Cell structure - inside a cell, protein secrection

Question 1

what are the membrane and non-membrane organelles?

Answer 1

membrane:
-nucleus/nuclear envelope/nucleolus
-rough endoplasmic reticulum (RER)
-smooth endoplasmic reticulum (SER)
-golgi apparatus
-mitrochondria
-chloroplasts
-vacuole
-lysosomes
-cilia and undulipodia

non-membrane:
-ribosomes
-centrioles
-cytoskeleton
-cellulose cell wall

Question 2

membrane organelles:
what is the structure of chloroplasts?

Answer 2

large organelle, 4-10 micrometers long
found only in plant cells and in some protocists

surrounded by a double membrane/envelope
inner membrane is continuous with stacks of flattened membrane sacs called thylokoids (resembling piles of plates), which contains chlorophyl
each stack/pile of thylakoids is called a granum
the fluid-filled matrix called stroma
chloroplasts contains loop of DNA and starch grains

Question 3

membrane organelles:
what is the function of chloroplast?

Answer 3

site of photosynthesis
1st stage of photosynthesis=when light energy trapped by chlorophyll and used to maek ATP, occurs in grana. water is split to supply hydrogen ions
2nd stage of photosynthesis=hydrogen reduces CO2, using energy from ATP to make carbohydrates, occurs in stoma. chloroplasts are abundant in leaf cells, particulary the palisade mesophyll layer

Question 4

membrane organelles:
what is the structure of mitrochondria?

Answer 4

maybe be spherical, rod-shaped or branched
2-5 micrometers long

surrounded by 2 membranes with a fluid-filled spare between them - inner membrane highly folded into cristae
inner part of mitrochondrian is fluid- filled matrix

Question 5

membrane organelles:
what is the function of mitrochondria?

Answer 5

site of ATP (energy currency) production dring aerobic respiration
self -replicating - more cells are made if cells energy needs increase
they’re abundant in cells where much metabolic activity takes place
e.g.in liver cells and at synapses between neurones where neurotransmitter is synthesised and released

Question 6

membrane organelles:
what is the structure of the golgi apparatus?

Answer 6

consists of a stack of membrane-bound flattened sacs. Secretory vesicles bring materials to ans from the golgi apparatus

Question 7

membrane organelles:
what is the function of golgi apparatus?

Answer 7

protein are modified by:
-adding sugar molecules to make glycoproteins
-adding lipids molecules to make lipoproteins
-being folded into 3D shapes
protein packages into vesicles that are pinched off and then:
-stored in cell
-or, moved to the plasma membrane, either to be incorporated into the membrane or exported out of cell

Question 8

membrane organelles:
what is the structure of the smooth endoplasmic reticulum (SER):

Answer 8

system of membrane, containing fluid-filled cavities (cisternae) thats continuous with nuclear membrane
no ribosomes on its surface

Question 9

membrane organelles:
what is the function of the smooth endoplasmic reticulum (SER)?

Answer 9

SER contains enzymes that catalyse reactions involves with lipids metabolism, such as:
-synthesis of cholesterol
-synthesis of lipids/phospholipids needs by cell
-synthesis of steroids hormones
Involved with aborption, synthesis and transport of lipids (from the gut)

Question 10

membrane organelles:
what is the structure of the rough endoplasmic reticulum (RER)?

Answer 10

a system of membranes, containing fluid-filled cavities (cisternae) that’s continuous with nuclear membrane
coated in ribosomes

Question 11

membrane organelles:
what is the function of the rough endoplasmic reticulum (RER)?

Answer 11

RER is the intracellular transport system: the cisternae form channels for transporting substances form one area of cell to another
Provides large surface area for ribosomes, assembles amino acids into proteins
-then actively pass through membrane into cisternae and transported to golgi apparatus for modification and packaging

Question 12

membrane organelles:
what is the structure of nucleolus/nucleus/nuclear envelope?

Answer 12

surrounded by double membrane called nuclear envelope
-there are pores in nuclear envelope

nucleolus doesn’t have a membrane
-contains RNA

chromatin is genetic material, consisting of DNA around histone protein
-when cell not dividing, chromatin spreads out/ extended
-when cell about to divide, chromatin condenses and coils tightly into chromosomes
-makes up nearly all organisms genome

Question 13

membrane organelles:
what is the function of nucleolus/nucleus/nuclear envelope?

Answer 13

nuclear envelope separates contents of nucleus from rest of cell
In some regions outer and inner nuclear membrane fuse together. At these points some dissolved substances and ribosomes pass through
Pores enable large substances (messenger RNA -mRNA) to leave nucleus. Substances (steriod hormones) may enter nucleus, from cytoplasm by pores

nucleolus where ribosomes made
chromosomes contains organisms’s genes

nucleus: control centre of cell, stores organism’s genome, transmit genetic info, instructions for protein synthesis

Question 14

membrane organelles:
what is the structure of the vacuole?

Answer 14

surrounded by a membrane called the tonoplast and contain fluid

Question 15

membrane organelles:
what is the function of the vacuole?

Answer 15

only plant cells have large permanent vacuole
filled with water and solutes and maintains cell stability, because when its full, it pushes against cell wall, making cell turgid
If all plant cells are turgid then this helps support the plant, especially in non-woody plants

Question 16

membrane organelles:
what is the structure of the lysosomes?

Answer 16

Small bags, formed from golgi apparatus. each is surrounded by a single membrane
Contain powerful hydrolytic (digestive) enzymes
Abundant in phagocytic cells (e.g. neutrophils adn macrophages) - types of white blood cells - that can ingest and digest invading pathogens (e.g.bacteria)

Question 17

membrane organells:
what is the function of the lysosomes?

Answer 17

keep the powerful hydrolytic enzymes separate from rest of cell
can engulf old cell organelles and foreign matter, digest them and return then digested components to cell for reuse

Question 18

membraen organelles:
what is the structure of cilia and undulipodia?

Answer 18

theres protrusions from cell and surrounded by cell surface membrane
each contains microtubules
they’re formed from centrioles

Question 19

membrane organelles:
what is the function of the cilia and undulipodia?

Answer 19

Epithelial cells lining your airways each have mnay hundreds of cilia that beat and move band of mucus
Nearly all cell types in body have 1 cilium that acts as an antenna. contains receptors and allows cell to detect signals about its immediate environment
One type of human cell to have an undulipodium (longer cilium) is a spermatozoon. The undulipodium enables the spermatozoon to move.

Question 20

non-membrane organelles:
what is the structure of the cytoskeleton?

Answer 20

network of protein structures within cytoplasm. consists of:
-rod-like microfilaments made of subunits of protein actin; they’re polymers of actin and each microfilament about 7nm in diameter
-intermediate filament about 10nm diameter
-straight, cylindrical microtubules (made of protein subunits called tubulin)about 18-30nm diameter
-cytoskeleton motor protein, myosins, kinesins and dyneins, are molecular motor
-they’re enzymes and have site binds to and allows hydrolysis of ATP as their energy source

Question 21

non-membrane organelles:
what is the function of the cytoskeleton?

Answer 21

protein microfilaments within cytoplasm give support and mechanical strength, keep cell’s shape and allow cell movement
microtubules provide shape and support cells, help subsatnces and organelles to move through cytoplasm in cell

-form the track along which motor protein (dynein and kinesin) walk and drag organelles from 1 part of cell to another
-form spindle before cell divides. spindle threads anable chromosomes to be moved in cell
-microtubules make up cilia, undulipodia and centriole
Intermediate filaments makes variety of proteins.they:
-anchor nucleus in cytoplam
-extend between cells in some tissues, between special junctions, enables cell-cell signalling, allows cells to adhere to membrane , therefore stablising tissue

Question 22

non-membrane organelles:
what is the structure of ribosomes?

Answer 22

small spherical organellels - about 20nm diameter
made of ribosomal RNA
made in nucleolus, as 2 separate subunit, which pass through nuclear envelope into cell cytoplasm and then combine

Some remain free in cytoplasm and some attach to the endoplasmic reticulum

Question 23

non-membrane organelles:
what is the function of the ribosomes?

Answer 23

bound to the exterior of RER are mainly for synthesising protein that will be exported outside cell
ribosomes that are free in cytoplasm, either singly or in clusters are primarily site of assembly of protein that will be used cell

Question 24

non-membrane organelles:
what is the structure of centrioles?

Answer 24

centrioles consists of 2 bundles of microtubules at right angles to each other
microtubules made of tubulin protein subunits and arranged to form a cylinder

Question 25

non-membrane organelles:
what is the function of centrioles?

Answer 25

Before cell divides, the spindle, made of threads of tubulin, forms from centrioles
Chromosomes attach the middle part of spindle and motor proteins walk along the tubulin threads, pulling the chromosomes to opposite ends of cell
Involved in formation of cilia and undulipodia:
-before cilia form, centrioles multiply and line up beneath cell surface membrane
-microtubules sprout outwards from each centrioles, forming cilium/undulipodium

presents in some unicellular green algae - not in cells of (higher plants)

Question 26

non-membrane organellels:
what is the structure of cellulose cell wall?

Answer 26

the cell wall of plants is on outside of plasma membrane
it is made from bundles of cellulose fibres

Question 27

non-membrane organelles:
what is the function of cellulose cell wall?

Answer 27

absent from aniumal cells, cell wall is strong and prevent plant cells bursting when turgid (swollen)
cell walls of plant cells:
-provide strength and support
-maintain cell’s shape
-contribute to strength and support of whole plant
-permeable and allow solutions (solute and solvent) to pass through

Question 28

whats in a eukaryotic cell?
(animal,plant,fungal and protoctists)

Answer 28

nucleus srrounded by nuclear envelope and containing DNA organises and wound into linear chromosomes
inside nucleus called nucleolus (conatin RNA, chromosomes unwind)
-nucleolus involved in making ribosomes
jelly-like cytoplasm - in which organelles are suspended
cytoskeleton- network of protein filament within cytoplasm, organelles move
-allow some cells to move and allow contraction of muscle cells
plasma membrane
membrane bound organelles
small vesicles
ribosomes- organelled with membranes
-proteins assembled there

Question 29

what do prokaryotic cells have?

Answer 29

plasma membrane
cytoplasm
ribosomes (amino acid to proteins)
DNA and RNA
protective waxy capsule (around cell wall)
small loops of DNA (plasmids)
flagella - long whip projections that enable them to move
pili - smaller hair-like projections that enbale bacteria to adhere allow passage of plasmid DNA from 1 cell to another
much smaller
less well-developed cytoskeleton with no centrioles
doesn’t have nucleus/cell membrane bound organelles
have a wall amde of peptidoglycan and not cellulose
smaller ribosomes
naked DNA thats not wound around histone protein but floats free in cytoplasm, as a loop

Question 30

what is the process of the production and secrection of protein?

Answer 30

1)mRNA is a copy of the gene (instructions) made in nucleus
2)mRNA leaves nucleus through nuclear pores
3)mRNA attaches to ribosomes and enters though the rough endoplasmic reticulum
4)then leaves ‘punched off’into a vesicle (has an amino acid inside) and travels to golgi apparatus
5)vesicle fuses with golgi apparatus and turns from primary structure of amino acids to a tertairy structure (processed and packaged)
-more than 1 polypeptide in, means they will form the teritiary structure and then come together to form quaternary structure
6)then ‘pinched off’ into another vesicle, travels to plasma membrane (formed into a protein inside)
7)vesicle fuses with plasma membrane
8)plasma membrane opens to release the molecule/protein to the outside - this is called exocytosis, where the vesicle fuses with membrane. Or the protein can become part of cell membrane.