cell structure Flashcards
What is a eukaryotic cell?
- contains membrane enclosed organelles
- have DNA in the firm of chromosomes in the nucleus
What is in the nucleus
- nuclear envelope
- nuclear pores
- chromatin
- nucleolus
What is the role of the nucleus
- largest organelle
- contains DNA, and genetic material
- instructions for cellular processes
- has hereditary information
What is the nuclear envelope?
- double membrane
- protects the content of nucleus from damage in the cytoplasm
What is the nuclear pores?
- allows substances to enter and leave the cell
- mainly allows RNA out bc DNA is too big as well as enzymes and ribosomes
What are chromatin?
- DNA wrapped around histones (proteins) which then condense to make chromosomes
What is the nucleolus
- area in Nucleus responsible for making ribosomes
- composed of proteins and RNA
What is the endoplasmic reticulum
- made of a network of flattened sacs called cisternae
- makes proteins, calcium storage, lipid metabolism, synthesis of carbs and lipids
What is the rough ER
- main site of protein synthesis
- lined with ribosomes => cause its roughness
What is the smooth ER
- responsible for synthesis of carbohydrates and lipids
- detoxification of drugs and toxins
- synthesises lipids such as cholesterol and phospholipids
What is the mitochondria
- the site of aerobic respiration and produces ATP
- has a double membrane and contains own DNA
- Inner membrane folds to form cristae => increases SA => more resp
- releases energy
- contains DNA and ribosomes for replication
What is ATP?
adenosine triphosphate
- stores and releases energy for cellular processes through cellular respiration
What is the cell membrane made of?
- also known as the plasma membrane
- made of lipids and proteins and is formed by phospholipid belayer
- it is partially permeable and controls what enters and leaves the cell
- role in cell signalling = cells detect signals from other cells
What is the golgi apparatus?
- made of cisternae (flattened membranous sacs)
- modifies and processes and packages proteins to be transported
What are Golgi vesicles
- small membrane bound sacs, bud off Golgi apparatus
- transport proteins and lipids to places within the cell or to cell membrane to be secreted
What are lysosomes?
- specialised vesicles that contain enzymes (digestive and hydrolytic)
- break down waste products
- used in phagocytosis
-small organelles filled with enzymes
What is the cytoskeleton?
a network of fibres extending throughout the cytoplasm
- control cell structure and movement
What does the cytoskeleton consist of?
microtubules, microfilaments, intermediate filaments, centrioles
What are microfilaments?
- threadlike structures/fibres made up of a protein called actin
- contractile fibres needed for cytokinesis and cell movement
What are microtubules
hollow structures made up of the protein tubulin, they maintain a cells shape
- act as scaffolding
- dictate shape
- transport system for movement of vesicles and organelles
what are intermediate fibres
- fibres give mechanical strength to cells
- help maintain their integrity.
What are centrioles?
- help organize cell division
- formed from tubulin and located near the nucleus.
- made of microtubules
- two form centrosome = needed for organising spindles in cell division
- in eukaryotic cells apart from flowering plants and fungi
What is in a plant cell?
- nucleus and its contents
- Rough and Smooth ER
- cell wall
- cell membrane
- vacuole
- chloroplast
- Golgi apparatus and vesicles
- ribosomes
- mitochondria
What are chloroplasts?
- have a double membrane
- site of photosynthesis
- contains chlorophyll in thylakoid = trap light
- inner fluid is stroma
- fluid filled membrane sacs are thylakoids
- sacs stack on top of each other to form granum
- photosynthesis takes place in grana and stroma
- contains own DNA and ribosomes
What is the vacuole?
- membrane bound sac
- membrane is called tonoplast = allows certain substances/molecules in
- contributes to growth
— detoxification
- cellular homeostasis
describe the structure of mitochondria
Two phospholipid membranes:
- outer: smooth + permeable to small molecules
- inner: folded, site of electron transport chain, location of ATP synthase
Intermembrane space:
- low pH = high conc of protons
- conc gradient across inner membrane formed during oxidative phosphorylation
Matrix
- aqueous solution within the inner membranes
- Contains ribosomes, enzymes and circular mitochondrial DNA necessary for function
what is division of labour?
- when diff individuals/cells/tissues become specialised to perform complementary tasks that benefit the whole organism
- describes specialised functions of cell organelles which come together to ensure cell is capable of surviving as well as performing role in body
what endosymbiosis?
- where one organism lives within another.
- If the relationship is beneficial to both organisms the engulfed organism is not digested
- to occur one organism must have engulfed the other by the process of endocytosis.
what is endosymbiosis in relation to organelles?
- theory that mitochondria, chloroplasts and other eukaryotic organelles were once free living prokaryotic bacteria
- they were taken into the cell = endosymbiont = organism living inside another
- lead to evolution of eukaryotic cells
- larger anaerobically respiring prokaryote engulfed a smaller aerobically respiring prokaryote (not digested)
- larger prokaryote has a competitive advantage = ready supply of ATP
- gradually the cell evolved into the heterotrophic eukaryotes with mitochondria that are present today
- during evolution, the heterotrophic eukaryotic cell engulfed a smaller photosynthetic prokaryote.
- cell provided a competitive advantage as it supplied the heterotopic cell with an alternative source of energy, carbohydrates
- Over time the photosynthetic prokaryote evolved into chloroplasts and the heterotrophic cells into autotrophic eukaryotic cells
what is the evidence for endosymbiotic theory?
- mitochondria and chloroplasts have similar size to other prokaryotic cells
- they have double membranes
- contains own circular non membrane bound DNA
- both transcribe mRNA from their DNA
(bacteria and mitochondria + chloroplasts)
what is the relationship between organelles in protein synthesis?
- mRNA binds to ribosomes in rough ER and protein chains are made
- can travel through cisternae - packaged into transport vesicles on cytosketeton
- transported to cis-face of golgi body to be modified/packed in golgi vesicles
- transported to trans face of glogi apparatus
- secretory vesicles fuse with cell membrane to release proteins from cells - exocytosis
what are the features of the cytoskeleton?
microtubules
microfilaments
centrioles
intermediate fibres
what are the microtubules?
- 25 nm in diameter
- acts as scaffolding in cell to support cell shape
- acts as tracts for organelle and vesicle movement using ATP
- globular proteins to form tubes, formed from tublins
- α and β tubulin combined to form
dimers, the dimers are then joined into
protofilaments
- Thirteen protofilaments in a cylinder
make a microtubule - make spindle fibres
- make shape of cytoplasm
- tiny cylinders
- can attach to organelles and change length to cause movement
what are the microfilaments?
- used for cell movement + contraction in cytokinesis
- made from contractile protein = actin
what are intermediate fibres?
- more permanent
- mechanical strength and integrity
- play role in cell structure
- anchor organelles in place
what would be a problem of defective cytoskeleton?
cells wont be able to move
