through tiny pores called stomata in the leaves. The water evaporates inside the leaf before it is released.
Evaporation – occurs from the surface of bodies of water such as rivers, lakes and the sea.
Condensation – the water vapour in the atmosphere condenses to form clouds.
Precipitation – water in the clouds forms rain, snow, etc. which falls to the land and drains into water systems.
Osmosis – the process used by plant roots, bacteria and other organisms to take up water.
Excretion – from animals. Water is lost from animals in the form of sweat, exhaled air and urine. Faeces (a product of egestion not excretion) also contains some water.
