Module 1- Intro To Cells Flashcards
How many cells are there approximately in the human body?
Around 50 million million (50 trillion) cells
What are cells regarded as in biological terms?
The basic unit of life
What can the human body be thought of as?
A large colony of cells
What are the three major areas into which cells are traditionally divided?
- The nucleus
- The cytoplasm
- The plasma membrane
What is the location of DNA in a cell?
Nucleus
The nucleus houses the genetic material of the cell.
What is one of the main functions of the nucleus?
Controls cellular activity
The nucleus regulates various cellular processes and functions.
What separates the nucleus from the cytoplasm?
Nuclear envelope
The nuclear envelope is a double-layered, porous membrane.
True or False: The nuclear envelope is a single-layered membrane.
False
The nuclear envelope is double-layered.
What does DNA stand for?
Deoxyribonucleic acid
What is the primary function of DNA?
Determines the majority of human traits
What are the building blocks of DNA?
Nucleotides
What is the characteristic shape of DNA?
Double helix
How is DNA usually organized in the cell?
Wrapped around histone proteins
True or False: DNA has a single spiral structure.
False
Fill in the blank: DNA is composed of building blocks called _______.
nucleotides
What role do histone proteins play in relation to DNA?
Function like bobbins or spools
What happens to DNA when cells prepare to divide?
The DNA is wound-up very tightly and begins to fold up upon itself
This process is similar to an elastic band being wound up between two pens.
What are chromosomes?
Thread-like structures observed within the nucleus formed from tightly wound DNA
Chromosomes are visible during cell division.
True or False: Chromosomes are only visible in the nucleus when a cell is not dividing.
False
Chromosomes become visible when DNA is tightly wound during cell division.
Fill in the blank: The tightly wound DNA observed during cell division is called _______.
chromosomes
How many pairs of chromosomes do human cells usually have?
23 pairs
This gives a total of 46 chromosomes, known as the diploid number.
What are the first 22 pairs of chromosomes in humans called?
Autosomes
Autosomes appear the same in both sexes.
What are the sex chromosomes in humans?
XX (female) and XY (male)
The 23rd pair consists of these sex chromosomes.
What is a karyograph?
Photographs of chromosomes arranged in pairs according to size
Karyographs are used to determine an individual’s karyotype.
What is a karyotype?
An individual’s chromosomal makeup
Karyotypes are determined using karyographs.
True or False: Spermatozoa and ova are exceptions to the usual number of chromosomes in human cells.
True
Spermatozoa and ova have a haploid number of chromosomes.
Fill in the blank: The diploid number of chromosomes in human cells is _______.
46
What can healthcare professionals determine from a persons karyotype
If the correct (diploid) number of chromosomes are present
If there are missing or extra chromosomes (aneuploidy)
The sex of an individual
If there are extra or missing pieces of chromosomes
What are karyographs most often prepared from
Cells of unborn babies harvested through amniocentesis
What is amniocentesis
When amniotic fluid is collected using a needle
Why do they use amniotic fluid
Since the foetus is suspended in this medium it will contain foetal cells which have detached
What will the cells in the amniotic fluid be in a state of
Active cell division and have visible chromosomes within their nuclei
What is a common disease revealed during amniocentesis
Down syndrome
In 95% of cases how many copies are there of blank chromosome
There are 3 copies of the 21st chromosome- trisomy 21
What does the extra chromosome result in with Down syndrome
Alters the course of development and causes characteristic clinical features
What are the statistics of down syndrome
1/800 live births
What about the mother will affect the likelihood of a child being born with downsyndrome?
Age of the mother
Clinical features of Down syndrome
Single transverse palmar crease (simian line)
Flattened facial features and large gap between the big toe and second toe
Macroglossia (enlargement of the tounge)
Pronounced epicanthal folds around the eyes
Brushfield spots
Septal defects
What can macroglossia lead to
Interfere with swallowing and impaired speech
What are brushfield spots
Observed as pale spots in the iris
What are septal defects
Hole in the heart
They can allow a mixing of the oxygenated blood on the left hand side of the heart and the deoxygenated blood on the right have side
What is patau syndrome
Caused by extra copy of chromosome 13
Usually results in incomplete brain development
Missing eyes
Cleft palate
Occurs approx. 1/10,000 births with most babies dying soon after birth
What is the cytoplasm
Region of a cell between the nuclear envelope and the plasma membrane
What does cytoplasm consist of
System of interconnected flattened membranes called the endoplasmic reticulum (ER)
What are the two types of ER
Rough ER - due to presence of ribosomes is the major site of protein synthesis
Smooth ER - lacks ribosomes and is major site of lipid (fat) synthesis
What is the cytosol
An aqueous solution within the cytoplasm
What makes up cytosol
Complex mixture of water salts sugars amino acids and growth factors
