Chapter 2: The Cell Flashcards
Who developed the cell theory
microbiologists Schleiden and Shwann
What is the cell theory
An explanation of the relationship between cells and living things
What does the cell theory state
- All living things are made of cells
- New cells are created by old cells dividing into 2
- Cells are the basic building block of life
Give the definition of cells
The basic structural and functional unit of all living things
What is the protoplasm and what does it consist of
The colourless material compromising the living part of the cell including the cytoplasm, nucleus and other organelles. The protoplasm is also referred to as living matter so the cell is the smallest unit of protoplasm.
What does the cell consist of
cell nucleus, and the cytoplasm
What is the liquid content in the cell
The ground plasma/ hyaloplasm
What is the cytoplasm
The protoplasm enclosed by the plasma membrane of the cell, excluding the nucleus in eukaryotic cells and cellular DNA in prokaryotic cells
What are the inorganic ingredients in the protoplasm
- Water
- Gases such as oxygen and carbon dioxide dissolved in the ground plasma
- Mineral salts (in ionic form) eg. NaCl and potassium ions
What are the organic ingredients in the protoplasm
- Proteins
- Carbohydrates
- Lipids
- Nucleic acids
Describe what a true solution is and give an example
Homogeneous solutions eg. salts, sugar and gasses dissolved in water
Describe what suspension is and give an example
Heterogeneous solutions eg. the cell organelles floating in the groundplasm
Describe what emulsion is and give an example
The solvent as well as the solute are liquids eg. oil droplets dispersed in water
Describe 5 things about colloidal solutions
The particles of the solute are too big to float but too small to sink. Particles may have similar electrical charges so they repel each other and remain in suspension. Particles form long strands/aggregates.
Proteins form colloidal solutions, in solid form they are gel and in liquid state they are described as sol
In what state is the endoplasm
Sol state
In what state is ectoplasm
Gel state
With what is the state of protoplasm reversible
By changes in pH, temperature and pressure
Describe the appearance of the groundplasm
It is a clear liquid that has a grey appearance due to the organelles and dissolved substances suspended in it
What are the functions of the cytoplasm
- Site of all metabolic processes
- Substances circulate through movement of the cytoplasm (cyclosis)
- Stores substances essential to life
- Helps maintain the shape of the cell
What is the cell wall
The only non living part of the cell and only occurs in plant cells
What does the cell wall consist of
The primary cell wall, the middle lamella and secondary cell wall
Describe 6 aspects of the primary cell wall
All plant cells have one. It is a thin layer outside the cell membrane. It consists of cellulose fibres that stretch as the cell grows. It has small openings called pits. Pits allow lateral transport between cells. Pits contain cytoplasmic threads (plasmodesmata) that extend to adjacent cells. The plasmodesmata facilitate transport between cells
List 3 facts about the middle lamella
Consists of pectin and occurs outside primary cell wall. The cell walls of adjacent plant cells are connected by the middle lamella
Describe 6 aspects of the secondary cell wall
Secondary cell wall develops between the cell membrane and primary cell wall as the cell grows older.
It is inelastic. It consists of thick cellulose fibres with lignin in between.
They can also contain suberin (water proof substance). The pits are deeper and also have plasmodesmata.
Give 2 functions of the cell wall
- Protects the living contents of the plant cell against mechanical injury
- Gives rigidity and support to the plant cell, responsible for cell shape
What is the plasma membrane
The very thin outer living boundary of the cytoplasm
What is another word for the plasma membrane
cell membrane
Comment on the structure of the cell membrane
It is differentially permeable
What does the fluid mosaic theory state
- The cell membrane consists of a double layer of phospholipid molecules with large protein molecules imbedded in the layer of phospholipids
- Some proteins extend through the 2 phospholipid layers or occur on the outside
- Each phospholipid contains a head and a tail.
Describe the head and tale of a phospholipid
The head is a phosphate group, faces outwards and is hydrophilic
The tail is two fatty acids, faces inwards and is hydrophobic
Why is the cell membrane not static
The phospholipids and proteins in it can move around
What is the double layer of phospholipids in the cell membrane impermeable to
Water soluble molecules like glucose, amino acids, salts and nucleic acids
How do water soluble molecules move through the hydrophobic double layer of the cell membrane
By means of carrier proteins that pick up the molecules on one side and release them on the other side. They take substances through the cell membrane against the concentration gradient. This is active transport
What are the ways proteins can be associated with membranes
Proteins can be permanently inserted into the membrane (integral proteins)
They can extend throughout the membrane (transmembrane proteins)
Other membrane proteins are anchored in the membrane but go through only one side of it. Others are not anchored through the membrane at all but are associated with the membrane by ionic interactions. (peripheral proteins)
What are the functions of the cell membrane
- Encloses the cell contents
- Selectively/ differentially permeable and controls the movement of substances in and out the cell
- Important part of cellular immunity system
- Membrane inside the cell is important for bringing parts of the cell in contact with one another eg. ER
Fill in the missing word:
Substances such as ______ continuously move in and out of the cell
water, gasses, dissolved salts and amino acids and glucose
What processes are responsible for the movement of substances moving in and out of the cell
Diffusion, Osmosis, Active transport
Describe diffusion within cells
It takes place because of the kinetic energy of each particle. Because of diffusion dissolved substances can spread evenly through the groundplasm. Substances can also diffuse from cell to cell
What is the definition of diffusion
The spontaneous movement of molecules of a liquid or gas from an area of high concentration to a low concentration until equilibrium is reached
What can the rate of diffusion be influenced by
- The concentration gradient. (The greater the differences in concentration the faster diffusion occurs)
- The temperature. (High temperature promotes diffusion)
- Pressure. (When pressure increases the rate of diffusion increases)
Give the definition of osmosis
The movement of water molecules from an area of a high water potential to a low water potential through a selectively permeable membrane until equilibrium is reached.
Give the definition of water potential
The ability of a solution to release water given its large number of free water molecules
Which particles move during osmosis
water molecules
What kind of membrane does osmosis take place in
A selectively permeable membrane
What is a hypertonic solution
A solution with a greater concentration of solutes than another solution
What is a hypotonic solution
A solution that has a lower concentration of solutes than another solution
What is an isotonic solution
When a solution’s effective osmole concentration is the same as that of another solution
Why are diffusion and osmosis passive processes
No energy is required for the types of transport
What is the concentration gradient
The difference between the high concentration of molecules in one area and the low concentration of the same molecules in another area
What is passive transport
The movement of molecules down a concentration gradient from a high to low concentration
Ordinary and facilitated diffusion of ions and molecules. It occurs with the ion and concentration gradient on either side of the membrane
What is active transport
When particles move from a low to a high concentration through membranes and against the concentration gradient on either side of the membrane. Energy is needed for the process. Most membranes have carrier molecules for this process
Explain what happens during exocytosis
The membrane of a transport vesicle fuses with the cell membrane and the contents of the transport vesicle are dumped outside the cell.
The process is used to secrete proteins and carbohydrates from the cell
Explain what happens during endocytosis
Cells form pseudopodia that flow around macromolecules (or foreign objects such as bacteria, viruses and toxins) and fuse to form vesicles with the macromolecules as their contents.
These vesicles fuse with lysosomes in the cells which then process the vesicle content.
What is the difference between endosmosis and exosmsosis
Endosmosis: the inflow of solvent (water) into a cell from outside when a cell is placed in distilled water and the cell swells up
Exosmosis: the outward flow of water from the cell when placed in a more concentrated solution like sugar solution (hypertonic) and the cell shrinks
What is the nucleus
A prominent, round or oval shaped structure in the cytoplasm
Where is the nucleus found in plant cells and in animal cells
In animal cells it is usually in the centre of the cell but not in plant cells because it is usually displaced by a large vacuole
What does the nucleus consist of
The nuclear membrane, the nucleoplasm, nucleolus and the chromatin network
What is the nuclear membrane
A double differentially permeable membrane that contains small pores and encloses the nucleus
What is the ER in full words
Endoplasmic reticulum
What do the pores in the nucleus do
They control the passage of substances in and out of the cell allowing the nuclear contents to be in direct contact with the groundplasm
What is the space between the two membranes in the nucleus called
perinuclear space
What is the nucleus filled with
a jelly like fluid called the nucleoplasm
What is the nucleolus
A dark body that consist of RNA and proteins and is visible in the nucleoplasm
What is the chromatin network and what happens to it when the cell divides
Tangled threads that occur throughout the nucleoplasm and it condenses to form chromosomes when the cell divides
What does the chromatin network consist of
the macromolecule DNA
What is the purpose of chromosomes
They bear hereditary factors known as genes
What is the difference between a eukaryote and a prokaryote
Eukaryotes are organisms with cells that have true nuclei. Their DNA is enclosed by a nuclear membrane and is inside the nucleus.
Prokaryotes are organisms with cells that do not have true nuclei. Their DNA is not enclosed by a nuclear membrane and occurs freely in the cytoplasm
How many chromosomes do cells consist of, what is the exception and how many cells does it consist of
Each cell in the human body consists of 46 chromosomes. Egg cells and sperm cells have 23 chromosomes each
What are the functions of the nucleus
- Controls the cells metabolism
- Differentiation and specialisation
- The chromosomes carry hereditary characteristics from cell to cell
- Reproduction of cells/organisms
What is the single form of mitochondria and where is it found
Mitochondrion, they are dispersed throughout the cytoplasm of plant and animal cells
What shape do mitochondria have
They are cylindrically shaped hollow rods
Describe the outer membrane and the inner membrane of mitochondria
The outer membrane is smooth and the inner membrane contains finger like folds known as cristae
What does the cristae in mitochondria do
It increases the inner surface area of the mitochondrion where chemical reactions take place
What is the semi fluid substance that fills mitochondria and what does it consist of
the matrix, it contains ribosomes and enzymes
What do ribosomes do in mitochondria
The ribosomes synthesize the enzymes that are necessary for chemical reactions to take place inside the mitochondrion
What is the definition of cellular respiration
The gradual release of energy from an energy rich fuel molecule (glucose) in the presence of oxygen with water and carbon dioxide as waste products.
Where is the energy produced during cellular respiration stored
The energy is temporarily stored in the energy carrier of the cell (ATP) and is available for work in the cell when necessary
Why is the mitochondria called the powerhouse of the cell
Due to the large amounts of energy released during cellular respiration
What is the chemical formula for cellular respiration
(check in notes)
What DNA does the mitochondria contain and how is it transferred? What can this DNA be used for
mtDNA, it is transferred from mother via the egg cell to the next generation. It can be used to study the genetic history of a person on the maternal side and connect someone to a crime
What is ATP written in full
Adenosine triphosphate
What is the function of mitochondria
Cellular respiration takes place in the mitochondria
During cellular respiration energy is released from carbohydrates eg. glucose in the presence of oxygen
The energy released forms part of the compound ATP
What are ribosomes and what do they consist of
They are small spherical structures that occur in plant and animal cells. They consist of RNA and proteins
Where do ribosomes occur
In the ER, in mitochondria, chloroplasts and in groups of the cytoplasm (known as polyribosomes)
What is the function of ribosomes
Ribosomes are the site of protein synthesis
Explain what ER is, where its found, what it forms and what it is connected to
ER is a fine membranous network found in plant and animal cells. It forms a continuous system of canals throughout the cytoplasm. It is connected to the cell membrane and the nuclear membrane
What are the two types of ER
Rough/granular/course ER and
Smooth/agranular ER
Explain the types of ER
Rough ER has ribosomes on its surface. It is continuous with the outer layer of the nuclear membrane. It works with the Golgi apparatus to transport newly formed proteins to the where they are needed in the cell.
Smooth ER has no ribosomes on its surface. This network expands the surface area for metabolic activities and the storage of important enzymes and their products.
What are the functions of the ER
- The ER transports substances from one part of the cytoplasm to another (internal transport system)
- It increases the internal surface area of the cell
- Brings the cell contents in contact with the extracellular environment
- Serves as basis for attachment for the ribosomes and plays a role in protein synthesis
What is the Golgi apparatus/ Golgi complex
An organelle found in all eukaryotic cells
What does the Golgi complex consist of
dictyosomes (stacks of hollow flat membrane sacs)
Where does the Golgi complex occur and which cells is it abundant in
It occurs in plant and animal cells near the nucleus and is abundant in cells that have a secretory function
What are the functions of Golgi apparatus
- Plays a role in producing and processing secretions such as mucus and saliva
- Plays a role in forming other membrane systems
- Plays a role in the formation of lysosomes
- Processes, changes and sorts proteins
Where do plastids occur
only in plant cells
What is stored and manufactured in plastids
Important chemical components for cellular use
What do plastids contain and what does that do
Pigments used in photosynthesis and the type of pigment present can change/ determine the colour of the cell
What are the types of plastids
Chloroplasts, chromoplasts, and leucoplasts
What are chloroplasts and where do they occur
They are oval shaped plastids which mainly occur in the photosynthesising parts of the plant like the leaves
What kind of membrane do chloroplasts have
A chloroplast is surrounded by a double membrane (inner and outer membrane)
What fluid is chloroplast filled with
a fluid matrix known as the stroma
What are lamellae
Disc shaped membranes in the stroma
What are the thickenings that occur on the lamellae called
Thylakoids
What are the 4 functional units of the Golgi
the cis-Golgi, medial-Golgi, endo-Golgi, and the trans-Golgi regions
What occurs in the Golgi
The cis-Golgi region receives protein or lipid filled vesicles from the ER which are transported to the trans-Golgi region where it is packed and leaves the Golgi apparatus. It is then transferred to other localities in the cell for further metabolic reactions
What are the small stacks formed by the lamellae called, in singular and in plural form
grana in plural form and granum in singular
Where is the chlorophyll imbedded
In the lamellae
What are the grana in chloroplasts connected by
A membrane known as the intergranum
What does the stroma contain and what does it do
It contains enzymes that control photosynthesis as well as starch grains, oil droplets and ribosomes
What are the most important pigments in chloroplast
The green chlorophyll and the carotenoids (the yellow, orange and red pigments)
What do the pigments in chloroplast do
They absorb light for photosynthesis and give colour to plant structures
What are the 4 functions of chloroplasts
- Photosynthesis occurs in chloroplasts
- During photosynthesis energy rich carbohydrates (glucose) are built up in the chlorophyll containing parts of the cell
- The green chlorophyll absorbs energy from the sun
- Water and carbon dioxide are required. Oxygen is released as a by-product
Give the definition of photosynthesis
The building up of carbohydrates (glucose) from carbon dioxide and water using radiant energy from the sun that is trapped by chlorophyll. Oxygen is released as a by-product
Give the chemical formula for photosynthesis
(check in notes)
What are chromoplasts and what pigment do they contain
They are plastids that occur in yellow, orange and red flowers, leaves and fruit. They contain pigments known as carotenoids
What happens between chloroplasts and chromoplasts when fruit ripens
Chloroplasts change into chromoplasts when fruit ripens , or when autumn leaves change colour
What are leucoplasts
Colourless plastids that mainly occur in cells that store food in an insoluble form
What are the functions of leucoplasts
- Leucoplasts become specialised to store food in the form of starch, lipids or proteins
- Leucoplasts that store starch are amyloplasts
What are vacuoles
Fluid filled compartments in the cytoplasm
What is the function of chromoplasts
Chromoplasts give the yellow, orange and red colour to flowers, leaves and fruit
What are vacuoles enclosed by
A selectively permeable membrane (the tonoplast)
What is the fluid that fills vacuoles and what does it consist of
Cell sap, it consists of water and dissolved substances
How do vacuoles look in plant and animal cells
In plant cells, vacuoles are large and prominent
In animal cells vacuoles are small or absent
What are the functions of the vacuole in a cell
- Cell sap in the vacuole causes turgor pressure that gives the plant cell rigidity
- Cell sap often contains pigments known as anthocyanins which give blue, violet or purple colour to flowers and leaves
- Storage off dissolved substances such as sugars/salts
- To promote osmosis by creating a low water potential inside the plant cell
Where are contractile vacuoles found, what do they do and what does the name refer to
They are found in unicellular animals and play a role in osmoregulation (regulating the cells water balance).
The name refers to the ability to contract rhythmically in order to move the surface of the cell to get rid of water.
Where are phagosomes/food vacuoles found, what do they do, with what do they fuse and what occurs when this fusion takes place
They are found in small unicellular organisms (amoeba) and play a role in the digestion and storage of food.
They fuse with the lysosomes and digestion of the food vacuole’s contents takes place
What are vesicles
Small vacuoles that transport substances from the Golgi body to other parts inside and outside the cell
What are lysosomes, where do they occur and what is their role
Small vacuoles that are filled with hydrolytic/ digestive enzymes, they occur only in animal cells and they protect the cell against foreign substances or structures and play a role in intracellular digestion
(Lysosomes fuse with food vacuoles and release the enzymes that digest the food or foreign particles)
Why do lysosomes not have typical membrane structures
The membrane of a lysosome is resistant to digestive enzymes
What are the differences between plant and animal cells
Plant cells
- Cell wall present
- Plastids present
- Large vacuole present
- Lysosomes absent
- Centrosomes absent
- Fixed shape
Animal cells
- Cell wall absent
- Plastids absent
- Vacuole small or absent
- Lysosomes present
- Centrosomes present
- Irregular shape
What is the centrosome
The centromere is an area in the cytoplasm near the nucleus of an animal cell
What is in the centrosome
Two small cylindrical shaped structures known as centrioles
At what angle do the centrioles in the centrosome lie
The two centrioles lie close to each other at an angle of 90 degrees
What does each centriole in the centrosome consist of
Each centriole consists of a number of fibrils, each which contain 3 tubular structures known as mictrotubules
What is the function of the centrosome
In animal cells, the centrioles play a role in the formation of the spindle fibres during mitosis
When is a cell turgid or flaccid
When a vacuole is filled to its maximum (turgid)
When it loses a large amount of water (flaccid)
What kinds of vacuoles can be found in animal cells
Contractile vacuoles, phagosomes/ food vacuoles, vesicles and lysosomes
