Cells (4)

Question 1

How are cells formed?

Answer 1

> Human body develops from single cell calles zygote, resulting from joining of ovum and sperm
Cell division follows (mostly in first 12 weeks) and cell specialisation as foetus grows- these cells hav the same genetic makeup as the zygote

Question 2

What is a cell?

Answer 2

> Building blocks of the body
Over 200 types in the body
Most are microscopic (10-30um diameter)

Question 3

What is the largest cell?

Answer 3

Ovum

500um and just visible to naked eye

Question 4

What is the smallest cell?

Answer 4

Erythrocyte

7.5um

Question 5

What is the longest cell?

Answer 5

Neurone

Up to 1m in length but microscopically thin- longest is sciatic nerve

Question 6

What cells connect body parts?

Answer 6

Fibroplasts

Question 7

What cells form linings?

Answer 7

Erythrocytes

Question 8

What cells transport gases?

Answer 8

Erythrocytes

Question 9

What cells move organs and body parts?

Answer 9

Skeletal muscle cells and smooth muscle cells

Question 10

What cells gather information and control body functions?

Answer 10

Nerve cell

Question 11

What cells store nutrients?

Answer 11

Fat cells

Question 12

What cells fight disease?

Answer 12

Macrophages

Question 13

What cells are involved in reproduction?

Answer 13

Ovum and sperm

Question 14

What is cell theory?

Answer 14

> The cell is the basic structural and functional unit of life
Activity of an organism depends on individual and collective activity of its cells
Biochemical and metabolic activities of cells are dictated by its subcellular structure
Continuity of life has a cellular basis

Question 15

What elements are all cells composed of?

Answer 15

Carbon, hydrogen, nitrogen and oxygen

Have trace amounts of other elements

Question 16

What are the 5 parts of a generalised cell?

Answer 16

1) Plasma cell membrane- Outer boundary of the cell, separates intracellular and extracellular environments
2) Cytoplasm- Material between the cell membrane and the nucleus
3) Organelles- Structures that have intracellular roles, contributing to homeostasis
4) Inclusions- Secretory and storage chemicals of cells ]
5) Nucleus- Contains nucleoplasm and material containing genes. Gened composed of deoxyribonucleic acid

Question 17

What is the plasma membrane?

Answer 17

> Separate intracellular and extracellular environments
Provides a selective barrier, controlling passage of substances in and out of the cell
Composed of 2 layers of phospholipids (bilayer) with proteins embedded in them
Phospholipids have hydrophillic head and hydrophobic tail
Arranged so tails face inwards and heads face outwards

Question 18

What are plasma membrane proteins?

Answer 18

> Some form channels for transport e.g. of electrolytes
Some are markers which is important in cell recognition e.g. blood groups
Some are receptor sites or targets for hormones
Some are enzymes and control chemical reactions
*diagram in lecture notes

Question 19

What is cytoplasm?

Answer 19

> The material between the plasma membrane and the nucleus

> Site of most cellular activities

Question 20

What are the mitochondria?

Answer 20

> “The powerhouse of the cell”
Membranous and sausage shaped
They provide 78% of a cells ATP which is generated through aerobic respiration (the energy making process involving the breakdown of fuel chemicals in the prescence of oxygen)
The more active the cell= the more mitochondria it contains
Cells with the most mitochondria= sperm, muscle and liver.

Question 21

What are ribosomes?

Answer 21

> Granules composed of RNA and protein
Synthesise proteins (including enzymes) from amino acids, using RNA as the template
Found in cytoplasm, on outer surface of nuclear envelope and RER.

Question 22

What is endoplasmic reticulum?

Answer 22

> Series of interconnecting channels in the cytoplasm that form folded membranes
2 types- rough and smooth

Question 23

What is SER?

Answer 23

> Synthesises lipids and steroid hormones and is associated with detoxification of some drugs

Question 24

What is RER?

Answer 24

> Studded with ribosomes which is the site of protein synthesis

Question 25

What is the golgi apparatus?

Answer 25

> Stacked and flattened membranous sacs
Proteins move from RER to GA where they are modified and packaged into vesicles which are stored and then when needed are transported to the surface of the plasma cell membrane where it fuses with it and releases its contents by exocytosis.

Question 26

What are lysosomes?

Answer 26

> Hollow sacs that contain powerful enzymes which can break down fragments of organelles and large molecules e.g. DNA, carbohydrates, proteins, etc into smaller particles which are either recycled or exported from the cell as waste material
Large and abundant in phagocytes

Question 27

What are the centrioles?

Answer 27

> Small and barrel-shaped
Located in the centrosome, near the nucleus
Found in pairs
Pinwheel array of 9 triplets of microtubules
Organise spindal during mitosis
Form the bases of cilia and flagella

Question 28

What is cilia?

Answer 28

> Whip-like, motile extensions on the exposed surfaces of certain cells
Move substances in one direction across the surface of cells

Question 29

What is the nucleus?

Answer 29

> “Control centre”
Largest organelle
Contains nuclear envelope, nucleoli and chromatin
Contains genes (genetic library with blueprints for nearly all proteins)
In a non-dividing cell, DNA is present as chromatin but when the cell prepares itself to start dividing, the chromatin turns into chromosomes
RNA is also found in the nucleus (involved in protein synthesis)
Nucleolus within the nucleus is involved in synthesis and assembly of the components of ribosomes