AQA GCSE Biology

Pregunta	Respuesta
What do muscular tissues do?	Contract to bring about movement.
What do glandular tissues do?	Contain secretory cells that can produce substances such as enzymes and hormones.
What do epithelial tissues do?	Cover the outside of your body and your internal organs.
What do epidermal tissues do?	Cover surfaces and protect them.
What 5 factors affect living organisms?	Nutrients Temperature Amount of light Availability of water Availability of oxygen and carbon dioxide
What physical factors can you measure by counting along a transect?	Light levels Soil pH
Function of a nucleus	Contains genes on chromosomes.
What 2 things happen in the small intestine?	1. Enzymes made in the pancreas flow into here. 2. Soluble food molecules are absorbed into your blood and get transported in the bloodstream.
What 3 things happen in the gut?	1. The muscles of the gut squeeze undigested food onwards into large intestine. 2. Helps break up your food into small pieces with a large SA for enzymes to work on. 3. Mixes food with digestive juices so the enzymes come into contact with as much of the food as possible.
What happens in the large intestine?	Water is absorbed from undigested food into your blood.
What can proteins act as?	Structural components such as muscles and tendons Hormones such as insulin Antibodies, which destroy pathogens. Catalysts in the form of enzymes.
What is a protein?	Protein molecules are made up of long chains of amino acids.
What are enzymes?	large protein molecules
What are enzymes involved in?	1. Building large molecules from lots of smaller ones (e.g. proteins from amino acids) 2. Changing one molecule --> another (e.g. glucose into fructose) 3. BREAKING DOWN LARGE MOLECULES into smaller ones (e.g. insoluble food molecules --> small soluble molecules like glucose)
How do enzymes work?	The long chains of amino acids fold to produce a molecule with a specific shape that allows substrates to fit into the enzyme protein.
Effect of pH on enzyme action	Change in pH affects the forces that hold the folded chains in place, so changes shape in molecule. Active site is lost.
Why do foods need to be digested?	So they can form smaller, soluble molecules that can be absorbed and used by your cells.
Digesting carbohydrates	What breaks it down? Amylase Where is amylase produced? Mouth, small intestine, pancreas. Where is it broken down? Mouth and small intestine. What is it broken down into? Sugars
Digesting proteins	What breaks it down? Protease Where is protease produced? Stomach, pancreas and small intestine Where is it broken down? Stomach and small intestine What is it broken down into? Amino acids
Digesting fats	What breaks it down? Lipase Where is lipase made? Pancreas and small intestine Where is it broken down? Small intestine What is it broken down into? Fatty acids and glycerol
Reasons for respiration	1. Build up large molecules from smaller ones to make new cell material e.g. sugars, nitrates, other nutrients built up into amino acids into proteins. 2. So muscles can contract - so animals can move. 3. Keep bodies at a constant temperature.
The effect of exercise on your body	1. Heart rate increases and arteries supplying blood to your muscles widen. Increases supply of oxygen + glucose to muscles. 2. Increases rate of CO2 and lactic acid being removed from body. 3. Breathing rate increases, more oxygen brought into your body and picked up by red blood cells. 4.
What is anaerobic respiration?	Respiration without oxygen. Glucose is incompletely broken down to form lactic acid.
What is the oxygen debt?	The amount of oxygen needed to oxidise the lactic acid to CO2 and water.
Why does sexual reproduction lead to new varieties of plant?	Gametes join. Mixing of DNA. One copy of each gene comes from each parent.
What is a cell?	The basic building block of a living organism.
What is a nucleus?	The part of the cell that contains genetic info.
What is a chromosome?	A thread-like structure holding genes.
What is DNA?	Chemical from which all chromosomes are made.
What is a gene?	A short section of DNA controlling a characteristic.
What is an allele?	A different version of the same gene.
What is a dominant allele?	An allele that controls the development of a characteristic when it is present on only 1 of the chromosomes.
What is a recessive allele?	An allele that controls the development of characteristics only if the dominant allele is not present.
What is mitosis needed for?	Growth, repair, replacement and asexual reproduction.
Arguments for using stem cells	Offers 1 of the best chances of finding treatments for conditions. Generally uses spare embryos from infertility treatments that would be destroyed anyway. Embryos created from adult stem cells would never become babies. Could use stem cells from umbilical cord blood of newborn babies.
Arguments against using stem cells.	May cause further problems e.g. development of cancers. Unethical - embryos can't give permission to be used in experiments/treatments.
Who was Mendel?	Carried out breeding experiments using peas. First person to suggest separately inherited factors (now called genes). Found that characteristics were inherited in clear+predictable patterns.
Why weren't Mendel's theories accepted?	No-one knew about genes or chromosomes, hadn't seen them through a microscope yet. Insufficient evidence.
What is DNA made up of?	Combos of 4 different chemical bases grouped into 3s. Each group of 3 bases codes for a particular amino acid. Order of bases controls order of amino acids so controls which protein is made.
Homozygous	An individual with 2 identical alleles for a particular characteristic e.g. DD, dd
Heterozygous	An individual with different alleles for a characteristic e,g, Dd
Genotype	Describes genetic makeup of an individual regarding a particular characteristic e,g, Dd, dd
Phenotype	Describes physical appearance of an individual regarding a particular characteristic e,g, dimples, no dimples.
What is polydactyly? Dominant or recessive?	Born with extra fingers or toes. Caused by dominant allele so can be inherited from only 1 parent.
What is Cystic Fibrosis? Dominant or Recessive?	Organs become clogged up by thick, sticky mucus which stops them from working properly. Reproductive system's affected - infertile. Caused by recessive allele.
Arguments for screening embryos	Gives parents a choice on whether or not to keep the baby. Reduces number of people with CF in population. Cures 'disfigurement' (polydactyly) Reduces health care costs
Arguments against screening embrys	Not worth it - polydactyly isn't life-threatening. Could cause miscarriage/damage embryo.
Way that fossils can be formed: Hard parts	Bits that don't decay easily (bones, teeth, claws, shells) form fossils.
Ways that fossils can be formed: Lack of decay	Conditions needed aren't present e.g. 1. Little/no oxygen present 2. Bacteria that causes decay killed off by poisonous gases. 3. Temperature's too low so organisms are preserved in ice.
Ways that fossils can be formed: Replacement	Harder parts of animal/plant replaced by other minerals over a long period of time.
Ways that fossils can be formed: Trace fossils	Fossil footprints, burrows, rootlet traces and droppings are formed.
Why oh why is the fossil record incomplete?	1. Early life forms were soft-bodied so left little fossil trace. 2. Most dead organisms didn't become fossilised because right conditions for fossil formation were rare. 3. Geological activity destroyed many fossils.
causes of extinction	Changes to environment New predators New diseases New + more successful competitors A single catastrophic event e.g. massive volcanic eruption, collision with asteroid.
How a new species arrives	ISOLATION - Species seperated by barrier e.g. mountain, river, ocean, sea. GENETIC VARIATION caused by range of alleles in different environments. NATURAL SELECTION - Advantageous characteristics caused by alleles are 'selected'. SPECIATION - Species become too different to be able to interbreed successfully.
How do fossils provide evidence for the theory of evolution?	They show that things have changed over time. Fossils have similar features to present-day species.
Definition of extinct	All members of a species have died out.
What is a species?	A group of organisms that can breed together successfully.
Why does the stomach produce hydrochloric acid?	1. Enzymes of the stomach work best in acidic conditions. 2. It kills most of the bacteria that you take in with your food.
What does bile do?	1. Stored in gall bladder until it's needed. 2. Neutralises acid from the stomach on the food that's come into the small intestine from the stomach. 3. Emuslifies fats, creating much bigger SA for lipase enzymes to work on.
Sampling Along a Transect	1. Take tape measure/marked rope or string 2. Place quadrat 3. Record the presence of each plant type. 4. Place quadrat at next point (regular intervals) 5. Repeat 3 or more times.
What happens to your food molecules after they've been completely digested?	Leave your small intestine. Pass into your bloodstream... ... to be carried around the body to the cells that need them.
In what 2 places is food NOT digested?	1. The liver 2. The pancreas
Enzymes in the home - Biological Detergents (Explanation, Advantages and Disadvantages)	Proteases and lipases break down proteins and fats in stains. Advantages: Can give a cleaner wash and work better than non-biological detergents at lower temperatures. (So use less electricity) Disadvantages: Can irritate delicate skin
Enzymes in Industry - Baby foods (Explanation, Advantages and Disadvantages)	Proteases can pre-digest proteins in baby foods into amino acids. Advantages - Easier for baby's digestive system to cope, easier to get the amino acids they need from the food. Disadvantages - Allergic reactions
2 Advantages of Using Enzymes in Industry	1. Catalyse reactions at relatively low temperatures and normal pressures - CHEAP TO RUN. 2. Pure enzymes use the substrate more efficiently.
2 Disadvantages of Using Enzymes in Industry	1. Costs to control conditions (keep temperature down and keep pH carefully controlled) 2. Pure enzymes are more expensive to produce.
Ways Enzymes are Used in Medicine: TO DIAGNOSE DISEASE	If you're liver's damaged or diseased, some of your liver enzymes may leak out into your bloodstream. Doctors can test your blood for enzymes to see if your liver's really damaged.
Ways Enzymes are Used in Medicine: TO DIAGNOSE AND CONTROL DISEASE	People with diabetes have a lot of glucose in their blood and their urine. A test strip (containing a chemical indicator and an enzyme) is placed in a urine sample. Enzyme will catalyse breakdown of any glucose in urine. Strip changes colour if products of this reaction are present.
Ways Enzymes are Used in Medicine: TO CURE DISEASE (3 examples)	1. A damaged pancreas cannot make enzymes - take extra enzymes, particularly lipase, to help you digest food. In special capsules so they won't be digested. 2. To reduce damage done to <3 muscle after a <3 attack, enzyme called streptokinase will be injected and dissolve clots in the arteries of the <3. 3. Enzyme can speed up breakdown of a particular amino acid so cancer cells can't get any and die.
How are mitochondria adapted for aerobic respiration?	They have a folded inner membrane to provide a large SA for enzymes involved in aerobic respiration.
How can you tell how active a cell is?	The number of mitochondria in the cell will tell you
What is glycogen and how is it used in the body?	It is a carbohydrate stored in the muscles. It can be converted rapidly back to glucose to use during exercise.
What is glucose used for in aerobic respiration?	Provides the energy to make your muscles contract.
Enzymes in Industry - Syrup	Carbohydrases are used to convert starch into sugar syrup.
How are chromosomes found in body cells?	In pairs
What happens in mitosis?	Copies of the genetic material are made. Cell divides ONCE to form 2 identical body cells.
How many sets of chromosomes do body cells have? How many sets of chromosomes do gametes have?	2 sets 1 set
What happens in meiosis?	Copies of the genetic info are made Cell divides TWICE to form FOUR gametes, each with a single set of chromosomes
What are fossils?	The 'remains' of organisms from many years ago, which are found in rocks.
Word Equation for Anaerobic Respiration	Glucose ----------> Lactic acid (+small amount of energy)
What can fossils show?	How new species are formed How new organisms arise How species become extinct

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