GCSE Biology - Cells and cell transport

Nucleus

Organelle that contains DNA; controls the cells activities.

Mitochondrion/a

Organelles where aerobic respiration occurs; they’re very small and can’t be seen easily with a light microscope.

Ribosome

Site of second stage of protein synthesis a.k.a. translation

Cell wall

Supports and allows the cell to kepp its shape; made of tough cellulose

Cell membrane

Separates the contents of the cell and the surroundings; controls the movement of substances - such as oxygen or glucose - in and out of the cell.

Large vacuole

Space in the cytoplasm full of cell sap; it is membrane bound, allowing it to support the plant by keeping it rigid.

Chloroplasts

Where photosynthesis takes place; contains chlorophyll - green pigment which absorbs light energy for photosynthesis.

Cytoplasm

Where the chemical reactions needed to carry out life processes take place; contains organelles

Nuclear membrane

The membrane of the nucleus;allows molecules to enter and exit; allows messenger RNA to exit in protein synthesis

Steps for using a microscope and slide preparation

1. Place a thin(thin enough to let light pass through) specimen in the middle of a microscope slide

2. Add a few drops of stain, like iodine solution, so it moves under and stains the sample

3. Place coverslip on top of specimen to keep it flat in place and prevent air bubbles going in

4. Place slide on microscope stage

5. Put x4 objective lens into place

6. Focus with the coarse focussing wheel until sample is in focus

7. Bring the sample into sharp focus with the fine focussing wheel

8. Change to x10 objective lens

9. Bring into focus only using the fine focussing wheel

10. Change to x40 onjective lens if needed

11. Bring into sharp focus only using fine focussing wheel

Prokaryote

A prokaryote does not have nucleus and they have a more simple structure.

Eukaryote

A eukaryote does have a nucleus and has a more complex structure

Flagella

Rotate or move in a whip-like motion to move the bacteria

Plasmids

Small, closed circles of DNA; they can move from one bacterium to another

Genetic material

DNA is found loose in the cytoplasm and not in the nucleus in bacteria.

Cell wall - bacteria

In DNA and bacteria, the cell wall is made of peptidoglycan.

Magnification

The degree to which the size of an image is larger than the image itself

Resolution

The degree to which it is possible to distinguish between two objects that are very close together

Formula for magnification

magnification = image / actual

Palisade mesophyll cell - adaptions

• plant cell

• found in the leaf of a plant

• many chloroplasts to absorb light

• large surface area to absorb more light

Palisade mesophyll cell - functions

• chlorophyll to absorb sunlight to carry out photosynthesis and produce glucose

• CO2 + H2O —> glucose + oxygen

Root hair cell - adaptions

• plant cell

• found in the rot of a plant

• large surface area with side extension

• many mitochondria for aerobic respiration to release energy

• has a thin cell wall

Root hair cell - functions

• absorbs mineral ions by active transport

• absorbs lots of water by osmosis

Guard cells - adaptions

• plant cell

• found in the underside of a leaf

• when cells swell, stomata is open - mostly during daytime

• when cells shrink, stomata is closed - mostly at night

• inner cell wall is thicker than outer cell wall

Guard cells - functions

• allow opening and closing of stomata

• allows entry of CO2 for photosynthesis

• allows exit of O2 and H2O as products of photosynthesis

Sperm cell - adaptations

• animal cell

• produced in the testes of males

• tail allows cell to swim towards the ovum

• many mitochondria for aerobic respiration to release energy for swimming

• acrosomes - digestive enzymes - in the head

• half the number of chromosomes - has 23 and is a haploid

Sperm cell - functions

• can swim to find an egg and fertilise it

• carries the father’s genetic material as it is a male gamete

Ovum - adaptions

• animal cell

• larger than the sperm cell

• contains half the number of human chromosomes - 23 and is a haploid

• has a large store of nutrients

Ovum - functions

• female gamete

• carries the mother’s genetic material for fertilisation

Red blood cell - adaptions

• animal cell

• type of red blood cell

• contains the protein haemoglobin that binds oxygen gas

• biconcave shape to increase its surface area to absorb more oxygen

• no nucleus, leaving more space for the haemoglobin

• flexible so that it can easily travel through capillaries

Red blood cell - functions

• carries oxygen from the lungs to the cells in the body

B lymphocyte - adaption

• developed in the bone marrow

• found in the blood and is a type of white blood cell

• produces antibodies(protein) in response to infections

• many ribosomes to produce all the protein

• many mitochondria for aerobic respiration to release energy used to produce the protein

• animal cell

B lymphocyte - functions

• produces antibodies to fight infections

Ciliated epethelial cell - adaptions

• many extensions of the cell surface membrane, called cilia

• many mitochondria for aerobic respiration to release energy

• animal cell

Ciliated epithelial cell - functions

• found in the trachea and fallopian tube

• cilia waft mucus with trapped dust and bacteria back up the throat to be swallowed

• waft ova through the fallopian tube to the uterus

Phagocyte - adaptions

• found in the blood - a type of white blood cell

• contains many digestive enzymes

• the nucleus is lobed which allows flexibility

• animal cell

Phagocyte - functions

• engulf pathogen and breaks them down using digestive enzymes

Diffusion

The movement of molecules from a region of high to low concentration, where molecules move down the concentration gradient through a partially permeable membrane. It is a passive process and doesn’t require energy.

Examples of molecules moving in and out of cells by diffusion

Animal cells - into: oxygen, glucose, amino acids, fatty acids, mineral ions

Animalcells - out of: carbon dioxide, urea

Plant cells: oxygen, carbon dioxide, amino acids, glucose

Active transport

The movement of molecules from a low to high concentration through a partially permeable membrane. It is an active process and requires energy(ATP). The molecules move through specific protein channels in the cell membrane.

Examples of molecules/ions moving by active transport into cells

Animal cells: reabsorption of glucose and amino acids in the kidneys

Plant cells: mineral ions into root hair cells

Solute

Any molecules that are dissolved in water such as salt or sugar

Semipermeable membrane

A barrier that allows water molecules to pass across, but not solute molecules

Hypertonic

A solution that has more solute

Hypotonic

Solution that has less solute

Isotonic

Solutions that have the same concentration of solute

Solute concentration

A percentage showing the amount of solute dissolved in the water.

For example, higher solute concentration is hypertonic.

Equilibrium

When the concentration of solute and water is the same on both sides of a membrane

Osmosis

The net movement of water molecules from a high to low concentration through a partially permeable membrane. Tiny gaps in the cell membranes of cells allow small molecules like water to pass through but stop larger molecules like salt or sugar.

Electron microscope

• higher magnification and resolution compared to a light microscope

• can only view dead things

Light microscope

• can view living organisms

Plasmolysis

The process in which plant cells are placed in a hypertonic solution and therefore undergo osmosis. The cell membrane contracts and shrinks away from the cell wall.

Crenation

When an animal cell is placed in a hypertonic solution, and therefore undergo osmosis water molecules leave the cell through osmosis. Animal cells don’t have cell walls so the whole cell shrinks in size and becomes crenated.

Lysis

When an animal cell is put in a hypotonic solution and therefore the water molecules enter the cell by osmosis. The cell membrane is elastic - if the cell expands too much, the cell will burst and become lysed.

Turgid

When a cell has lots of water in it and is swollen and firm.

Flaccid

When a cell is lacking water.

Why does increased temperatures increase the rate of diffusion?

As the temperature increases, molecules gain more kinetic energy which makes them move much faster. This means the molecules have more kinetic energy to move from a region of high to low concentration, causing the rate of diffusion to increase.

What happens when there’s an even concentration in diffusion?

There is no net movement, but the molecules keep moving.

What do all molecules and ions have?

All molecules and ions have kinetic energy and can therefore move.

What will water always do in osmosis?

Water always moves in both directions across a membrane. However, water molecules are attracted to solute, so the net movement of water will be moving towards the greater concentration of solute.