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Edexcel A level Biology : topic 1- 4

This flashcard set covers the whole of topics 1- 4 by spec point. This is mainly for memorization of the key aspects in each topic. It is recommended to learn these facts well before attempting practice question as you will have a general idea of possible answers and questions that could be asked. Hope it helps :)

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why do animals have a heart and circulatory system?

to pump blood around the body so that oxygen can diffuse into cells for respiration

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Edexcel A level Biology : topic 1- 4 - Details



328 questions
Why do animals have a heart and circulatory system?
To pump blood around the body so that oxygen can diffuse into cells for respiration
What are cells?
Cells are the basic units of structure and function in living things
Features of a mass transport system
Network of blood vessels to move through blood as the medium of movement controlled direction and speed by the heart
What are the two types of cells?
Prokaryotes and eukaryotes
Why is a mass transport system important?
Overcomes the limitation of diffusion in larger organisms transports substances around the body allows the exchange of substances to occur
What is the main difference between prokaryotes and eukaryotes?
Eukaryotes = nucleus prokaryotes = no nucleus
Properties of water
Dipolar molecule contains hydrogen bonds high specific heat cohesive good solvent
Why is water dipolar?
Water has a permanent dipole oxygen atom is more electronegative than hydrogen atoms
What are the features of a eukaryotic animal cell?
Nucleus nucleolus ribosomes rER and sER (rough/smooth endoplasmic reticulum) mitochondria centrioles lysosomes Golgi apparatus cell membrane cytoplasm
Why is the polarity of water important?
Allows other polar molecules and ions to dissolve in water
What features are only found in plant cells?
Chloroplasts - site of photosynthesis central vacuole - stores nutrients and supports the cells structure cell wall - support the cell; made of cellulose
What is specific heat capacity?
The amount of heat required to increase the temperature of 1 gram of matter by 1 degree celsius
What is the function of the nucleus?
Stores DNA and controls cellular processes
Why is water's high heat capacity important?
Helps organisms to maintain a constant temperature which is essential for vital process that occur in the body
Why is water cohesive and why is it important?
Strong attraction between water molecules due to its dipolar nature allows it to flow and transport susbstances
Why is water a good solvent?
Water is polar so polar molecules and ions can dissolve in it
What is the function of the rough endoplasmic reticulum?
Membrane bound flattened sacs involved in the folding and release of proteins
What are the blood vessels?
Arteries, veins, capillaries transport blood around the body
What is the function of the smooth endoplasmic reticulum?
Membrane bound flattened sacs produces and metabolises fats and hormones (steroids)
Function of arteries
Carry oxygenated blood away from the heart and to the body tissues (except the pulmonary artery)
What is the function of mitochondria?
Has two membranes; inner membrane folded to form cristae has its own DNA and ribosomes produce ATP (energy) through aerobic respiration for cellular processes
Structure of arteries
Small lumen smooth inner endothelial lining thick layer of smooth muscle cells thick layer of elastic fibre lots of collagen
What is the function of the centrioles?
Spindle formation during cell division found only in animal cells
Functions of veins
Carry deoxygenated blood from the body to the heart (except the pulmonary vein)
What is the function of lysosomes?
Breaks down lipids, carbohydrates and proteins breaking down of waste material only found in animal cells
Structure of veins
Wide lumen inner endothelium lining thinner layer of smooth muscle cells and elastic fibres less collagen valves
What is the function of the Golgi apparatus?
Modifies, packages and secretes proteins made by the rER
How is the structure of capillaries related to its function?
As it is one cell thick it allows for the easy metabolic exchange of substances
What is the function of the cell mebrane?
Phospholipid bilayer protects cell from surroundings provides some shape to the cells
Structure of capillaries
Narrow lumen endothelial cell wall - one cell thick
What is the function of the endothelium in blood vessels?
The smooth passage of blood through arteries and veins short diffusion distance in capillaries
What organelles are involved in protein synthesis?
Nucleus, Golgi apparatus, rough endoplasmic reticulum and ribosomes
What is the function of the smooth muscle cells?
Expand and contract to dilate and constrict the lumen which regulates blood pressure
What are the features of a prokaryotic cell?
Cell wall capsule plasmid flagellum pili ribosomes mesosomes circular DNA
What is the function of elastic fibres in blood vessels?
Stretch and recoil to maintain blood pressure
What is the function of collagen in blood vessels?
To withstand the high blood pressure generated in the blood vessels provides structural support to the vessels
What is the function of valves?
Prevents the backflow of blood they only open one way if pressure is higher behind the valve it opens and if pressure is higher in front of the valve it is closed
Features of the heart
Vena cava left and right atria left and right atrioventricular valves left and right ventricles left and right semi lunar valves pulmonary artery pulmonary vein aorta coronary arteries septum cardiac muscle (made of cardiac cells)
What processes are involved in the cardiac cycle?
Atrial systole ventricular systole diastole
What does the heart do?
The muscle at the centre of the circulatory system that pumps blood around the body
What happens during atrial systole?
The atria contract AV valves are open and SL valves closed pressure in atria increases blood is pushed into the ventricles
What happens during ventricular systole?
Ventricles contract AV valves closed, SL valves open pressure in ventricles increases blood is pushed up into the pulmonary artery (right) and aorta (left)
What happens during diastole?
Heart is relaxed AV valves open pressure in atria begins to increase
How many chambers does the heart have?
4 2 atria and 2 ventricles
What does each side of the heart do?
The right side pumps deoxygenated blood to the lungs the left side pumps oxygenated blood to the body
Explain the relationship between the heart's structure and function
Heart has 4 chambers the right side pumps deoxygenated blood to the lungs the left side pumps oxygenated blood to the body the right side has less cardiac muscle than the left side because the left side has a larger distance to travel therefore generates more pressure the septum divides the left and right sides to stop oxygenated and deoxygenated blood mixing. this
Why does the left side have more cardiac muscle than the right side?
On the left side blood has a longer distance to travel therefore needs to generate higher pressure so that the oxygenated blood can reach all the cells
Why is the septum important?
It divides the left and right sides it prevents the mixing of oxygenated and deoxygenated blood it maintains the concentration gradient of the blood in each side allowing for efficient gas exchange and diffusion
What are sperm?
The male gamete produced in the testes involved in the process of fertilisation
What are the features of sperm?
Flagellum mitochondria acrosome haploid nucleus
What is an egg cell?
The female gamete produced in the ovaries involved in the process of fertilisation
What are the features of an egg cell?
Zona pellucida cortical granules haploid nucleus
What is the function of the flagellum?
To allow the sperm to swim to the egg
What is the function of the mitochondria in sperm?
To provide energy to the flagellum so that the sperm can swim
What is the function of the acrosome?
Contains digestive enzymes that break down the zona pellucida so that fertilisation occurs
What is the function of the zona pellucida?
The protective outer layer of the egg cell
What is the function of the cortical granules?
The organelles that contain enzymes that harden the zona pellucida to prevent polyspermy
What is a haploid nucleus?
A nucleus with half the set of chromosomes gametes each have 23 chromosomes
Outline the process of mammalian fertilisation
Acrosome reaction sperm and egg membrane fusion sperm's nucleus releases and fuses with egg nucleus cortical reaction
Describe the acrosome reaction
Sperm membrane and acrosome membrane fuse together enzymes in the acrosome are released the enzymes break down zona pellucida allowing the sperm and egg membrane to fuse
Describe the cortical reaction
Sperm and egg membrane fuse sperm releases and fuses its nucleus with egg's nucleus to form a diploid (full set of chromosomes) nucleus chemical messages trigger the fusion of the cortical granule membranes and the egg membrane enzymes contained in the cortical granules are released by exocytosis and this hardens the zona pellucida preventing more sperm from fertilising the egg
Similarities between acrosome reaction and cortical reaction
Involve the use and release of enzymes involve the fusion of membranes
Differences between acrosome reaction and cortical reaction
Acrosome digests the zona pellucida; cortical hardens the zona pellucida acrosome is in sperm; cortical granules in egg
What is the locus of a gene?
The location of a gene on a chromosome
Why are sex-linked genetic disorders more common in males?
Males have XY chromosomes whilst females have XX chromosomes the Y chromosome is smaller than the X chromosome this means that the only allele present will be expressed because there is no other allele that can override it
What is the main role of mitosis?
Growth repair asexual reproduction
What happens during prophase?
Nuclear membrane breaks down chromatin condenses into chromosomes
What happens during metaphase?
Chromosomes align themselves at the centre of the cell
What happens during anaphase?
Chromosomes are pulled to opposite poles of the cell by spindle fibres
What happens during telophase?
A nuclear membrane forms around the chromosomes making two new nuclei and separating the chromosomes from the cytoplasm
What is meiosis?
Cell division that produces non identical cells only occurs in gametes
How is genetic variation achieved?
Crossing over (chiasmata) independent assortment
What is crossing over?
The exchange of alleles between homologous chromosomes
What is independent assortment?
The various combinations of ways maternal and paternal chromosomes can be distributed between two daughter cells
Similarities between mitosis and meiosis
Both processes include prophase, metaphase, anaphase and telophase both include cellular division both include the duplication of DNA both involve the production of daughter cells
Differences between mitosis and meiosis
Mitosis divides once but meiosis divides twice 2 daughter cells are made in mitosis and 4 daughter cells in meiosis mitosis occurs in the whole body but meiosis occurs in the gametes daughter cells are identical in mitosis but unidentical in meiosis mitosis cells are diploid but meiosis cells are haploid no crossing over/independent assortment happens in mitosis
What is the cell cycle?
Mitosis cell division that produces genetically identical cells
What are the 3 stages of the cell cycle?
Mitosis cytokinesis interphase
What are the stages involved in mitosis?
Prophase metaphase anaphase telophase
What are carrier proteins?
Membrane protein involved in facilitated diffusion and active transport
What are the properties of gas exchange surfaces?
Surface area to volume ratio concentration gradient diffusion distance
Fick's Law
Rate of diffusion ∝ (surface area x difference in concentration)/thickness of exchange surface
How is the mammalian lung adapted for rapid gaseous exchange?
Large network of capillaries surrounds a lot of alveoli to provide large surface area capillaries and alveoli are each 1 cell thick so short diffusion distance constant blood circulation and breathing maintains concentration gradients
Cell membrane role
Protects the cell from its surroundings controls what enters and exits the cell has receptors that receive chemical messages from other cells to help signal processes that need to occur in the functioning of the whole organism
Structure of a cell membrane
Phospholipid bilayer, channel proteins, glycoproteins, glycolipids, aquaporins, cholesterol
What is the phospholipid bilayer?
The main component of the cell membrane made of hydrophilic phosphate polar heads and hydrophobic fatty acid non-polar tails the heads point outwards whilst the tails point inwards
Meaning of hydrophobic
Does not like water
What are channel proteins?
Proteins integrated into the phospholipid bilayer that allow certain molecules to pass through as they cannot enter the cell by simple diffusion involved in facilitated diffusion
What are glycoproteins?
A carbohydrate chain attached to membrane proteins involved in cell to cell recognition and binding of other molecules
What are glycolipids?
Carbohydrate and lipid chain attached to the phospholipid heads involved in cellular recognition can acts as receptors for viruses
What are aquaporins?
A type of channel protein involved in the transportation of water into and out of cells
What is cholesterol in a cell membrane?
The part protein-part lipid molecule embedded within the phospholipid bilayer that regulate membrane fluidity
What are carrier proteins?
Membrane protein involved in facilitated diffusion and active transport