cell structure 2.1

• what are cells

  smallest functional unit of life
• what are specialised cells

  cells that are adapted to perform a particular function
• what are tissues

  a group of similar cells working together to perform a particular function
• what are organs

  a group of tissues working together to perform a particular function
• what are organ systems

  groups of organs working together to perform a particular function
• examples of eukaryotic cells

  plants, animals, fungi, protists
• which type of cell does not have organ bound organelles

  prokaryotic
• what organelles are in the nucleus

  nucleolus, chromatin, nuclear pore, nuclear envelope
• nucleus

  stores of chromosomes which contain DNA that codes for + regulates the production of proteins by the cell
• what are chromosomes made of

  chromatin

  = (DNA wrapped around proteins called histones)
• what does nucleolus produce

  site of rRNA production +

  makes ribosomes which move out of the nucleus to positions on the RER
• nuclear envelope

  - double membrane

  - controls what substances can enter/leave the nucleus
• nuclear pores

  allow communication + movement of large molecules between cytoplasm + nucleus

  = eg. messenger RNA (mRNA) out, RNA nucleotides in
• what are the 4 bases

  Adenine, Thymine, Guanine, Cytosine
• what are the two different endoplasmic reticulum + similarity

  rough (RER)

  smooth (SER)

  
  

  - ER have folded membranes called cisternae
• function of the RER

  - protein synthesis - has ribosomes on the cisternae

  
  

  - involved with transporting + modifying proteins

  = proteins are packaged into transfer vesicles, which can travel to the Golgi apparatus (for further modification + processing) or the CSM for secretion

  
• structure of rough endoplasmic reticulum (RER)

  - extensive network of flattened, membrane-bound cisternae

  - ribosomes attached to outer surface
• function of the SER

  role in carbohydrate synthesis

  
  

  site of lipid synthesis:

  
  

  - triglycerides = energy storage

  - phospholipids = for making new membrane

  - steroid hormones in some cells

  
• Golgi apparatus function

  1. modification/processing of proteins:- adding carbohydrates to proteins→ glycoprotein- adding lipids to proteins→ lipoprotein

  2. releases vesicles:- secretory vesicles: contain modified proteins (eg. enzymes) + other molecules that are secreted from the cell byexocytosis- lysosomes: specialised vesicles that contain hydrolytic enzymes= used to digest damaged organelles or pathogens

  3. replenishing of cell surface membrane:- empty vesicles made of phospholipids fuse with CSM to allow cell to grow in volume
• lysosomes structure

  specialised vesicles, produced by GA, that contain hydrolytic enzymes called lysozymes enclosed within a phospholipid membrane

  
  

  - bag of digestive enzymes

  = contain 50 different enzymes
• lysosomes function

  - during phagocytosis, lysosomes fuse with phagosomes. the lysozymes then digest + destroy the pathogen

  
  

  - also used to digest + recycle damaged organelles + other cellular debris
• what are phagosomes

  special vesicles containing a pathogen
• mitochondria structure

  - double membrane

  = cisternae

  - inner membrane is folded into cistae

  = increased surface area

  - inner membrane contains electron transport chains + ATP synthase enzymes

  - matrix contains enzymes involved in the link reaction + Krebs cycle

  
• what is the fluid filled centre in the mitochondria called

  mitochondrial matrix
• ribosomes structure

  - very small comprising two subunits made of protein + ribosomal RNA (rRNA)

  - prokaryotic ribosomes new smaller than eukaryotic ribosomes

  
• ribosomes function

  site of protein synthesis=translation
• where are ribosomes found inside cells

  1. floating free in the cytoplasm

  2. associated with the membrane of the RER

  3. inside mitochondria + chloroplast
• vacuole structure

  - large, fluid filled + membrane bound

  - found in all mature plant cells

  
• function of vacuole

  - can increase in size as the cell absorbs water, exerting turgor pressure on the cell wall

  - storage compartment for nutrients + ions

  - temporary store of sugars + AA's
• chloroplast structure

  - double membrane

  - stroma is the site of carbohydrate synthesis

  - folded inner membrane forms the thylakoids (contains chlorophyll). stacks of thylakoids are called grana which are connected by lamellae

  - contains small ribosomes + loops of DNA

  
• chloroplast function

  site of photosynthesis
• what is the cell wall in fungi made of

  chitin

  = a nitrogen containing polysaccharide
• cell wall structure

  plants

  = made of the polysaccharide cellulose

  
  

  - cellulose molecules bundle together to form microfibrils which are laid down in mesh formation

  - fully permeable to water soluble molecules + ions
• cell wall function

  controlled the entrance + exit of molecules
• plasma membrane structure

  - found in all cells

  - made of 2 layers of phospholipids, forming a fluid phospholipid bilayer

  - various proteins are embedded within the PL bilayer

  = these different proteins have specific functions, such as transport of molecules/ions through the membrane or communication/signalling (receptors)
• what are the two different transport proteins

  channel + carrier proteins
• example of a channel protein

  ions, water
• example of a carrier protein

  large polar molecules

  = eg. glucose, AA's
• What does cholesterol do in the cell membrane?

  maintains fluidity
• cell membrane function

  partially permeable

  = allows some substances through but not others