Chapter 2 Cell Structure

• Draw a diagram of an animal cell

  Animal Cell

  
• Draw a diagram of a Plant cell

  Plant cell

  
• How do plant cell differ from animal cells

  -Cell wall with plasmodesmata (small channels for exchanging substances with adjacent cells)

  -A vacuole containing cell sap

  -Chloroplasts
• What is the function of a plasma membrane?

  Regulates the movement of substances into and out of the cell. It also has receptor molecules on it, which allows it to respond to chemicals like hormones.
• What is the function of the Cell Wall?

  Provides support for plant cells
• Describe the structure of the nucleus

  A large organelle surrounded by a nuclear envelope (double membrane) which contains many nuclear pores. The nucleus contains chromatin (made from DNA and proteins) and the nucleolus.
• What is the function of the nucleus?


  Controls the cells activities by controlling the transcription of DNA. DNA contains the instructions to make proteins. The pores allow substances to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
• Describe the structure of a lysosome


  A round organelle with no clear internal structure surrounded by a membrane.

  
• What is the function of a lysosome?


  Contains digestive enzymes (kept separate from the cytoplasm by the surrounding membrane) and can be used to digest invading cells or to break down worn out components of the cell.
• Describe the structure of a ribosome 


  A very small organelle that floats free in the cytoplasm or is attached to the Rough endoplasmic reticulum. It is made up of proteins and RNA and is not surrounded by a membrane.

  
• What is the function of the Rough endoplasmic reticulum?

  Folds and processes proteins that have been made at the ribosomes
• What is the function of the Smooth endoplasmic reticulum?

  Synthesises and processes lipids
• Describe the structure of a vesicle

  Fluid filled sac in the cytoplasm surrounded by a membrane

  
• What is the function of vesicles?

  Transports substances in and out of the cell via the plasma membrane and between the organelles. Some are formed by the Golgi apparatus or the endoplasmic reticulum, while others are formed at the cell surface.
• Describe the structure of the Golgi apparatus

  A group of fluid filled, membrane bound, flattened sacs
• What is the function of the Golgi apparatus?


  Processes and packages new proteins and lipids.

  Also makes lysosomes
• Describe the structure of mitochondria

  Double membrane, the inner fold forms cristae.

  Inside the mitochondria is the matrix which contains the enzymes involved in respiration.
• What is the function of Mitochondria?

  Site of aerobic respiration where ATP is produced. They are found in large numbers in cells which are active and require a lot of energy.
• Describe the structure of chloroplasts

  Small flattened structure found in plant cells. It is surroundead by a double membrane and also has membranes inside called thylakoid membranes. These membranes are stacked up in parts of the chloroplast to form Grana. Grana are linked together by lamellae- thin flattened pieces of thylakoid membrane.

  
• What is the function of chloroplasts?

  The site of photosynthesis, some parts of photosynthesis happens in the grana and other parts happens in the stroma (thick fluid found in chloroplasts)
• Describe the structure of Centrioles

  Small, hollow cylinders made of microtubules, found in animal cells but only some plant cells.

  
• What is the function of Centrioles?

  Involved in the separation of chromosomes during cell division
• Describe the structure of Cilia


  Small, hair-like structures found on the surface of membranes of some animal cells.

  In cross section, they have an outer membrane and a ring of nine pairs of protein microtubules inside, with two microtubules in the middle. Known as the 9 + 2 formation.
• What is the function of Cilia?

  The microtubules allow the cilia to move, allowing substances to be moved along the cell surface.
• Describe the structure of Flagellum

  Flagella on eukaryotic cells are like cilia but longer. They stick out from the cell surface and are surrounded by the plasma membrane. Inside there are two microtubules in the centre and nine pairs around the outside.

  
• What is the function of Flagella?

  The microtubules contract to make the flagellum move.
• Describe the structure of the Rough Endoplasmic Reticulum

  Contains a series of connected, flattened membrane bound sacs called cisternae, which are studded with ribosomes.
• Describe the structure of the Smooth Endoplasmic Reticulum

  Series of connected, flattened membrane bound sacs called cisternae.
• Describe the structure of the Cytoskeleton

  A network of fibres in the cytoplasm of all eukaryotic cells.

  The cytoskeleton has three components:

  -Microfilaments

  -Microtubules

  -Intermediate Fibres
• What is the function of the Cytoskeleton?

  Maintain the shape and stability of cells, while holding organelles in place. It also controls cell movement and organelle movement. The cytoskeleton is dynamic which allows it to respond to changes in the cell and carry out its functions.
• What are Microfilaments?

  Contractile fibres formed from actin, they are involved in cell movement and cell contraction during cytokinesis.
• What are Microtubules?

  Tiny protein cylinders.

  They act as tracks for organelle movement. Spindle fibres are Microtubules.
• What are Intermediate Fibres?

  Give mechanical strength to cells and help maintain integrity.
• Protein production

  1. DNA from nucleus copied into mRNA via transcription

  2. mRNA attaches to ribosome on rough endoplasmic reticulum

  3. Ribosome reads mRNA and synthesises protein via translation

  4. Protein passes into lumen of rough endoplasmic reticulum to be folded and processed

  5. Processed proteins transported to Golgi apparatus in vesicles

  6. Golgi apparatus modifies proteins, preparing them for secretion

  7. Modified proteins leave Golgi apparatus in vesicles

  8. Vesicles fuse with cell surface membrane, releasing proteins by exocytosis
• Nucleus


  • Stores DNA that codes for protein production
  • Contains nucleolus that manufactures ribosomes required for protein synthesis
• Cells that produce a large number of proteins

  • Have an extensive rough endoplasmic reticulum
• Proteins that go through the Golgi apparatus are usually exported, put into lysosomes (e.g. hydrolytic enzymes) or delivered to other organelles
• What are the features of a Prokaryotic cell?

  Prokaryotes

  -Very small (less than 2 micrometers)

  -Circular DNA

  -No nucleus, DNA free in cytoplasm

  -Cell wall made of a polysaccharide

  -Few organelles and no membrane bound organelles

  -Small ribosomes - 70s

  -Flagella, made of protein flagellin, arranged in a helix
• What are the features of a eukaryotic cell?

  -Larger cells (10-100 micrometers)

  -DNA is linear

  -Nucleus present

  -No cell wall in animal cells, planT cells have a cell wall made out of cellulose and fungal cells have a cell wall made out of chitin

  -Many membrane bound organelles

  -Flagella made of microtubules proteins in a 9+2 formation

  -Larger ribosomes- 80s
• Draw a diagram of a prokaryotic cell

  Prokaryotic cell