Biology AS OCR Unit 1

Unit 1, Module 1 Of Biology AS OCR
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What type of organisms are made up of prokaryotic cells?
Why type of organisms are made up of eukaryotic cells?
Everything but bacteria
Where does ATP take place in prokaryotes?
In invaginations of the cell membrane called mesosomes.
What is a membrane feature of prokaryotes?
They have only the cell surface membrane and therefore do not contain membrane bound organelles such as mitochondria and chloroplast
What can be found in a prokaryotic cell which is not found in a eukaryotic cell?
Plasmids - very small loops of DNAand a nucleoid - DNA NOT surrounded by a membrane
What is the cell wall of a prokaryote made of?And what is the average size of a prokaryote?
What is the cell membrane of a prokaryote made of?
Phospholipid Bilayer.
What is the size of a eukaryote nucleus?
Name the shell of the nucleus and its function
Nucleur envelope, to seperate DNA from cell content.
What does the outer membrane of the nuclear envelope join with?
Rough Endoplasmic Reticulum
What does the nucleolus contain?
Chromatin, dark staining area of nucleus.DNA coding for rRNA (ribosomal RNA)
Two features and one function of ribosome
Made of rRNA and protein and attached to Rough ER or found free.Protein synthesis
Two features and one function of Rough ER
Consists of flattened membrane bound sacs called cisternae and studded with ribosome.Transports proteins made from attached ribosome - secreted from cell.
Two features and one function of Smooth ER
Consists of flattened membrane bound sacs called cisternae and have no ribosomes.Synthesis of lipids and steroid hormones.
Describe the stages of function of the Golgi Body
Proteins + Lipids move through Golgi body via vesicles budding off one compartment and fusing with one below.
RER -> Cis-Golgi network (returns any proteins wrongly sent to Golgi) -> Stack of cisternae (processes proteins and lipids and directs to destination [into lysosomes]) -> Trans-Golgi (sorts proteins and lipds and directs to destination) -> vesicles
Stack of curved cisternae + Surrounded by many vesicles
Modification of proteins
Features and purpose of lysosomes
Vesicles containing hydrolytic enzymes + spherical sacs surrounded by 1 membraneBreak away from golgi body -> break down substances via phagocytosis.Membranes fuse -> enzymes releasedi.e acrosome to penetrate the egg by sperm cell
Two features and function of MitochondriaDraw and label a diagram
Two membranes seperated by a liquid filled space.Inner membrane highly folded to form cristae (where ATP is generated). Adenosine Triphosphate 2-5um
Features and function of cytoskeleton
Network of fibres made of protein, keep cell's shape stable -> providing an internal framework.
i.e actin filaments move against each other -> move some organelles around inside cell.
Features and function of Undulipodia (flagella) and cillia
Structurally the same, each composed of a cyinder that contains nine doublet-microtubules arranged in a circle with 2 doublets in the centre.
Dynein arms on doublet-microtubules allow for movement. - move due to energy from ATP
Features and function of centrioles
Made up of nine triples of microtubules + occur in pairs at right angles
Organise spindle during cell devision
Cell Wall features and function
Cellulose fibres in strong structure, fully permeable Give cell mechanical strength + prevent over expansion due to water
Vacuole features and function
Sac which fills with water and solutes.Pushes against cell wall to give support.
Chloroplast features and function
Two membranes with fluid filled space.Contain flattened membrane sacs - ThylakoidsStack of thlakoids = a granumChlorophyll molecules in thlakoid membranes.Itergranal lamallae membranes connect granumStroma = jelly like matrix fills chloroplast.Carbohydrated molecules -> CO2 + H20
Ribosome type in Prokaryotic and Eukaryotic cell?
70S for Prokaryotic and 80S for Eukaryotic
What are the steps to protein synthesis?
-DNA copied to mRNA-mRNA leaves through nuclear pore and attatched to ribosome (on RER)-Ribosome reads instructions and uses the codes to synthesise hormone (protein)-Protein in RER pinched off in vesicle -> Golgi body-Golgi body packages and may modify -> packaged into vesicle and moved to cell membrane + secreted outside.
How permeable is the phospholipid bilayer?
Partially Permeable
What are the features of the head?
Phosphate head -> hydrophillic (likes water)
What are the features of the tail?
TWO fatty acid tails -> hydrophobic (dislikes water)
What charge does a phosphate head have?
Negative charge.
What are at least 2 function of a phospholipid bilayer? And state its average size
Act as a barrierSeperate cell organelles from cytoplasmCell recognition and signallingControl the transport of materials in and out of a cell.
7-10nm thick
What is an intrinsic protein?
Protein goes through the bilayer
What is an extrinsic protein?
Protein on the outside of the bilayer
What is the use of cholesterol?
Strengthen PL bilayer and decrease permeability
What is a glycolipid?
Carbohydrates attatched to phospholipid head
What is a glycoprotein?
Carbohydrate attached to protein
What is the use of glyco-proteins/lipids?
Act as chemical/hormone receptors
What can pass through the cell surface membrane?
Water and SOME solutes.
Aquaporins allow for up to 1000 times for permeability to water.
Why is it sometimes said to be a fluid-mosaic model?
Fluid - Phospholipid bilayer can move from side to side freely in plasma membrane
Mosaic - Due to intrinsic, extrinsic and other molecules present (made of different parts)
If a hormone fits in a receptor it is said to be..?
What is cell signalling?
Cells communicating with each other via signals (hormones)
Why might a cell signal?
To communicate.Growth, development, movement.React to external and internal issues.
Define magnification
The degree to which the size of an image is larger than the object itself
Define resolution
The degree to which it is possible to distinguish between two objects very close together.
What resolution and magnification can be reached by a light microscope?
x1500 magnification200nm resolution
What resolution and magnification can be reached by a SEM
(High detail 3D)x100,000 magnification0.1/0.2 nm res
What resolution and magnification can be reached by a TEM?
HD 2Dx500,000 mag0.1/0.2 nm res
What is the equation for magnification and how many um in 1mm
magnification = image/actualactual = image/magnification
1000um in 1mm
Why must a sample be stained?
Light Microscope - Chemicals added to see detailTEM/SEM - Lead salts to scatter electrons different giving contrast
Describe diffusion
The movement of molecules from an areas of high concentration of a molecules to an area of lower concentration. NO ENERGY REQUIRED. Moves down a concentration gradient. Lipid-based and tiny molecules -> through bilayer
Describe facilitated diffusion
Large or charged molecules have to be diffused with facilitation.
How are channel proteins used with facilitated diffusion?
Form pores in membrane - shaped to allow only one type of ion through (gated - can be open or closed)
How are carrier proteins used in facilitated diffusion?
Shaped so specific molecules can fit into them at the membrane surface. Protein changes shape to allow molecule through.
Describe three features of Active Transport
Use metabolic energy (ATP) to change shape of proteinsCan carry against diffusion gradientMuch faster rate than diffusion
Describe features of Endocytosis
Moving large quantities of material inside cell.ATP used to form vesicles and move these around cell.Bulk transport
Describe features of Exocytosis
Moving large quantities of material out of cellATP used againBulk transportCan fuse with or break from cell surface membrane.
What are the passive processes and what does this mean?
No energy required - Osmosis, Diffusion and Facilitated diffusion
What are the active processes and what does this mean?
Energy required in form of ATPActive transport and Exo/Endocytosis
What is osmosis?
Movement of water molecules only by diffusion and across a partially permeable membrane.
Movement from high water potential to lower water potential. Negative to more negative.
What is meant by the term turgid and which cells does this affect?
Plant cellWater moves in to plant cells causing expansion of vacuole, does not burst due to cell wall
What is meant by the term haemolysed and which cells does this affect?
Animal cellsWater moves in to animal cells causing the cell to burst
What is meant by the term plasmolysed and which cells does this affect?
Plant cellsCell membrane palls away from cell wall as water leaves
What is meant by the term crenated and which cells does this affect?
Animal cellsCell shrinks and appears wrinkled as water leaves
In terms of the cell cycle how long is mitosis?
It is short, only a small percent
What stages does interphase contain?
G1, S, G2
What is G1 in the cell cycle?
Growth of the cell in size and increase in organelles
What is S in the cell cycle?
Synthesis of new DNA, chromosomes copied
What is G2 in the cell cycle?
Second growth phase
What are the four stages of mitosis?
What happens in Prophase?
Chromosomes shorten and thicken (supercoil to become visible as two chromatids)Nuclear Envelope dissapearsCentrioles divide into two -> opposite polesProduce microtubules to form spindle
What happens in Metaphase?
Chromosomes arranged in equator of cellAttach to spindle fibres via centromeres
What happens in Anaphase?
Centromere dividesspindle fibres pull one of each to either poleChromatids now called daughter chromosomes
What happens in Telophase?
Daughter Chromosomes reach poles of the cell.Nuclear envelope forms around each group.Lengthen and uncoil.
What happens in Cytokinesis?
Whole cell splits to form two new cells.Animal cell membranes nip.Plant cells - cell plate down middle of spindle to form cell wall
How does yeast reproduce?
Undergo cytokinesis by producing a small 'bud' which nips of the cell -> this is called budding.
Cells which are produced as a result of meiosis are not genetically
Define the term Stem Cell
Undifferentiated cells that are capable of differentiating into multiple possible cells.No hayflick limit
Define differentiation
The development and changes seen in cells as they mature to form specialised cells
What are erythrocytes and what are neutrophils?
Erythrocytes are red blood cells.Neutrophils are a type of white blood cell
Where are blood cells produced?
Undifferentiated stem cells in bone marrow
How do they become erythrocytes?
Nucleus, mitochondria, golgi body and RER, lost and cell becomes biconcave.
How to they become neutrophils?
Keep nucleus, cytoplasm appears granular because of large numbers of lysosomes being produced.
How are the xylem and phloem produced?
Produced from the meristem in the cambium.
How do they become xylem cells?
Produce small cells which elongate, and become reinforced and waterproofed by lignin whilst the ends of the cells break down becoming continuous.
How do they become phloem tissue?
Produce cells which elongate and line up end to end to form a long tube,Ends do not break down completely but form sieve plates between cells
How are erythrocytes specialised?
Contain haemoglobin to attach to oxygen.Loss of organelles means more space .Biconcave shape for larger surface area.
How are neutrophils specialised?
Contain lots of lysosomes which contain hydrolitic enzymes for destroy foreign bodies.
How are sperm cells specialised?
Contain many mitochondria for ATPSperm head contains acrosome to penetrate eggVery small and long for easing movementSingle long undilipodium to propel the cellHalf number of adult chromosomes.
How are squamius epithelial tissue specialised?
Very thin -> decreased diffusion distanceForm smooth flat surface ideal for lining for tubes with fluid.Attached via basement membrane made of collagen and glycoproteins
How are ciliated epithelial tissues specialised?
Cell surface exposed is covered by cilia, which wave in sync to move particles i.e mucus.Cilia waft up mucus to back of throat.Also in ovary to move egg.
How are root hair cells specialised?
Have hair like projection from surface out ointo soil to increase surface area. Uses ATP
How are palisade cells specialised?
Large number of chlorplastsNear top of the leaf for max sun lightCylindrical shape and large surface area allow lots of light to be abasorbed
How are guard cells speciliased?
Control opening and closing of stoma (stomata)Water moved in they become turgid spirals in the walls mean only outer walls stretch so stoma opens
Define the term tissue
A group of similar cells which perform the same particular function
Define the term organ
Collection of tissues which work together to perform a particular function or particular group of functions in a multicellular organism
Define organ system
A group of organs which work together to perform a particular task/function
How are squamous epithelial cells arranged in a tissue?
The cells are held in place by the basement membrane, which is secreted by the epithelial cells. The basement membrane is made of collagen and glycoproteins and attaches the epithelial cells to connective tissue.
How are xylem and phloem arranged in leaf tissue?
CuticleUpper EpidermisPalisade mesophyll cellXylemPhloemSpongy mesophyll cellLower epidermisGuard cellStomaCuticle

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