A 2.2 - eukaryotic cell structure

where do eukaryotic cells occur

organisms such as algae, protozoa, fungi, plants and animals

diameter of eukaryotes

5-100 microns

key characteristic of eukaryotics

have a nucleus which contains most of the cell's DNA
The DNA is kept separate from the cytoplasm where most of the cell's metabolic reactions occur

advantages of compartmentalisation

1. enzymes and substrates for a particular chemical reaction can be isolated
2. substances that could damage to the cell can be kept inside the membrane of an organelle
3. conditions such as pH can be maintained at an ideal level for particular reactions
4. organelles with contents be moved around the cell

list the common organelles in eukaryotic cells

cell membrane
endoplasmic recticulum
ribosomes
golgi apparatus
lysosomes
mitochondria
nucleus
chloroplasts (only in plants and algae)
centrosomes
vacuoles

what is the cell membrane composed of?

composed of two layers of lipid molecules (phospholipids) with proteins that can be found on both sides, or through the membrane

what is the cell membrane involved in

import and export of small molecules and ions
cell communication
cell growth by adding new membrane
motility by changing shape

how is the cell membrane involved in cell communication

proteins in the membrane act as receptors to chemical signals in the environment and allows the cell to respond appropriately

where does the cytoplasm occur?

inside the plasma membrane
- organelles are found in this region

cytosol

the fluid portion of the cytoplasm around the organelles

what is in the cytosol

protein filaments that form networks (cytoskeleton) that give the cell its shape and provide a basis for its movements

what are the 3 main types of filaments

actin filaments
microtubules
intermediate filaments

define cilia

tiny hairlike appendages with a bundle of microtubules at their core

what do cilia do

extend from the surface in large numbers
move fluid over the surface of a cell using a back and forth motion

what do protozoa use cilia for

both locomotion and to collect food particles

what do epithelial cells lining the human respiratory tract use cilia for ?

sweep layers of mucus and trapped particles of dust and dead cells to the mouth to be swallowed

flagella

longer than cilia
limited to one or a few per cell
propagate waves along their length, which is used to propel a cell in a particular direction

example of a cell that has a flagella

human sperm cells

where are microvilli found

on epithelial cells lining the small intestine
microscopic appendages created by folds on the cell membrane

what type of filament do mircovilli contain?

actin - which are shorter than microtubules and more rigid

what do microvilli do

increase the surface area over which intestinal epithelial cells can absorb nutrients

what is the endoplasmic reticulum

an extensive network of tubules or channels of membrane

where is the endoplasmic reticulum?

extends from the nucleus

what is the endoplasmic reticulum's function

used to transport materials (proteins and lipids) throughout the internal region of the cell

what is the role of smooth ER is liver cells

involved with the detoxification of drugs

what is the role of smooth ER is ovary cels

production of estrogen (sex hormone)

what is the role of smooth ER in muscle cells

storage of calcium ions for muscle contraction

what does the smooth ER produce

phospholipids for the construction of membranes and lipids for use in the cell

what is a key feature for RER

ribosomes on the exterior of the channels

Where is rough ER found

closer to the nucleus

cisternae

as proteins are produced, they collect in spaces between membranes

function of rough ER

proteins can be transported in vesicles to other parts of the cell such as the golgi apparatus

what are ribosomes composed of

RNA and proteins

difference between ribosomes in eukaryotic and prokaryotic cells

larger and denser

ribosomes are made up of two..

subunits

what are golgi apparatus

flattened sacs (cisternae) which are stacked on top of another

what is golgi apparatus' function

collection, packaging, modification, and distribution of materials for secretion or delivery

what is lysosomes

intracellular digestive centres that arise from the golgi apparatus

structure of lysosomes

- sac bound by a single membrane that contains enzymes for breaking down carbohydrates, proteins, lipids and nucleic acids

shape of mitochondria

rod-shaped, similar in size to bacteria

properties of mitochondria

- double membrane
outer membrane: smooth
inner membrane: folded into cristae
- circular DNA

matrix

fluid in the inner membrane

cristae function

provides a large surface area for chemical reactions that produce useable cellular energy - ATP

what does ATP stand for

adenosine triphosphate

what does the nucleus envelope do?

separates the chromosomal DNA from the cytoplasm

nuclear pores function

allows material to move in and out of the nucleus

nucleus

site of DNA replication and transcription to mRNA

where does ribosome synthesis occur in the nucleus

darkly stained area called the nucleolus

what is DNA in the nucleus associated with

histone proteins - chromatin

chromosomes + cell division relationship

not dividing: uncoiled into chromatin
dividing: condenses into chromosomes

where are chloroplasts found

algae and plant cells

structure of chloroplasts

double membrane - has its own DNA and 70S ribosomes
outer and inner membrane are a continuous layer

what does the third distinct membrane of chloroplasts form?

lamellae or thylakoids

thylakoids

arranged in flattened circular piles called gana + contain pigments for photosynthesis

stroma

fluid found between the grana

what family of organelles do chloroplasts belong to

plastids

what are plastids

double membrane organelles which are responsible for manufacturing food and storing it

amyloplast

accumulates and stores starch

etioplast

produces and stores lipids

proteinoplast

stores proteins

centrosomes structure

pair of centrioles at right angles to one another

centrosomes function

involved in the assembly of microtubules - involved with cell movement and division

where are centrosomes located within the cell

one end of the cell close to the nucleus

what do centrosomes do during cell divison

duplicate

what are vacuoles

storage organelles that are formed from the golgi apparatus
- occupy a large space in plant cells

function of vacuoles

enables cells to have a higher surface area to volume ratio at larger sized

list what vacuoles store

potential food, metabolic waste, toxins and water

what do vacuoles do in plant cells

allows the uptake of water and exerts pressure on the cell wall - provides rigidty

what do cell walls do

provides protection
maintains the shape of the cell
prevents excessive uptake of water

cell wall - whole plant

helps to hold up the plant against the force of gravity

what is the cell wall made of in plants

cellulose polymers wound together

what is the cell wall made of in fungi

chitin