Eduqas Cell structure and organisation

What is nucleus

• Contains cells DNA- this is the genetic material that is passed on from one generation to the next and provides the code for the synthesis of proteins

What role does the nucleus play in protein synthesis?

The nucleus contains DNA. To begin protein synthesis, a strand of mRNA is made using DNA as a template in a process called transcription.
The mRNA strand leaves the nucleus through a nuclear pore and carries the genetic code to the cytoplasm, where it directs the production of proteins at ribosomes.

Describe the structure of the nucleus and its role in protein synthesis.

The nucleus is enclosed by a double membrane called the nuclear envelope, which contains nuclear pores that allow mRNA to exit into the cytoplasm.

Inside, the nucleoplasm (a fluid similar to cytoplasm) is chromatin, which is the cell’s DNA.
The nucleolus, found within the nucleus, produces ribosomal RNA (rRNA)

What is the function of mitochondria and how are they structurally adapted?

Mitochondria release energy in the form of ATP during aerobic respiration. They have a double membrane, with the inner membrane folded into cristae to increase surface area for ATP synthesis. The inner space is filled with the matrix containing ribosomes and mitochondrial DNA.

What is the significance of mitochondrial DNA?

Mitochondrial DNA allows them to replicate independently and is evidence they were once free-living organisms ingested by ancestors of eukaryotic cells (endosymbiotic theory).

What is the role of the rough ER?

A series of membranes connected to the nucelear membrane, covered in ribosomes. It transports proteins and is the site of translation.

What is the function of the smooth ER?

involved in the synthesis of lipids.

What are ribosomes made of and what is their role?

Ribosomes have large and small subunits They come together around a strand of mRNA, which fits into the mRNA groove.

and are made of protein and rRNA.

What does the Golgi body do in a cell?

It modifies and packages proteins from the rough ER. Proteins enter in vesicles, are modified, and exit at other end of golgi sac, the vesicle containing the modified protein travels to the cell outer plasma membrane where the protein is released by exocytosis. It also forms glycoproteins and lysosomes.

What is the golgi body?

stack of flattened membranous sacs

What are lysosomes and how do they function?

Lysosomes are vesicles containing digestive enzymes.

They can be used to bread down worn out organelles and to digest material taken in by phagocytosis.

They fuse with vacuoles containing material and release their digestive enzymes into the vacuole, the digestive enzymes break down the vacuole

What are centrioles in animal cells?

small cylinders that separate from each other during the early stages of mitosis to form the spindle fibres

Function and structure of chloroplasts

have a double membrane

site of photosynthesis

contain stroma, thylakoids (membrane contain chlorophyll which absorbs light energy used in photosynthesis), grana which are linked by lamellae

What is the significance of chloroplast DNA?

Like mitochondria, chloroplasts have their own DNA and ribosomes, supporting the endosymbiotic theory that they evolved from free-living organisms.

Length of eukaryotes and prokaryotes

Eukaryotes usually 10-100μm
Prokaryotes usually 1-10μm

Difference in ribosomes in eukaryotes and prokaryotes

70s in prokaryotes (50s subunit and 30s subunit)

80s in eukaryotes (60s subunit and 40s subunit)

What are cell walls made out of

Cell walls are made of cellulose in plants, chitin in fungi, and peptidoglycan in bacteria.

What is a virus

• no cytoplasm

• consist of nucleic acid and protein coat

• In most viruses that infect eukaryotes the nucleic acid is RNA, but for bacteria the nucleic acid is DNA

What is the definition of cell theory

New cells are formed from other existing cells, and the cell is a fundamental unit of structure, function, and organisation in all living organisms.

what is the difference in sites of respiration between prokaryotic and eukaryotic cells

Prokaryotic - takes places in cytoplasm and across the cell membrane

Eukaryotic- takes place in mitochondria (glycolysis in cytoplasm, rest in mitochondria).

How is a light microscope calibrated at low and high power?

• Use a stage micrometer and eyepiece graticule

• Align the scales and calculate the value of one graticule unit in µm.

• Repeat for each objective lens (low and high power).

How is a slide of living cells prepared for observation?

• Use a drop of water or appropriate stain (e.g. methylene blue for nuclei).

• Place specimen

• Add coverslip carefully to avoid air bubbles.

What is a tissue

group of cells that have a similar structure and they work together to perform a particular function

Examples of animal tissues and plant tissues

Animal:

• epithelial tissue

• muscle

connective tissue

Plant:

• xylem

• phloem

What are the levels of organisation

• Cell

• Tissue

• Organ

• Organ system

• Organism

Examples of organs in animals and plants

Animal: heart, brain

Plant: root, leaf

What is an organ system

made up of two or more organs working together to perform a life function, such as the respiratory system or digestive system in mammals

What is epithelial tissue

eg ciliated, columnar, and squamous epithelia- epithelial tissue lines the spaces in animals such as the digestive and respiratory system

What is a muscle

eg smooth, striated and cardiac muscle- muscle tissue contracts and relaxes to move parts of the animals

What is connective tissue

eg collage- structural tissue in animals