1. Cell Structure Flashcards
What is a eukaryotic cell?
- It has a nucleus.
- They usually have mitochondria.
- In plants cells only they have chloroplasts.
What is a nucleus?
Controls all activities of the cell.
What is cytoplasm?
A liquid gel in which most of the chemical reactions take place.
What is cell membrane?
Controls what passes in and out of the cell.
What are mitochondria?
Structures in the cytoplasm where most of the energy is realeased during respiration.
What are ribosomes?
Where protein synthesis occurs and synthesis for all other proteins in the cell.
What is a cell wall?
Made of cellulose it strengthens the cells and gives it support.
What are chloroplasts?
They absorb energy from the sun to make food by photosynthesis.
What is a permanent vacuole?
A space in the cytoplasm filled with cell sap that keeps the cells rigid to support the plant.
What are specialised cells?
Cells specialised to carry out a particular function.
What are adaptations of root hair cells?
- Root hairs provide large surface area.
- A large permanent vacuole affects movement of water from soil.
- Root hair positioned close to xylem
What is the function of a root hair cell?
Enables plants to take in water and mineral salts.
What are the adaptations of a sperm cell?
It has a middle section full of mitochondria to release energy.
What is the function of a sperm cell?
To fertilise egg cells.
What is the tail on a sperm cell for?
To swim.
What are the adaptations of red blood cells?
- cytoplasm contains haemoglobin to transport oxygen
- no nucleus - can contain more haemoglobin
- biconcave shape to maximise surface area
What is the function of a red blood cell?
To carry oxygen.
What does a red blood cell NOT have?
A nucleus.
What is the function of a nerve cell?
To send nerve impulses around the body.
What is the equation for magnification?
Magnification = size of image (I) / actual size (A)
What are fat cells?
Storage cells. They help animals to survive when food is in short supply.
What are the adaptations of fat cells?
- They have little amounts of cytoplasm - to leave room for large amounts of fat.
- They have very few mitochondria as they use little energy.
- They can expand when it fills up with fat.
What are specialised cells grouped together to form?
A tissue
What joins parts of the body together?
Connective tissue
What does nervous tissue do?
Carries information around the body.
What do photosynthetic cells do?
Make food by photosynthesis
What do storage tissues do?
Store extra food made as starch
What are stem cells?
Unspecialised cells that can change to different types of cells
Where are stem cells found? - animals
Human embryos and adult bone marrow
What can stem cells be used to treat?
Paralysis and diabetes
Where are stem cells found? - plants
Meristems of plants
Advantages of stem cells?
- They can be taken without hurting
- Will provide vital clues about how tissues develop
- Could treat Parkinson’s, Alzheimer’s, heart disease, strokes, arthritis, burns etc
Disadvantages of stem cells?
- Use of embryos is unethical
- Embryonic stem cell research = murder
- Immune system might recognise stem cells as foreign and be rejected and die
What does a nucleus contain?
Chromosomes
How many pairs of chromosomes are in a human nucleus?
23
What does a chromosome contain?
Many genes
What is a gene?
A length of molecule called DNA
What is mitosis?
It’s for growth repair and replacement of cells
What are cancer cells?
Arise due to mutations in genes that control mitosis. Leads to uncontrolled cell division and tumours.
What are the two types of tumours?
Benign and malignant
What are benign tumours?
Unable to spread to other parts of the body and are non-cancerous
What are malignant tumours?
Can invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours.
What is diffusion?
The movement of particles in a gas or a liquid from an area of high concentration to an area of low concentration
What is a partially permeable membrane?
Lets small soluble substances through but not others
What factors affect the rate of diffusion?
- distance
- surface area
- concentration gradient / difference
- temperature
What increases the rate of diffusion?
- decreased distance
- increased surface area
- increased concentration gradient
- increased temperature
What is osmosis?
Diffusion of water molecules from a dilute to a more concentrated solution through a partially permeable membrane down a concentration gradient
What does a partially permeable membrane do?
Allows small water molecules to pass through but not large solute molecules
What happens when a red blood cell is placed in pure water?
Water moves into cell by osmosis and bursts
What happens when a cell is placed in a liquid the same concentration?
No net movement of water by osmosis
What happens when a red blood cell is placed in a concentrated solution?
Water moves out of the cell and shrivels
What does turgid mean?
When water has moved into the cell by osmosis and cell contents is pushed outwards against the wall
What does flaccid mean? And plasmolysed?
When water has moved out of a cell and becomes shrivelled ONLY IN PLANTS CELLS WHEN CONTENTS OF CELL COMES AWAY FROM CELL WALL
What does a dilute solution of sugar contain?
A high concentration of water (solvent) and a low concentration of sugar (solute)
What does a concentrated solution of sugar contain?
A relatively low concentration of water and a high concentration of sugar
What is active transport?
The movement of molecules and ions across a cell membrane against the concentration gradient - to a region of higher concentration
How does active transport go against the concentration gradient?
It uses energy from respiration and a carrier protein
What can be reabsorbed by active transport?
Glucose into the blood from the kidney tubules
Why do plants rely on active transport?
To obtain mineral ions through root hair cells
What do cells involved in active transport have?
Lots of mitochondria because aerobic respiration takes place here and releases energy needed for active transport
What happens to SA to volume ratio when the size of an object increases?
Decreases
What happens to SA to volume ratio when the size of an object decreases?
Increased
Why do multicellular organisms need a transport system?
As size increases SA/V ratio decreases
surface area is no longer big enough to supply needs of the body - needs to be sped up to move materials in and out of the organism
How many micrometers are in a millimetre?
1000
What is a concentration gradient?
The difference in concentration of two solutions.
What is a prokaryotic cell?
- bacterial cell
- no nucleus
- genetic material is a single loop of DNA
Examples of some cells that divide by mitosis
- hair and nail cells
- skin cells
- red and white blood cells
Is a bacterium a prokaryotic or eukaryotic cell?
Prokaryotic
Which cells are smaller? Plant cells or bacterial cells?
Bacterial cells
What substance is the cell wall made of?
Cellulose
