2.1 Cell structures Flashcards
What is found in a eukaryotic cell
-A nucleus surrounded by a nucleus envelope which contains DNA
-Nucleolus
-Cytoplasm
-A cytoskeleton
-Membrane bound organelles(mitochondria, Golgi apparatus)
-Vesicles
-Ribosomes
What are structures only found in plant cells?
-Cellulose cell wall, large permanent vacuole, chloroplasts
What are structures only found in animal cells
Centrioles and microvilli
What is the function of the nucleus
-It contains DNA so therefore controls protein synthesis and cell metabolic reactions(Enzymes)
What is the function of the nucleolus
-It is responsible for producing ribosomes, RNA forms rRNA(ribosomal RNA) which joins with proteins to form ribosomes.
What is the function of the nucleus envelope.
-Contains gaps so large molecules can move in and out.(mRNA out and hormones in)
- it has a double membrane which protects DNA from damage from cytoplasm and separates the nucleus from the rest of the cell.
What is the structure of the nucleus/ nucleolus/ nucleur envelope?
-Nucleus contains chromatin (histoine proteins+DNA) which is free in the cell when not dividing and tightly coiled when it is, usually only one nucleus per cell
-Nucleolus: contains RNA and ribosomes
-Nucleur envelope: double membraned so protect DNA from damage and has gaps so molecules can diffuse in and out
What is the function of the Rough endoplasmic reticulum
- Its a transport system the cisternae sends proteins made by ribosomes on its surface to the Golgi apparatus for modification and packaging
What is the function of the smooth endoplasmic reticulum
-It contains enzymes which catalase reactions involved with lipid metabolism
-It is involved in lipid and carbohydrate transport, synthesis and absorption.
What is the structure of the Rough endoplasmic reticulum and the smooth endoplasmic reticulum?
-Both networks of membranes with sacs called cisternae, connected to the outer membrane
-In the RER ribosomes are bound to the surface SER doesn’t have any
What is the function of the Golgi apparatus
-Site where proteins are modified and transported
-Proteins can be modified by adding sugar molecules(glycoproteins) or lipid molecules (lipoproteins) and folded into 3D shapes here
-They are also packed into vesicles to be stored in the cell or taken to the plasma membrane to be exported.
What is the structure of the golgi apparatus?
-Flattened sacs enclosing cisternae (similar to RER)
-Secretory vesicles bring material to and from the golgi apparatus
What is the function of mitochondria
-Site of ATP production (aerobic respiration)
-Self replicating so more can be made if a cell needs more energy
-More abundant in cells involed in metabolic activity e.g Liver cells
What is the structure of the mittochondria?
-Double membrane, inner membrane folds to form cristae
-Inner fluid is called matrix (where the krebs cycle takes place)
What is the Function of Chloroplasts
-Site of photosynthesis
-The first stage occurs in the Grana
-Second stage occurs in stroma
What is the function of the Vacuole
-Filled with water and solutes so acts as a storage container
-It helps maintain the cell shape by pushing against the cell wall when the cell is turgid
What is the structure of the chloroplasts/vacuoles?
-Chloroplasts: contain flattened sacs called thylakoids which stack called a granum (joined by lamellae), this is the site where the light-dependant stage of photosynthesis takes place. Contain DNA so can make their own enzymes and self-replicate
-Vacuoles are usually found in plants and are bound by membranes called tonoplasts
What is the function of lysosomes
-Help keep powerful hydrolytic enzymes away from the cell
-Can engulf old organelles and foreign matter and return digested components to cell for reuse
What is the structure of the lysosomes?
-Specialized vesicles created by golgi apparatus
-Contain hydrolytic (digestive) enzymes
-Abundant in phagocytotic cells like macrophages
What is the function of cilia and the flagella/undulipodia
-Airways are lined with cilia to protect from pathogens so therefore cilia is used to move substances outside the cell
-Nearly all cells have one cilium which contains receptors to detect changes in the environment
-Only human cell with a flagella is a sperm cell, this enables it to move.
What is the structure of cilia/flagella?
-Cilia is a hair like structure which is one of the 3 parts of the cytoplasm, contain 9 doublet microtubules surrounding a pair of microtubules (same structure for flagella)
-Flagella is a whip like extension found on the end of a sperm cell
What is the function of a ribosome
-Ribosomes bound to rough endoplasmic reticulum are for synthesising proteins used outside the cell
-Ribosomes found free in cytoplasm are for synthesising proteins that are to be used inside the cell
What is the structure of a ribosome?
-Made in the nucleolus of RNA molecules as two seperate parts which only join after they leave the nucleus
-Not surrounded by a membrane
-Either free in cytoplasm or on RER
What is the function of centrioles
-Aid in cell division by making threads of tubulin that attach to the chromosomes, motor proteins cause the centrosomes(two centrioles at right angles) to rotate and pull the chromosomes to the opposite ends of the cell
-They are also involved in the formation of cilia and undulipodia
What is the function of the cell wall
-Not in animal cells but are found in plant and bacterial cells
-Provide strength and help maintain shape
-Permeable so allow molecules through
What is the structure of centrioles and a cell wall?
-Centrioles consist of two microtubules at right angles. The microtubules are made of tubulin protein subunits and can only be seen during cell division
-Cell walls are located outside the plasma membrane in plants and are made of cellulose and contain gaps called plasmodesmata
What is the structure of the cytoskeleton
-Network of protein threads running through the cytoplasm
-They contain 3 main components which have different functions(microfilaments,microtubules and intermediate fibres)
-microfilaments(7nm in diameter),intermediate fibres(10nm),microtubules(18-30nm)
What is the function of the cytoskeleton
-Microfilaments made of actin are involved in phagocytosis and cytokinesis and help keep the cells strength
-Microtubules determine shape of cytoskeleton and provide tracks for vesicles and form a spindle before the cell divides to bring chromosomes apart.
-Intermediate filaments provide mechanical strength and help with cell signalling by forming special junctions between cells in some tissues
How are proteins made and secreted
1.mRNA is transcribed from a gene
2.this passes out the nucleus pores to the ribosome where a protein is transcribed
3.Proteins go into cisternae of RER and vesicles with the proteins go via microtubules to Golgi apparatus
4.Vesicles fuse and proteins are modified
5.Vesicles travel and fuse to the plasma membrane and are released via excytosis (requires energy)
What are the differences in prokaryotes and eukaryotes
-Prokaryotes don’t have a nucleus whereas eukaryotes do
-Prokaryotes are smaller and have smaller ribosomes
-Prokaryotes are unicellular and have no membrane bound organelles
-Cytoskeleton is less developed(Prokaryotes)
-Prokaryotes have pilli which allow them to exchange with other prokaryotes.
What are motor proteins
-Motor proteins are molecular motors that can move along the cytoplasm
-They also help cell division as they are required to align chromosomes and form the spindles.
