Cells Flashcards
What carries out all the functions of life?
Unicellular organisms
Outline the Cell Theory
All living organisms are composed of cells. Cells are the smallest unit of life. Cells come from pre-existing cells and can not be created from non-living material.
What is the relative size of a molecule?
1nm
What is the relative thickness of the cell membrane?
10nm
What is the relative size of a virus?
100nm
What’s the relative size of a bacteria?
5micrometres
What is the relative size of organelles?
Up to 10micrometres
What is the relative size of eukaryotic cells?
100micrometres
How do you calculate the linear magnification of drawings and the actual size of specimens in images of known magnification?
Magnification = length of drawing / length of actual specimen
How does the surface area to volume ratio limit the cell size?
When a cell grows the volume increases faster than the surface area leading to a smaller surface area to volume ratio. If it gets too small, substances won’t be able to enter the cell quick enough to fuel reactions and waste products will start to accumulate within the cell as they will be produced faster than they can be excreted.
What organisms show emergent properties?
Multicellular organisms show emergent properties
How might a cell increase it’s SA:V ratio?
1) throw out extensions (villi in the small intestine) 2) flatten into a thin form 3) divide the cytoplasm into smaller volumes
What are emergent properties?
It means that cells can differentiate into specialised cells and these specialised cells can interact with each other (cells, tissues, etc).
What are stem cells?
Stem cell is an unspecialised cell that has retained the ability to divide and have the ability to differentiate along different pathways
How do cells carry out specialised functions?
Cells in multicellular organisms differentiate to carry out specialised functions by expressing some of their genes and not others. This is called differentiation. Differentiation depends on gene expression which is regulated mostly during transcription.
What is the function of the cell wall?
Protects the cell from the outside environment and maintains the shape of the cell. It also prevents the cell from bursting if internal pressure rises.
Outline one therapeutic use of stem cells.
Define stem cells. Stem cells are derived from human embryos, left over from the placenta or IVF and new techniques have developed that mean diseased or dysfunctional cells can be replaced with healthy functioning ones. Bone marrow transplants. Stem cells found in the bone marrow give rise to the red blood cells, white blood cells and platelets in the body. These stem cells can be used to treat certain types of cancer, such as leukaemia. Chemotherapy kills the normal cells in the bone marrow so the patient cannot produce blood cells. After chemo, patient will have a bone marrow transplant where stem cells are transplanted back into the patient through a drip. These stem cells will start producing blood cells. Allows patients to undergo high doses of chemotherapy
What is the function of the Plasma Membrane in a bacteria cell?
Semi-permeable membrane that controls the substances moving in and out of the cell. It controls integral and peripheral proteins. Substances pass through by either active or passive transport.
What is the function of the cytoplasm in a bacteria cell?
Contains many enzymes used to catalyse chemical reactions of metabolism and it also contains the DNA in a region called the nucleotide. Ribosomes are also found in the cytoplasm.
What is the function of the Pili in a bacteria cell?
Help bacteria adhere to each other for the exchange of genetic material
What is the function of the flagella in a bacteria cell?
Made of a protein called flagellin. Helps bacteria move around by the use of a motor protein that spins he flagellum like a propeller.
What is the function of the ribosomes?
They are the sight of protein synthesis. Contributes to protein synthesis by translating mRNA.
What is the function of a nucleoid in a prokaryotic cell?
Region containing naked DNA which stores hereditary material that controls he cells and will be passed onto daughter cells.
How do prokaryotic cells divide?
Binary Fission. Binary Fission is a method of asexual reproduction involving the splitting of the parent organism into two separate organisms.
What is the function of the ribosomes in a eukaryotic cell?
Found either floating free in the cytoplasm or attached to the surface of the rough endoplasmic reticulum and in mitochondria and chloroplasts. Ribosomes are the site of protein synthesis as they translate mRNA to produce proteins.
What is the function of the rough endoplasmic reticulum in a eukaryotic cell?
Can modify proteins to alter their functions and/or destinations. Synthesises proteins to be excreted from the cell.
What is the function of the lysosomes in a eukaryotic cell?
Contains many digestive enzymes to hydrolyse macromolecules such as proteins to their monomers.
What is the function of the Golgi apparatus in the eukaryotic cells?
Receives proteins from the rough endoplasmic reticulum and may modify them further. It also packages proteins before the protein is sent to its final destination which may be intracellular or extra cellular.
What is the function of the mitochondria in a eukaryotic cell?
It is responsible for aerobic respiration. Converts chemical energy into ATP using oxygen.
What is the function of the nucleus in a eukaryotic cell?
Contains the chromosomes and therefore the hereditary material. It is responsible for controlling the cell.
Compare prokaryotic and eukaryotic cells.
1) prokaryotic cells have naked DNA in the nucleoid. Eukaryotic cells have chromosomes that are made up of DNA and proteins in the nucleus. 2) eukaryotic cells have mitochondria whereas prokaryotic cells don’t 3) prokaryotic cells have small ribosomes (70S) whereas eukaryotic cells have large ribosomes (80S)
State three differences between plant and animal cells.
1) Animal cells have a plasma membrane and no cell wall whereas plant cells have a plasma membrane and a cell wall. 2) Animal cells do not have chloroplasts whereas plant cells do 3) Animal cells store glycogen as their carbohydrate resource whereas plant cells store starch
Outline two roles of extra-cellular components?
Plant Cell Wall - gives the cell strength and prevents it from bursting under high pressure as it is made up of cellulose. Gives the cell shape, prevents excessive water take up by osmosis and is the reason why the whole plant can hold itself up against gravity. Bone Matrix - a network of calcium based compounds that give the bone it’s strength and structure
How do the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes?
Draw a diagram of phospholipid bilayer. The phospholipids are held together by hydrophobic interactions and are stabilised by the interaction of hydrophillic heads and surrounding water. Phospholipids allow for membrane fluidity,and phospholipids with unsaturated fatty acids are more fluid, which allows the membrane to break and reconnect, allowing processes like exocytosis.
What is diffusion?
Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration.
What are the functions of membrane proteins?
Can act as hormone binding sites, electron carriers, pumps for active transport, channels for passive transport and also enzymes. Can be used for cell to cell communication.
What is osmosis?
Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.
What is simple diffusion?
Passive transport happens by simple diffusion (and facilitated diffusion). Simple diffusion involves he diffusion of molecule through the phospholipid bilayer. Molecules will go from a region of high concentration to a region of low concentration and will eventually become evenly distributed if they are permeable to the membrane.
What is facilitated diffusion?
Passive transport happens by facilitated diffusion (and simple diffusion). Facilitated diffusion involves the use of channel proteins embedded in the membrane. Molecules will go from a region of high concentration to a region of low concentration and will eventually become evenly distributed if they are permeable to the membrane.
What is used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane?
Vesicles
Describe the process of active transport.
moves substances up/against a concentration gradient / from lower to higher concentration;
protein/pump (in membrane) that moves material;
ATP is used to change shape of the protein pump, depositing substance onto other side of the membrane
What are vesicles used to transport materials within a cell between?
The rough endoplasmic reticulum, Golgi apparatus and plasma membrane
How do vesicles transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane?
Vesicles carry the protein from the rough endoplasmic reticulum (after it has been synthesised) bud off the RER and transport it to the Golgi apparatus to be further modified. After this he vesicles carrying the protein bud off the Golgi apparatus and carry the protein to the plasma membrane. The vesicle then fuses with the plasma membrane expelling their contents outside the cell. Membrane returns to its original state. Process called exocytosis. Endocytosis is a similar process involving the pulling of the plasma membrane inwards so that the pinching of the vesicle from the plasma membrane occurs and then his vesicle can carry its content anywhere in the cell.
What does the fluidity of the membrane allow it to do?
Change shape, break and re-form during endocytosis and exocytosis.
Describe how the structure pf the membrane allows the formation of vesicles.
fluidity of membrane allows change of shape/invagination/formation of vesicles;
phospholipids can move / phospholipid bilayer makes membrane fluid/flexible;
weak bonding between phospholipid tails;
cholesterol affects membrane fluidity.
What are the three stages in the cell cycle, in order?
Interphase (G1, Synthesis, G2), Mitosis (Prophase, metaphase, anaphase, telophase), and cytokinesis
What happens during mitosis in the cell cycle?
Mitosis is divided up into prophase, metaphase, anaphase and telophase. The spindle fibres attach to the chromosomes and pull sister chromatids apart. This stage serape rates the two daughter genomes.
What happens during interphase in the the cell cycle?
Interphase is an active period in the life of a cell, when many metabolic reactions occur, including protein synthesis, DNA replication, and an increase in the number of mitochondria and/or chloroplasts. G1 - cell grows larger Synthesis - genome is replicated G2 - second growth phase, separates the newly replicated genome and marks the end of interphase
What happens during cytokinesis in the cell cycle?
The cytoplasm divides to crate two daughter cells. In animal cells the cell is pinched in two while plant cells from a plate between the dividing cells.
What are tumours the result of? Where can they occur?
Tumours are he result of uncontrolled cell devision and they can can happen in any organ or tissue.
What metabolic reactions occur during interphase?
Protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts
What are the four stages of mitosis in order?
Prophase Metaphase Anaphase Telophase
What happens during the Prophase phase of mitosis?
The spindle micro tubules grow and extend from each pole to the equator. Also chromosomes super coil and become short and bulky and the nuclear envelope breaks down.
What happens during the Metaphase phase of mitosis?
The chromatids move to the equator and the spindle micro tubules from each pole attach to each centromere on opposite sides.
What happens during the anaphase phase of mitosis?
The spindle micro tubules pull the sister chromatids apart splitting the centromeres. This splits the sister chromatids into chromosomes. Each identical chromosome is pulled to opposite poles.
What happens during the telophase phase of mitosis?
The spindle micro tubules break down and the chromosomes uncoil and so are no longer individually visible. The nuclear membrane reforms. The cell them divides by cytokinesis to form two daughter cells with genetically identical nuclei.
What involves mitosis?
Growth, embryonic development, tissue repair and asexual reproduction
How does mitosis produce genetically identical nuclei?
During interphase, the DNA replicates and produces two copies of identical genetic material known as sister chromatids, which are held together by a centromere. Sister chromatids are separated during mitosis to form two genetically identical nuclei: in prophase chromosomes shorten and thinken and begin to move towards the centre; in metaphase they line up at the equator separately (not in homologous pairs); at the start of anaphase, centromeres divide separating sister chromatids, which are pulled to opposite poles of the cell. Nucleur envelope forms around each set of chromosomes.
What exceptions are there to the cell theory?
Skeletal muscles are larger Fungal hyphae are sometimes not divided up into individual cells Some tissues or organs contain large amounts of extra cellular material eg mineral deposits in bone
Outline the differentiation of cells in multicellular organisms.
Differentiation is development in specific ways. Cells carry out specialised functions. Cells have all genes and could develop in any way. In differentiation, some genes are expressed but others are not. The cell’s position, hormones, cell to cell signal and chemicals will determine how a cell develops. A group of differentiated cells is a tissue.
Draw and label a diagram of the ultra-structure of Escherichia Coli (E. coli) as an example of a prokaryote.
Include: Cell wall, capsule, slime layer Plasma membrane Mesosome Cytoplasm Ribosomes nucleoid contatining naked DNA flagella pilli plasmid
E. coli is an example of what type of cell?
Prokaryote
Draw and label a diagram of the ultra-structure of a liver cell as an example of an animal cell.
Include: Nucleus surrounded by nucleus membrane Mitochondria Rough endoplasmic reticulum Golgi Apparatus Ribosomes attached to RER and free ribosomes in the cytoplasm Lysosome Plasma membrane
Draw and label a diagram to show the structure of membranes.
Include: A double layer of phospholipid molecules (with hydrophobic tails and hydrophyllic heads) An integral protein (passing completely through the lipid bilayer) A peripheral protein (shown on the surface and not penetrating the lipid bilayer) A glycoprotein (an integral protein with an attached carbohydrate chain) Cholesterol as a component in the bilayer
Explain how vesicles are used in cells, including the way in which they form and are reabsorbed.
Vesicles are made by pinching off a piece of the membrane, which is facilitated by the fluidity of the membrane. This vesicle can then be used to transport materials around inside cells, for example proteins from the RER to the Golgi apparatus, to the plasma membrane. Endocytosis/Phagocytosis is the absorption of a material using a vesicle and the fusion of a vesicle with plasma membrane allows material to be passed out. Exocytosis is the secretion of a material using a vesicle.
What are tumours the result of?
Uncontrolled cell division which can occur in any organ or tissue
Outline the process of endocytosis.
Endocytosis is the mechanism whereby cells take in solids of solutions, through the involvement of the formation of vesicles. It is an active process. It is more specifically called phagosytosis when solids are engulfed and pinocytosis when solutions are taken in, in which the vesicles are much smaller.
