Cell Structure Flashcards
(22 cards)
Nuclear envelope
Nuclear envelope -double membrane that surrounds the nucleus ,continuous with endoplasmic reticulum ,ribosomes on surface ,controls exist and entry of materials in and out nucleus ,contains the reactions taking place in it.
Nuclear pore
Allows passage of large molecules like mRNA out of the nucleus large amount of pores
Nucleoplasm
Granular jelly makes up bulk of nucleus
Chromosomes in nucleus
Consists of protein bound linear DNA
Nucleolus
Small spherical religion within nucleoplasm ,manufactures ribosomal RNA and assembles ribosomes ,there may be more than one nucleolus in a nucleus
Function of the nucleus
Acts as a control centre through the production of mRNA and tRNA and hence protein synthesis
Retains genetic material in the form of DNA and chromosomes
Manufactures ribosomal RNA and ribosomes
Structure of Mitochondrion
Double membrane -controls exist and entry of materials ,inner of the 2 membrane folders into cristae which provide large SA for attachment of enzymes and other proteins involved in respiration.
Matrix- makes up remainder of structure ,contains protein,lipids,ribosomes,DNA, that allow mitochondria to control production of some of its own proteins,enzymes involves in respiration found in matrix
Role of mitochondrion
Sites of Aerobic respiration ,responsible for ATP production from respiratory substrates like glucose ,number ,size and amount of Cristae depend on metabolic activity of cell
Chloroplast envelope
Double plasma membrane highly selective
Grana ,thylakoids ,stroma
Grana-stacks of 100 disc structures called thylakoids ,within thylakoids contain chlorophyll , first stage of photosynthesis occur in grana
Stroma-fluid filled matrix where second stage of photosynthesis occurs,within stroma there are starch grains.
How are chloroplasts adapted to their function of harvesting sunlight and carrying out photosynthesis
Granal membranes -large SA for attachment of chlorophyll ,electron carriers and enzymes that carry out first stage of photosynthesis
Fluid of stroma -possesses all enzymes needed to make sugars in second stage of photosynthesis
Chloroplasts contain DNA and ribosomes so can easily manufacture proteins for photosynthesis
What is the endoplasmic reticulum
3 dimensional system of sheet like membranes spreading throughout the cytoplasm , its continuous with the outer nucleus membrane ,the membranes encloses a network of tubules and flattened sacs called Cisternae, RER AND SER
RER
Has ribosomes on outer surface
Provides large SA for protein synthesis and synthesis of glycoproteins
Provides pathway for transport of materials especially proteins throughout cell
SER
No proteins on surface
Synthesises stores and transports lipids and carbohydrates
Golgi apparatus structure
More compact than SER
Consists of a stack of membranes that make up flattened sacs called cisternae ,with vesicles
Vesicles move to surface where they fuse with cell membrane and release their contents outside
Functions of Golgi
Add carbohydrates to proteins -glycoproteins
Produces secretory enzymes such as those secreted by pancreas
Secretes carbohydrates such as those making cell walls in plants
Transports modifies and stores lipids
Forms lysosomes
How are Lysosomes formed
Formed when the vesicles of the Golgi apparatus contains enzymes such as protease and lipase
Function of lysosomes
Hydrolyse material ingested by phagocytic cells such as white blood cells and bacteria
Releases enzymes outside cell to destroy material around cell (exocytosis)
Digest worn out organelles so useful chemicals can be reused
Break down cells after they die (autolysis)
Ribosomes
May be found on RER or cytoplasm
80s-eukaryotic cells
70s -prokaryotic cells and in mitochondria and chloroplasts
Has 2 subunits -one large one small,each contain ribosomal rna and protein,they are site of protein synthesis
Cell wall structure
Consists of microfibrils of the polysaccharide cellulose embedded in a matrix ,microfibril give strength ,thin layer called lamella
Cel wall function
Provides mechanical strength to prevent bursting under pressure ,strength to plant as a whole,allows water to pass along so contributes to water movement
Cells walls of fungi don’t have cellulose they have chitin
Vacuoles
Fluid filled sac bounded by single membrane called tonoplast
Contains solutions of mineral salts,sugars,amino acids and wastes and pigments
Supports herbaceous parts of woody plants by making cells turgid
The sugars and amino acids may act as temporary food store
Pigments may colour appeal to attract pollinating insects
