Cells

Question 1

What is a cell?

Answer 1

Basic unit of life
Vary in size, shape and body functions

Question 2

What is a cell membrane?

Answer 2

Contains a phospholipid bilayer
Establishes cell boundary
Transports oxygen, electrolytes, water and hormones into the cell
Transports waste products out of the cell (CO2)

Question 3

What is a nucleus?

Answer 3

Command center
Sends instructions for cell growth, division and death
Houses DNA
Made up of multiple simpler molecules

Question 4

What is a chromatin?

Answer 4

Housed in the nucleus
Structure made up of DNA double helix packed around proteins
Condenses during cell division to become chromosomes

Question 5

What is a chromosome?

Answer 5

Single strand grouping of condensed chromatin

Question 6

What is the typical structure of human chromosomes?

Answer 6

23 pairs of chromosomes - 46 in total
22 pairs are homologous (look alike) and autosomes (carry genes to determine body traits)
1 pair carries sex chromosome
XX - female
XY - male

Question 7

What is a gene?

Answer 7

Basic unit of heredity
Carries DNA
Each person has 2 copies of each gene (1 from each parent)
DNA in the gene provides instructions on making proteins

Question 8

What is an allele?

Answer 8

Different forms of the same genes e.g. brown, blue, green eye colour

Question 9

What is a dominant allele?

Answer 9

Expressed over a recessive allele

Question 10

What is a recessive allele?

Answer 10

Only expressed in the absence of a dominant allele

Question 11

What is a codominant allele?

Answer 11

Allows expression for both alleles e.g. AB blood type

Question 12

What are some single gene and chromosome gene disorders?

Answer 12

Single - Huntington’s Disease, Cystic Fibrosis
Chromosome - Down’s, Turner’s Syndrome

Question 13

What is the basic process of fertilisation?

Answer 13

Spermatozoom (male gamete) and an ovum (female gamete) join together to form a single cell (zygote)
Takes place in the Fallopian Tube

Question 14

What are the three stages of fertilisation development?

Answer 14

1. Preembryonic period
2. Embryonic period
3. Foetal period

Question 15

What happens in the preembryonic period?

Answer 15

From fertilisation to two weeks
Zygote undergoes cleavage (series of rapid mitotic divisions)
Zygote becomes a blastocyst

Question 16

What happens in the embryonic period?

Answer 16

3-10 weeks
Major systems and structures develop
Called an embryo

Question 17

What happens in the foetal period?

Answer 17

8 weeks until birth
Body structures continue to develop

Question 18

What is a neuron?

Answer 18

Specialised cell
Human brain has approx 86 billion neurons

Question 19

What is the structure of a neuron?

Answer 19

Cell body
Nerve fibres
Dendrites (short fibres from cell body)
Axon (long thin projection)
Myelin sheath (fatty material)
Nodes of Ranvier (gaps in sheath)

Question 20

What are the different types of neurons? x3

Answer 20

1. Sensory
2. Motor
3. Interneurons