The Cell

Question 1

What is a cell?

Answer 1

Smallest unit in our body (cells make up tissues and without cells we wouldn’t exist)

Question 2

What is an organelle?

Answer 2

Little organs within the cell

Question 3

What does the nucleus consist of and the function of it?

Answer 3

Nucleus is the largest organelle in the cell
Stores DNA - the genome
Storage, packaging and processing of DNA is the main aspect of the nucleus
Nuclear envelope- ensures contents of nucleus are contained and protected from cytoplasm
Nucleolus- the site for transcription and ribosome production
Nuclear pores- allow movement of mRNA in and out of nucleus (transport out of nucleus occurs through nuclear pores)

Question 4

The genome is stored both in the nucleus and in the mitochondria. It is over 3 billion base pairs. How does it all fit?

Answer 4

DNA is packaged into chromosomes. (23 pairs of) chromosomes are coiled and they are uncoiled for transcription and translation

Question 5

What is transcription (simple sentence)?

Answer 5

Transcription is the process by which mRNA is produced from DNA.
1) Chromosomes are uncoiled to forgive pre-mRNA
2) Introns are removed by splicing and exons are expressed (exons become part of the protein itself - they become part of the amino acids)

Question 6

What ribosomes consist of and function of it?

Answer 6

Ribosomes are the site of protein synthesis
Key structures:
Proteins and ribosomal RNA
2 subunits that fit together - (smaller) mRNA binding site and (larger) tRNA docking site
Ribosomes can be found either free or membrane bound in a cell
Ribosomes are not protected by a membranous layer

Question 7

Ribosomal activity?

Answer 7

Starts protein production via translation
Take 3 bases from DNA - these are codons
Each codon codes for an amino acid

Question 8

What does the Rough Endoplasmic Reticulum (RER) consist of and the function of RER?

Answer 8

RER is abundant in secreting cells
RER is involved in protein synthesis
Protein manufacture
Protein folding (into alpha helices and beta pleated sheets)
Ensures proteins are enclosed in vesicles for transport to Golgi apparatus

RER consists of:
Cisterns - sacs filled with fluid
Surface of RER is studded with ribosomes

Question 9

What does the Smooth Endoplasmic Reticulum (SER) consist of and what is the function of SER?

Answer 9

(SER is attached to RER)

SER consists of:
Tubules (small tubes)
Enzymes embedded in membrane
NO RIBOSOMES

SER produces cholesterol, steroid hormones and phospholipids
SER breaks down lipids, drugs and glycogen
SER stores calcium ions
(Specialised version - sarcoplasmic reticulum)

Question 10

What does Golgi Apparatus consist of and the function of it?

Answer 10

Golgi consists of stacked and flattened membranous sac.
Recieves lipids, proteins and hormone- containing vesicles from endoplasmic reticulum
Adds, alters or removes sugar/ phosphate groups
Golgi is given localisation information

Question 11

Name 2 digestive organelles

Answer 11

Lysosomes, peroxisomes

Question 12

Name 2 digestive organelles

Answer 12

Lysosomes, peroxisomes

Question 13

What do lysosomes consist of and function of lysosome?

Answer 13

(Lysosomes work best in acidic conditions therefore has lots of H+ pumps)
Carries digestive enzymes which are involved in:
autophagy
metabolic functions (e.g. alcohol digestion)
Digest contents taken in by cell by endocytosis

Lots of H+ pumps in membrane
(lots of lysosomes found in phagocytes)

Question 14

What do peroxisomes consist of and function of peroxisome ?

Answer 14

Key structures:
Spherical membranous sacks
Phospholipid bilayer
High concentration of enzymes in the crystalline core

Peroxisomes carry enzymes for detoxification:
Oxidase breaks down alcohol, free radicals and formaldehyde
Catalase breaks down hydrogen peroxide

Question 15

What does the mitochondria consist of and function of it?

Answer 15

(Powerhouse of cell) Largely involved in the production of ATP
Key structures:
Two membranes - smooth outer and cristae in inner membrane to increase surface area (for lots of enzymes to create ATP)
Space in the matrix
Own circular DNA (largely involved in producing tRNA and proteins that are involved in energy production) - maternal lineage

Question 16

Why are diseases/complications in mitochondria very rare in human beings?

Answer 16

Because you wouldn’t be able to produce ATP and you’d die

Question 17

What does the cell (plasma) membrane consist of and function of it?

Answer 17

Keep substances where it needs to be (does this through a phospholipid bilayer). But we also need substances to leave, so there are transmembrane proteins

Key structures:
Phospholipid bilayer
Transmembrane proteins
Carbohydrates
Cholesterol

Question 18

Why are transmembrane proteins important?

Answer 18

Vital for cell communication, and transportation and communication between cells

Question 19

What’s the cells main job?

Answer 19

To interact with other cells (as tissues) or to circulate around the blood

Question 20

What does the cytoplasm consist of and the function of it?

Answer 20

Cytoplasm is the cell forming material. Ensures organelles are not all floating around
Cytoplasm contains cytosol
(Specific composition of the cytoplasm is dependent on cell type)

Question 21

What does the cytoskeleton consist of and the function of it?

Answer 21

Provides structure and generates movement
Cytoskeleton is found in the cytosol
No membrane (cytoskeleton aren’t really organelles)

Key components:
Microfilaments
Intermediate filaments
Microtubules

Question 22

What is the structure and function of microfilaments?

Answer 22

Microfilaments change the cell shape via pushing and pulling the cell membrane
Can break down and reform in different locations

Structure:
Thinnest cytoskeleton component
Contains actin (subunit which makes up microfilaments)

Lots of microfilaments found in muscle cells (as that is where most movement occurs)

Question 23

What is the structure and function of intermediate filaments?

Answer 23

Intermediate filaments are most stable and permanent (they don’t really change shape much, but sometimes they do)

Structure:
‘Internal cables’
Rope-like structure
Twisted tetramer fibrils

Question 24

What is the structure and function of microtubules?

Answer 24

They determine overall cell shape
Involved in organelle distribution
Microtubules always undergo disassembly and reassembly
Act as a pathway for motor proteins

Structure:
Largest part of cytoskeleton
Start at the centrosome
Contain tublin

Question 25

What do we know about centrioles?

Answer 25

Structure:
Short lengths of microtubules
Open ended cylinder

Can be called basal bodies - as they’re present in the basal region of the cilia and flagella

Full function and mechanism of action is unknown

Question 26

Describe the type of cell-to-cell junctions

Answer 26

Gap junctions: allows exchange of ions, second messengers and small metabolites between adjacent cells
Adherens junctions: enables cell-to-cell adhesion (initialisation and stabilisation), regulates the cytoskeleon, and is involved in intracellular signalling
Tight junctions: fence-prevents intramembrane diffusion. Gate- regulates passage of ions, small molecules and water through the paracellular pathway